diff --git a/build.gradle.kts b/build.gradle.kts
index c5de688..505c00e 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -28,7 +28,7 @@ plugins {
     alias(libs.plugins.versions)
 }
 
-version = ProjectVersion("1.0.1", BuildType.snapshot)
+version = ProjectVersion("2.0.0", BuildType.snapshot)
 group = "org.cthing"
 description = "A Java library for escaping strings for use in various languages (e.g. XML)."
 
@@ -39,9 +39,9 @@ java {
 }
 
 dependencies {
-    api(libs.jsr305)
+    api(libs.jspecify)
 
-    implementation(libs.cthingAnnots)
+    compileOnly(libs.cthingAnnots)
 
     testImplementation(libs.junitApi)
     testImplementation(libs.junitParams)
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 882dba6..8a79650 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -13,8 +13,8 @@ versions = { id = "com.github.ben-manes.versions", version = "0.51.0" }
 
 [libraries]
 assertJ = "org.assertj:assertj-core:3.26.3"
-cthingAnnots = "org.cthing:cthing-annotations:1.0.0"
-jsr305 = "com.google.code.findbugs:jsr305:3.0.2"
+cthingAnnots = "org.cthing:cthing-annotations:2.0.0"
+jspecify = "org.jspecify:jspecify:1.0.0"
 junitApi = { module = "org.junit.jupiter:junit-jupiter-api", version.ref = "junit" }
 junitEngine = { module = "org.junit.jupiter:junit-jupiter-engine", version.ref = "junit" }
 junitLauncher = "org.junit.platform:junit-platform-launcher:1.11.2"
diff --git a/src/main/java/org/cthing/escapers/CsvEscaper.java b/src/main/java/org/cthing/escapers/CsvEscaper.java
index c1615f5..ebdc386 100644
--- a/src/main/java/org/cthing/escapers/CsvEscaper.java
+++ b/src/main/java/org/cthing/escapers/CsvEscaper.java
@@ -10,9 +10,8 @@
 import java.io.UncheckedIOException;
 import java.io.Writer;
 
-import javax.annotation.WillNotClose;
-
 import org.cthing.annotations.NoCoverageGenerated;
+import org.jspecify.annotations.Nullable;
 
 
 /**
@@ -34,7 +33,8 @@ private CsvEscaper() {
      * @param charSequence String to escape
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final CharSequence charSequence) {
+    @Nullable
+    public static String escape(@Nullable final CharSequence charSequence) {
         return (charSequence == null)
                ? null : escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length());
     }
@@ -43,12 +43,11 @@ public static String escape(final CharSequence charSequence) {
      * Applies CSV escaping to the specified string and writes the result to the specified writer.
      *
      * @param charSequence String to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final CharSequence charSequence, final Writer writer) throws IOException {
+    public static void escape(@Nullable final CharSequence charSequence, final Writer writer) throws IOException {
         if (charSequence != null) {
             escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(), writer);
         }
@@ -60,7 +59,8 @@ public static void escape(final CharSequence charSequence, final Writer writer)
      * @param charArr Character array to escape
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr) {
         return (charArr == null) ? null : escape(index -> Character.codePointAt(charArr, index), 0, charArr.length);
     }
 
@@ -72,7 +72,8 @@ public static String escape(final char[] charArr) {
      * @param length Number of characters in array
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr, final int offset, final int length) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final int offset, final int length) {
         return (charArr == null) ? null : escape(index -> Character.codePointAt(charArr, index), offset, length);
     }
 
@@ -80,12 +81,11 @@ public static String escape(final char[] charArr, final int offset, final int le
      * Applies CSV escaping to the specified character array and writes the result to the specified writer.
      *
      * @param charArr Character array to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final Writer writer) throws IOException {
+    public static void escape(final char @Nullable[] charArr, final Writer writer) throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), 0, charArr.length, writer);
         }
@@ -97,12 +97,11 @@ public static void escape(final char[] charArr, final Writer writer) throws IOEx
      * @param charArr Character array to escape
      * @param offset Start index in array
      * @param length Number of characters in array
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final int offset, final int length, final Writer writer)
+    public static void escape(final char @Nullable[] charArr, final int offset, final int length, final Writer writer)
             throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), offset, length, writer);
@@ -120,11 +119,7 @@ private static String escape(final CodePointProvider codePointProvider, final in
     }
 
     private static void escape(final CodePointProvider codePointProvider, final int offset, final int length,
-                               final Writer writer)
-            throws IOException {
-        if (writer == null) {
-            throw new IllegalArgumentException("writer must not be null");
-        }
+                               final Writer writer) throws IOException {
         if (length < 0) {
             throw new IndexOutOfBoundsException("length must be greater than or equal to 0");
         }
diff --git a/src/main/java/org/cthing/escapers/HtmlEscaper.java b/src/main/java/org/cthing/escapers/HtmlEscaper.java
index 7b315a5..ee87ffc 100644
--- a/src/main/java/org/cthing/escapers/HtmlEscaper.java
+++ b/src/main/java/org/cthing/escapers/HtmlEscaper.java
@@ -12,9 +12,8 @@
 import java.util.Set;
 import java.util.function.Function;
 
-import javax.annotation.WillNotClose;
-
 import org.cthing.annotations.NoCoverageGenerated;
+import org.jspecify.annotations.Nullable;
 
 
 /**
@@ -207,7 +206,8 @@ private HtmlEscaper() {
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final CharSequence charSequence, final Option... options) {
+    @Nullable
+    public static String escape(@Nullable final CharSequence charSequence, final Option... options) {
         return (charSequence == null)
                ? null
                : escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(),
@@ -221,7 +221,8 @@ public static String escape(final CharSequence charSequence, final Option... opt
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final CharSequence charSequence, final Set<Option> options) {
+    @Nullable
+    public static String escape(@Nullable final CharSequence charSequence, final Set<Option> options) {
         return (charSequence == null)
                ? null : escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(), options);
     }
@@ -230,13 +231,12 @@ public static String escape(final CharSequence charSequence, final Set<Option> o
      * Applies HTML escaping to the specified string and writes the result to the specified writer.
      *
      * @param charSequence String to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final CharSequence charSequence, final Writer writer, final Option... options)
+    public static void escape(@Nullable final CharSequence charSequence, final Writer writer, final Option... options)
             throws IOException {
         if (charSequence != null) {
             escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(), writer,
@@ -248,13 +248,12 @@ public static void escape(final CharSequence charSequence, final Writer writer,
      * Applies HTML escaping to the specified string and writes the result to the specified writer.
      *
      * @param charSequence String to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final CharSequence charSequence, final Writer writer, final Set<Option> options)
+    public static void escape(@Nullable final CharSequence charSequence, final Writer writer, final Set<Option> options)
             throws IOException {
         if (charSequence != null) {
             escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(), writer, options);
@@ -268,7 +267,8 @@ public static void escape(final CharSequence charSequence, final Writer writer,
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr, final Option... options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final Option... options) {
         return (charArr == null)
                ? null
                : escape(index -> Character.codePointAt(charArr, index), 0, charArr.length,
@@ -284,7 +284,9 @@ public static String escape(final char[] charArr, final Option... options) {
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr, final int offset, final int length, final Option... options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final int offset, final int length,
+                                final Option... options) {
         return (charArr == null)
                ? null
                : escape(index -> Character.codePointAt(charArr, index), offset, length,
@@ -298,7 +300,8 @@ public static String escape(final char[] charArr, final int offset, final int le
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr, final Set<Option> options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final Set<Option> options) {
         return (charArr == null)
                ? null : escape(index -> Character.codePointAt(charArr, index), 0, charArr.length, options);
     }
@@ -312,7 +315,9 @@ public static String escape(final char[] charArr, final Set<Option> options) {
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr, final int offset, final int length, final Set<Option> options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final int offset, final int length,
+                                final Set<Option> options) {
         return (charArr == null)
                ? null : escape(index -> Character.codePointAt(charArr, index), offset, length, options);
     }
@@ -321,13 +326,13 @@ public static String escape(final char[] charArr, final int offset, final int le
      * Applies HTML escaping to the specified character array and writes the result to the specified writer.
      *
      * @param charArr Character array to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final Writer writer, final Option... options) throws IOException {
+    public static void escape(final char @Nullable[] charArr, final Writer writer, final Option... options)
+            throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), 0, charArr.length, writer,
                    toEnumSet(HtmlEscaper.Option.class, options));
@@ -340,13 +345,12 @@ public static void escape(final char[] charArr, final Writer writer, final Optio
      * @param charArr Character array to escape
      * @param offset Start index in array
      * @param length Number of characters in array
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final int offset, final int length, final Writer writer,
+    public static void escape(final char @Nullable[] charArr, final int offset, final int length, final Writer writer,
                               final Option... options) throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), offset, length, writer,
@@ -358,13 +362,13 @@ public static void escape(final char[] charArr, final int offset, final int leng
      * Applies HTML escaping to the specified character array and writes the result to the specified writer.
      *
      * @param charArr Character array to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final Writer writer, final Set<Option> options) throws IOException {
+    public static void escape(final char @Nullable[] charArr, final Writer writer, final Set<Option> options)
+            throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), 0, charArr.length, writer, options);
         }
@@ -376,13 +380,12 @@ public static void escape(final char[] charArr, final Writer writer, final Set<O
      * @param charArr Character array to escape
      * @param offset Start index in array
      * @param length Number of characters in array
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final int offset, final int length, final Writer writer,
+    public static void escape(final char @Nullable[] charArr, final int offset, final int length, final Writer writer,
                               final Set<Option> options) throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), offset, length, writer, options);
@@ -402,9 +405,6 @@ private static String escape(final CodePointProvider codePointProvider, final in
 
     private static void escape(final CodePointProvider codePointProvider, final int offset, final int length,
                                final Writer writer, final Set<Option> options) throws IOException {
-        if (writer == null) {
-            throw new IllegalArgumentException("writer must not be null");
-        }
         if (length < 0) {
             throw new IndexOutOfBoundsException("length must be greater than or equal to 0");
         }
@@ -415,7 +415,7 @@ private static void escape(final CodePointProvider codePointProvider, final int
         final boolean useLatin1 = options.contains(Option.USE_ISO_LATIN_1_ENTITIES);
         final boolean useExtended = options.contains(Option.USE_HTML4_EXTENDED_ENTITIES);
 
-        final Function<Integer, String> findEntity;
+        final Function<Integer, @Nullable String> findEntity;
         if (!useLatin1 && !useExtended) {
             findEntity = HtmlEntities.MARKUP_SIGNIFICANT::get;
         } else {
diff --git a/src/main/java/org/cthing/escapers/JavaEscaper.java b/src/main/java/org/cthing/escapers/JavaEscaper.java
index 05e9880..7ff8817 100644
--- a/src/main/java/org/cthing/escapers/JavaEscaper.java
+++ b/src/main/java/org/cthing/escapers/JavaEscaper.java
@@ -11,9 +11,8 @@
 import java.io.Writer;
 import java.util.Set;
 
-import javax.annotation.WillNotClose;
-
 import org.cthing.annotations.NoCoverageGenerated;
+import org.jspecify.annotations.Nullable;
 
 
 /**
@@ -151,7 +150,8 @@ private JavaEscaper() {
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final CharSequence charSequence, final Option... options) {
+    @Nullable
+    public static String escape(@Nullable final CharSequence charSequence, final Option... options) {
         return (charSequence == null)
                ? null
                : escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(),
@@ -165,7 +165,8 @@ public static String escape(final CharSequence charSequence, final Option... opt
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final CharSequence charSequence, final Set<Option> options) {
+    @Nullable
+    public static String escape(@Nullable final CharSequence charSequence, final Set<Option> options) {
         return (charSequence == null)
                ? null
                : escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(), options);
@@ -175,13 +176,12 @@ public static String escape(final CharSequence charSequence, final Set<Option> o
      * Applies JSON escaping to the specified string and writes the result to the specified writer.
      *
      * @param charSequence String to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final CharSequence charSequence, final Writer writer, final Option... options)
+    public static void escape(@Nullable final CharSequence charSequence, final Writer writer, final Option... options)
             throws IOException {
         if (charSequence != null) {
             escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(), writer,
@@ -193,13 +193,12 @@ public static void escape(final CharSequence charSequence, final Writer writer,
      * Applies JSON escaping to the specified string and writes the result to the specified writer.
      *
      * @param charSequence String to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final CharSequence charSequence, final Writer writer, final Set<Option> options)
+    public static void escape(@Nullable final CharSequence charSequence, final Writer writer, final Set<Option> options)
             throws IOException {
         if (charSequence != null) {
             escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(), writer, options);
@@ -213,7 +212,8 @@ public static void escape(final CharSequence charSequence, final Writer writer,
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr, final Option... options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final Option... options) {
         return (charArr == null)
                ? null
                : escape(index -> Character.codePointAt(charArr, index), 0, charArr.length,
@@ -229,7 +229,9 @@ public static String escape(final char[] charArr, final Option... options) {
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr, final int offset, final int length, final Option... options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final int offset, final int length,
+                                final Option... options) {
         return (charArr == null)
                ? null
                : escape(index -> Character.codePointAt(charArr, index), offset, length,
@@ -243,7 +245,8 @@ public static String escape(final char[] charArr, final int offset, final int le
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr, final Set<Option> options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final Set<Option> options) {
         return (charArr == null)
                ? null
                : escape(index -> Character.codePointAt(charArr, index), 0, charArr.length, options);
@@ -258,7 +261,9 @@ public static String escape(final char[] charArr, final Set<Option> options) {
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr, final int offset, final int length, final Set<Option> options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final int offset, final int length,
+                                final Set<Option> options) {
         return (charArr == null)
                ? null
                : escape(index -> Character.codePointAt(charArr, index), offset, length, options);
@@ -268,13 +273,13 @@ public static String escape(final char[] charArr, final int offset, final int le
      * Applies JSON escaping to the specified character array and writes the result to the specified writer.
      *
      * @param charArr Character array to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final Writer writer, final Option... options) throws IOException {
+    public static void escape(final char @Nullable[] charArr, final Writer writer, final Option... options)
+            throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), 0, charArr.length, writer,
                    toEnumSet(JavaEscaper.Option.class, options));
@@ -287,13 +292,12 @@ public static void escape(final char[] charArr, final Writer writer, final Optio
      * @param charArr Character array to escape
      * @param offset Start index in array
      * @param length Number of characters in array
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final int offset, final int length, final Writer writer,
+    public static void escape(final char @Nullable[] charArr, final int offset, final int length, final Writer writer,
                               final Option... options) throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), offset, length, writer,
@@ -305,13 +309,13 @@ public static void escape(final char[] charArr, final int offset, final int leng
      * Applies JSON escaping to the specified character array and writes the result to the specified writer.
      *
      * @param charArr Character array to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final Writer writer, final Set<Option> options) throws IOException {
+    public static void escape(final char @Nullable[] charArr, final Writer writer, final Set<Option> options)
+            throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), 0, charArr.length, writer, options);
         }
@@ -323,13 +327,12 @@ public static void escape(final char[] charArr, final Writer writer, final Set<O
      * @param charArr Character array to escape
      * @param offset Start index in array
      * @param length Number of characters in array
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final int offset, final int length, final Writer writer,
+    public static void escape(final char @Nullable[] charArr, final int offset, final int length, final Writer writer,
                               final Set<Option> options) throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), offset, length, writer, options);
@@ -349,9 +352,6 @@ private static String escape(final CodePointProvider codePointProvider, final in
 
     private static void escape(final CodePointProvider codePointProvider, final int offset, final int length,
                                final Writer writer, final Set<Option> options) throws IOException {
-        if (writer == null) {
-            throw new IllegalArgumentException("writer must not be null");
-        }
         if (length < 0) {
             throw new IndexOutOfBoundsException("length must be greater than or equal to 0");
         }
diff --git a/src/main/java/org/cthing/escapers/JavaScriptEscaper.java b/src/main/java/org/cthing/escapers/JavaScriptEscaper.java
index 908708f..6e0fade 100644
--- a/src/main/java/org/cthing/escapers/JavaScriptEscaper.java
+++ b/src/main/java/org/cthing/escapers/JavaScriptEscaper.java
@@ -11,9 +11,8 @@
 import java.io.Writer;
 import java.util.Set;
 
-import javax.annotation.WillNotClose;
-
 import org.cthing.annotations.NoCoverageGenerated;
+import org.jspecify.annotations.Nullable;
 
 
 /**
@@ -154,7 +153,8 @@ private JavaScriptEscaper() {
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final CharSequence charSequence, final Option... options) {
+    @Nullable
+    public static String escape(@Nullable final CharSequence charSequence, final Option... options) {
         return (charSequence == null)
                ? null
                : escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(),
@@ -168,7 +168,8 @@ public static String escape(final CharSequence charSequence, final Option... opt
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final CharSequence charSequence, final Set<Option> options) {
+    @Nullable
+    public static String escape(@Nullable final CharSequence charSequence, final Set<Option> options) {
         return (charSequence == null)
                ? null
                : escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(), options);
@@ -178,13 +179,12 @@ public static String escape(final CharSequence charSequence, final Set<Option> o
      * Applies JavaScript escaping to the specified string and writes the result to the specified writer.
      *
      * @param charSequence String to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final CharSequence charSequence, final Writer writer, final Option... options)
+    public static void escape(@Nullable final CharSequence charSequence, final Writer writer, final Option... options)
             throws IOException {
         if (charSequence != null) {
             escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(), writer,
@@ -196,13 +196,12 @@ public static void escape(final CharSequence charSequence, final Writer writer,
      * Applies JavaScript escaping to the specified string and writes the result to the specified writer.
      *
      * @param charSequence String to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final CharSequence charSequence, final Writer writer, final Set<Option> options)
+    public static void escape(@Nullable final CharSequence charSequence, final Writer writer, final Set<Option> options)
             throws IOException {
         if (charSequence != null) {
             escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(), writer, options);
@@ -216,7 +215,8 @@ public static void escape(final CharSequence charSequence, final Writer writer,
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr, final Option... options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final Option... options) {
         return (charArr == null)
                ? null
                : escape(index -> Character.codePointAt(charArr, index), 0, charArr.length,
@@ -232,7 +232,9 @@ public static String escape(final char[] charArr, final Option... options) {
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr, final int offset, final int length, final Option... options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final int offset, final int length,
+                                final Option... options) {
         return (charArr == null)
                ? null
                : escape(index -> Character.codePointAt(charArr, index), offset, length,
@@ -246,7 +248,8 @@ public static String escape(final char[] charArr, final int offset, final int le
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr, final Set<Option> options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final Set<Option> options) {
         return (charArr == null)
                ? null : escape(index -> Character.codePointAt(charArr, index), 0, charArr.length, options);
     }
@@ -260,7 +263,9 @@ public static String escape(final char[] charArr, final Set<Option> options) {
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr, final int offset, final int length, final Set<Option> options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final int offset, final int length,
+                                final Set<Option> options) {
         return (charArr == null)
                ? null : escape(index -> Character.codePointAt(charArr, index), offset, length, options);
     }
@@ -269,13 +274,13 @@ public static String escape(final char[] charArr, final int offset, final int le
      * Applies JavaScript escaping to the specified character array and writes the result to the specified writer.
      *
      * @param charArr Character array to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final Writer writer, final Option... options) throws IOException {
+    public static void escape(final char @Nullable[] charArr, final Writer writer, final Option... options)
+            throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), 0, charArr.length, writer,
                    toEnumSet(JavaScriptEscaper.Option.class, options));
@@ -288,13 +293,12 @@ public static void escape(final char[] charArr, final Writer writer, final Optio
      * @param charArr Character array to escape
      * @param offset Start index in array
      * @param length Number of characters in array
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final int offset, final int length, final Writer writer,
+    public static void escape(final char @Nullable[] charArr, final int offset, final int length, final Writer writer,
                               final Option... options) throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), offset, length, writer,
@@ -306,13 +310,13 @@ public static void escape(final char[] charArr, final int offset, final int leng
      * Applies JavaScript escaping to the specified character array and writes the result to the specified writer.
      *
      * @param charArr Character array to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final Writer writer, final Set<Option> options) throws IOException {
+    public static void escape(final char @Nullable[] charArr, final Writer writer, final Set<Option> options)
+            throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), 0, charArr.length, writer, options);
         }
@@ -324,13 +328,12 @@ public static void escape(final char[] charArr, final Writer writer, final Set<O
      * @param charArr Character array to escape
      * @param offset Start index in array
      * @param length Number of characters in array
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final int offset, final int length, final Writer writer,
+    public static void escape(final char @Nullable[] charArr, final int offset, final int length, final Writer writer,
                               final Set<Option> options) throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), offset, length, writer, options);
@@ -350,9 +353,6 @@ private static String escape(final CodePointProvider codePointProvider, final in
 
     private static void escape(final CodePointProvider codePointProvider, final int offset, final int length,
                                final Writer writer, final Set<Option> options) throws IOException {
-        if (writer == null) {
-            throw new IllegalArgumentException("writer must not be null");
-        }
         if (length < 0) {
             throw new IndexOutOfBoundsException("length must be greater than or equal to 0");
         }
diff --git a/src/main/java/org/cthing/escapers/JsonEscaper.java b/src/main/java/org/cthing/escapers/JsonEscaper.java
index a4d16b1..78f12d6 100644
--- a/src/main/java/org/cthing/escapers/JsonEscaper.java
+++ b/src/main/java/org/cthing/escapers/JsonEscaper.java
@@ -11,9 +11,8 @@
 import java.io.Writer;
 import java.util.Set;
 
-import javax.annotation.WillNotClose;
-
 import org.cthing.annotations.NoCoverageGenerated;
+import org.jspecify.annotations.Nullable;
 
 
 /**
@@ -144,7 +143,8 @@ private JsonEscaper() {
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final CharSequence charSequence, final Option... options) {
+    @Nullable
+    public static String escape(@Nullable final CharSequence charSequence, final Option... options) {
         return (charSequence == null)
                ? null
                : escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(),
@@ -158,7 +158,8 @@ public static String escape(final CharSequence charSequence, final Option... opt
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final CharSequence charSequence, final Set<Option> options) {
+    @Nullable
+    public static String escape(@Nullable final CharSequence charSequence, final Set<Option> options) {
         return (charSequence == null)
                ? null
                : escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(), options);
@@ -168,13 +169,12 @@ public static String escape(final CharSequence charSequence, final Set<Option> o
      * Applies JSON escaping to the specified string and writes the result to the specified writer.
      *
      * @param charSequence String to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final CharSequence charSequence, final Writer writer, final Option... options)
+    public static void escape(@Nullable final CharSequence charSequence, final Writer writer, final Option... options)
             throws IOException {
         if (charSequence != null) {
             escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(), writer,
@@ -186,13 +186,12 @@ public static void escape(final CharSequence charSequence, final Writer writer,
      * Applies JSON escaping to the specified string and writes the result to the specified writer.
      *
      * @param charSequence String to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final CharSequence charSequence, final Writer writer, final Set<Option> options)
+    public static void escape(@Nullable final CharSequence charSequence, final Writer writer, final Set<Option> options)
             throws IOException {
         if (charSequence != null) {
             escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(), writer, options);
@@ -206,7 +205,8 @@ public static void escape(final CharSequence charSequence, final Writer writer,
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr, final Option... options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final Option... options) {
         return (charArr == null)
                ? null
                : escape(index -> Character.codePointAt(charArr, index), 0, charArr.length,
@@ -222,7 +222,9 @@ public static String escape(final char[] charArr, final Option... options) {
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr, final int offset, final int length, final Option... options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final int offset, final int length,
+                                final Option... options) {
         return (charArr == null)
                ? null
                : escape(index -> Character.codePointAt(charArr, index), offset, length,
@@ -236,7 +238,8 @@ public static String escape(final char[] charArr, final int offset, final int le
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr, final Set<Option> options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final Set<Option> options) {
         return (charArr == null)
                ? null : escape(index -> Character.codePointAt(charArr, index), 0, charArr.length, options);
     }
@@ -250,7 +253,9 @@ public static String escape(final char[] charArr, final Set<Option> options) {
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final char[] charArr, final int offset, final int length, final Set<Option> options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final int offset, final int length,
+                                final Set<Option> options) {
         return (charArr == null)
                ? null : escape(index -> Character.codePointAt(charArr, index), offset, length, options);
     }
@@ -259,13 +264,13 @@ public static String escape(final char[] charArr, final int offset, final int le
      * Applies JSON escaping to the specified character array and writes the result to the specified writer.
      *
      * @param charArr Character array to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final Writer writer, final Option... options) throws IOException {
+    public static void escape(final char @Nullable[] charArr, final Writer writer, final Option... options)
+            throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), 0, charArr.length, writer,
                    toEnumSet(JsonEscaper.Option.class, options));
@@ -278,13 +283,12 @@ public static void escape(final char[] charArr, final Writer writer, final Optio
      * @param charArr Character array to escape
      * @param offset Start index in array
      * @param length Number of characters in array
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final int offset, final int length, final Writer writer,
+    public static void escape(final char @Nullable[] charArr, final int offset, final int length, final Writer writer,
                               final Option... options) throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), offset, length, writer,
@@ -296,13 +300,13 @@ public static void escape(final char[] charArr, final int offset, final int leng
      * Applies JSON escaping to the specified character array and writes the result to the specified writer.
      *
      * @param charArr Character array to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final Writer writer, final Set<Option> options) throws IOException {
+    public static void escape(final char @Nullable[] charArr, final Writer writer, final Set<Option> options)
+            throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), 0, charArr.length, writer, options);
         }
@@ -314,13 +318,12 @@ public static void escape(final char[] charArr, final Writer writer, final Set<O
      * @param charArr Character array to escape
      * @param offset Start index in array
      * @param length Number of characters in array
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final int offset, final int length, final Writer writer,
+    public static void escape(final char @Nullable[] charArr, final int offset, final int length, final Writer writer,
                               final Set<Option> options) throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), offset, length, writer, options);
@@ -340,9 +343,6 @@ private static String escape(final CodePointProvider codePointProvider, final in
 
     private static void escape(final CodePointProvider codePointProvider, final int offset, final int length,
                                final Writer writer, final Set<Option> options) throws IOException {
-        if (writer == null) {
-            throw new IllegalArgumentException("writer must not be null");
-        }
         if (length < 0) {
             throw new IndexOutOfBoundsException("length must be greater than or equal to 0");
         }
diff --git a/src/main/java/org/cthing/escapers/XmlEscaper.java b/src/main/java/org/cthing/escapers/XmlEscaper.java
index 6f955c4..7480a68 100644
--- a/src/main/java/org/cthing/escapers/XmlEscaper.java
+++ b/src/main/java/org/cthing/escapers/XmlEscaper.java
@@ -11,9 +11,8 @@
 import java.io.Writer;
 import java.util.Set;
 
-import javax.annotation.WillNotClose;
-
 import org.cthing.annotations.NoCoverageGenerated;
+import org.jspecify.annotations.Nullable;
 
 
 /**
@@ -180,7 +179,8 @@ private XmlEscaper() {
      * @return Escaped string or {@code null} if {@code null} was passed in. Note that invalid XML characters are
      *      not included in the output.
      */
-    public static String escape(final CharSequence charSequence, final Option... options) {
+    @Nullable
+    public static String escape(@Nullable final CharSequence charSequence, final Option... options) {
         return (charSequence == null)
                ? null
                : escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(),
@@ -195,7 +195,8 @@ public static String escape(final CharSequence charSequence, final Option... opt
      * @return Escaped string or {@code null} if {@code null} was passed in. Note that invalid XML characters are
      *      not included in the output.
      */
-    public static String escape(final CharSequence charSequence, final Set<Option> options) {
+    @Nullable
+    public static String escape(@Nullable final CharSequence charSequence, final Set<Option> options) {
         return (charSequence == null)
                ? null
                : escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(), options);
@@ -206,13 +207,12 @@ public static String escape(final CharSequence charSequence, final Set<Option> o
      * invalid XML characters are not included in the output.
      *
      * @param charSequence String to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final CharSequence charSequence, final Writer writer, final Option... options)
+    public static void escape(@Nullable final CharSequence charSequence, final Writer writer, final Option... options)
             throws IOException {
         if (charSequence != null) {
             escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(), writer,
@@ -225,13 +225,12 @@ public static void escape(final CharSequence charSequence, final Writer writer,
      * invalid XML characters are not included in the output.
      *
      * @param charSequence String to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final CharSequence charSequence, final Writer writer, final Set<Option> options)
+    public static void escape(@Nullable final CharSequence charSequence, final Writer writer, final Set<Option> options)
             throws IOException {
         if (charSequence != null) {
             escape(index -> Character.codePointAt(charSequence, index), 0, charSequence.length(), writer, options);
@@ -246,7 +245,8 @@ public static void escape(final CharSequence charSequence, final Writer writer,
      * @return Escaped string or {@code null} if {@code null} was passed in. Note that invalid XML characters are
      *      not included in the output.
      */
-    public static String escape(final char[] charArr, final Option... options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final Option... options) {
         return (charArr == null)
                ? null
                : escape(index -> Character.codePointAt(charArr, index), 0, charArr.length,
@@ -263,7 +263,9 @@ public static String escape(final char[] charArr, final Option... options) {
      * @return Escaped string or {@code null} if {@code null} was passed in. Note that invalid XML characters are
      *      not included in the output.
      */
-    public static String escape(final char[] charArr, final int offset, final int length, final Option... options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final int offset, final int length,
+                                final Option... options) {
         return (charArr == null)
                ? null
                : escape(index -> Character.codePointAt(charArr, index), offset, length,
@@ -278,7 +280,8 @@ public static String escape(final char[] charArr, final int offset, final int le
      * @return Escaped string or {@code null} if {@code null} was passed in. Note that invalid XML characters are
      *      not included in the output.
      */
-    public static String escape(final char[] charArr, final Set<Option> options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final Set<Option> options) {
         return (charArr == null)
                ? null : escape(index -> Character.codePointAt(charArr, index), 0, charArr.length, options);
     }
@@ -293,7 +296,9 @@ public static String escape(final char[] charArr, final Set<Option> options) {
      * @return Escaped string or {@code null} if {@code null} was passed in. Note that invalid XML characters are
      *      not included in the output.
      */
-    public static String escape(final char[] charArr, final int offset, final int length, final Set<Option> options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final int offset, final int length,
+                                final Set<Option> options) {
         return (charArr == null)
                ? null : escape(index -> Character.codePointAt(charArr, index), offset, length, options);
     }
@@ -303,13 +308,13 @@ public static String escape(final char[] charArr, final int offset, final int le
      * invalid XML characters are not included in the output.
      *
      * @param charArr Character array to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final Writer writer, final Option... options) throws IOException {
+    public static void escape(final char @Nullable[] charArr, final Writer writer, final Option... options)
+            throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), 0, charArr.length, writer,
                    toEnumSet(XmlEscaper.Option.class, options));
@@ -323,13 +328,12 @@ public static void escape(final char[] charArr, final Writer writer, final Optio
      * @param charArr Character array to escape
      * @param offset Start index in array
      * @param length Number of characters in array
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final int offset, final int length, final Writer writer,
+    public static void escape(final char @Nullable[] charArr, final int offset, final int length, final Writer writer,
                               final Option... options) throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), offset, length, writer,
@@ -342,13 +346,13 @@ public static void escape(final char[] charArr, final int offset, final int leng
      * invalid XML characters are not included in the output.
      *
      * @param charArr Character array to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final Writer writer, final Set<Option> options) throws IOException {
+    public static void escape(final char @Nullable[] charArr, final Writer writer, final Set<Option> options)
+            throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), 0, charArr.length, writer, options);
         }
@@ -361,13 +365,12 @@ public static void escape(final char[] charArr, final Writer writer, final Set<O
      * @param charArr Character array to escape
      * @param offset Start index in array
      * @param length Number of characters in array
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final int offset, final int length, final Writer writer,
+    public static void escape(final char @Nullable[] charArr, final int offset, final int length, final Writer writer,
                               final Set<Option> options) throws IOException {
         if (charArr != null) {
             escape(index -> Character.codePointAt(charArr, index), offset, length, writer, options);
@@ -387,9 +390,6 @@ private static String escape(final CodePointProvider codePointProvider, final in
 
     private static void escape(final CodePointProvider codePointProvider, final int offset, final int length,
                                final Writer writer, final Set<Option> options) throws IOException {
-        if (writer == null) {
-            throw new IllegalArgumentException("writer must not be null");
-        }
         if (length < 0) {
             throw new IndexOutOfBoundsException("length must be greater than or equal to 0");
         }
diff --git a/src/main/java/org/cthing/escapers/YamlEscaper.java b/src/main/java/org/cthing/escapers/YamlEscaper.java
index 6cc1a19..7ad68ab 100644
--- a/src/main/java/org/cthing/escapers/YamlEscaper.java
+++ b/src/main/java/org/cthing/escapers/YamlEscaper.java
@@ -11,10 +11,9 @@
 import java.io.Writer;
 import java.util.Set;
 
-import javax.annotation.WillNotClose;
-
 import org.cthing.annotations.AccessForTesting;
 import org.cthing.annotations.NoCoverageGenerated;
+import org.jspecify.annotations.Nullable;
 
 
 /**
@@ -235,7 +234,8 @@ private YamlEscaper() {
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final CharSequence charSequence, final Option... options) {
+    @Nullable
+    public static String escape(@Nullable final CharSequence charSequence, final Option... options) {
         return (charSequence == null)
                ? null : escape(charSequence.toString(), toEnumSet(YamlEscaper.Option.class, options));
     }
@@ -247,7 +247,8 @@ public static String escape(final CharSequence charSequence, final Option... opt
      * @param options Escaping options
      * @return Escaped string or {@code null} if {@code null} was passed in.
      */
-    public static String escape(final CharSequence charSequence, final Set<Option> options) {
+    @Nullable
+    public static String escape(@Nullable final CharSequence charSequence, final Set<Option> options) {
         return (charSequence == null) ? null : escape(charSequence.toString(), options);
     }
 
@@ -255,13 +256,12 @@ public static String escape(final CharSequence charSequence, final Set<Option> o
      * Applies YAML escaping to the specified string and writes the result to the specified writer.
      *
      * @param charSequence String to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final CharSequence charSequence, final Writer writer, final Option... options)
+    public static void escape(@Nullable final CharSequence charSequence, final Writer writer, final Option... options)
             throws IOException {
         if (charSequence != null) {
             escape(charSequence.toString(), writer, toEnumSet(YamlEscaper.Option.class, options));
@@ -272,13 +272,12 @@ public static void escape(final CharSequence charSequence, final Writer writer,
      * Applies YAML escaping to the specified string and writes the result to the specified writer.
      *
      * @param charSequence String to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final CharSequence charSequence, final Writer writer, final Set<Option> options)
+    public static void escape(@Nullable final CharSequence charSequence, final Writer writer, final Set<Option> options)
             throws IOException {
         if (charSequence != null) {
             escape(charSequence.toString(), writer, options);
@@ -293,7 +292,8 @@ public static void escape(final CharSequence charSequence, final Writer writer,
      * @return Escaped string or {@code null} if {@code null} was passed in. Note that invalid XML characters are
      *      not included in the output.
      */
-    public static String escape(final char[] charArr, final Option... options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final Option... options) {
         return (charArr == null) ? null : escape(new String(charArr), toEnumSet(YamlEscaper.Option.class, options));
     }
 
@@ -307,7 +307,9 @@ public static String escape(final char[] charArr, final Option... options) {
      * @return Escaped string or {@code null} if {@code null} was passed in. Note that invalid XML characters are
      *      not included in the output.
      */
-    public static String escape(final char[] charArr, final int offset, final int length, final Option... options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final int offset, final int length,
+                                final Option... options) {
         return (charArr == null) ? null : escape(new String(charArr, offset, length),
                                                  toEnumSet(YamlEscaper.Option.class, options));
     }
@@ -320,7 +322,8 @@ public static String escape(final char[] charArr, final int offset, final int le
      * @return Escaped string or {@code null} if {@code null} was passed in. Note that invalid XML characters are
      *      not included in the output.
      */
-    public static String escape(final char[] charArr, final Set<Option> options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final Set<Option> options) {
         return (charArr == null) ? null : escape(new String(charArr), options);
     }
 
@@ -334,7 +337,9 @@ public static String escape(final char[] charArr, final Set<Option> options) {
      * @return Escaped string or {@code null} if {@code null} was passed in. Note that invalid XML characters are
      *      not included in the output.
      */
-    public static String escape(final char[] charArr, final int offset, final int length, final Set<Option> options) {
+    @Nullable
+    public static String escape(final char @Nullable[] charArr, final int offset, final int length,
+                                final Set<Option> options) {
         return (charArr == null) ? null : escape(new String(charArr, offset, length), options);
     }
 
@@ -342,13 +347,13 @@ public static String escape(final char[] charArr, final int offset, final int le
      * Applies YAML escaping to the specified character array and writes the result to the specified writer.
      *
      * @param charArr Character array to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final Writer writer, final Option... options) throws IOException {
+    public static void escape(final char @Nullable[] charArr, final Writer writer, final Option... options)
+            throws IOException {
         if (charArr != null) {
             escape(new String(charArr), writer, toEnumSet(YamlEscaper.Option.class, options));
         }
@@ -360,13 +365,12 @@ public static void escape(final char[] charArr, final Writer writer, final Optio
      * @param charArr Character array to escape
      * @param offset Start index in array
      * @param length Number of characters in array
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final int offset, final int length, final Writer writer,
+    public static void escape(final char @Nullable[] charArr, final int offset, final int length, final Writer writer,
                               final Option... options) throws IOException {
         if (charArr != null) {
             escape(new String(charArr, offset, length), writer, toEnumSet(YamlEscaper.Option.class, options));
@@ -377,13 +381,13 @@ public static void escape(final char[] charArr, final int offset, final int leng
      * Applies YAML escaping to the specified character array and writes the result to the specified writer.
      *
      * @param charArr Character array to escape
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final Writer writer, final Set<Option> options) throws IOException {
+    public static void escape(final char @Nullable[] charArr, final Writer writer, final Set<Option> options)
+            throws IOException {
         if (charArr != null) {
             escape(new String(charArr), writer, options);
         }
@@ -394,13 +398,12 @@ public static void escape(final char[] charArr, final Writer writer, final Set<O
      * @param charArr Character array to escape
      * @param offset Start index in array
      * @param length Number of characters in array
-     * @param writer Writer to which the escaped string is written
+     * @param writer Writer to which the escaped string is written. Will not be closed by this method.
      * @param options Escaping options
      * @throws IOException if there was a problem writing the escaped string
      * @throws IllegalArgumentException if the writer is {@code null}
      */
-    @WillNotClose
-    public static void escape(final char[] charArr, final int offset, final int length, final Writer writer,
+    public static void escape(final char @Nullable[] charArr, final int offset, final int length, final Writer writer,
                               final Set<Option> options) throws IOException {
         if (charArr != null) {
             escape(new String(charArr, offset, length), writer, options);
@@ -417,12 +420,7 @@ private static String escape(final String str, final Set<Option> options) {
         }
     }
 
-    private static void escape(final String str, final Writer writer, final Set<Option> options)
-            throws IOException {
-        if (writer == null) {
-            throw new IllegalArgumentException("writer must not be null");
-        }
-
+    private static void escape(final String str, final Writer writer, final Set<Option> options) throws IOException {
         final boolean escapeNonAscii = options.contains(Option.ESCAPE_NON_ASCII);
 
         final Quoting quoting = requiresQuotes(str, escapeNonAscii);
diff --git a/src/main/java/org/cthing/escapers/package-info.java b/src/main/java/org/cthing/escapers/package-info.java
index 8ff725b..454ed1e 100644
--- a/src/main/java/org/cthing/escapers/package-info.java
+++ b/src/main/java/org/cthing/escapers/package-info.java
@@ -15,4 +15,7 @@
  *     <li>YAML</li>
  * </ul>
  */
+@NullMarked
 package org.cthing.escapers;
+
+import org.jspecify.annotations.NullMarked;
diff --git a/src/test/java/org/cthing/escapers/CsvEscaperTest.java b/src/test/java/org/cthing/escapers/CsvEscaperTest.java
index 67c63f6..c3c889e 100644
--- a/src/test/java/org/cthing/escapers/CsvEscaperTest.java
+++ b/src/test/java/org/cthing/escapers/CsvEscaperTest.java
@@ -15,7 +15,6 @@
 import org.junit.jupiter.params.provider.MethodSource;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.assertj.core.api.Assertions.assertThatIndexOutOfBoundsException;
 import static org.junit.jupiter.params.provider.Arguments.arguments;
 
@@ -71,9 +70,6 @@ public void testErrors() throws IOException {
         CsvEscaper.escape((char[])null, writer);
         assertThat(writer.toString()).isEmpty();
 
-        assertThatIllegalArgumentException().isThrownBy(() -> CsvEscaper.escape("hello", null));
-        assertThatIllegalArgumentException().isThrownBy(() -> CsvEscaper.escape("hello".toCharArray(), null));
-
         assertThatIndexOutOfBoundsException().isThrownBy(() -> CsvEscaper.escape("hello".toCharArray(), -1, 3));
         assertThatIndexOutOfBoundsException().isThrownBy(() -> CsvEscaper.escape("hello".toCharArray(), 0, 20));
         assertThatIndexOutOfBoundsException().isThrownBy(() -> CsvEscaper.escape("hello".toCharArray(), 0, -1));
diff --git a/src/test/java/org/cthing/escapers/HtmlEscaperTest.java b/src/test/java/org/cthing/escapers/HtmlEscaperTest.java
index 3eca1e9..8b30d5d 100644
--- a/src/test/java/org/cthing/escapers/HtmlEscaperTest.java
+++ b/src/test/java/org/cthing/escapers/HtmlEscaperTest.java
@@ -7,7 +7,6 @@
 
 import java.io.IOException;
 import java.io.StringWriter;
-import java.io.Writer;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -22,7 +21,6 @@
 import org.junit.jupiter.params.provider.MethodSource;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.assertj.core.api.Assertions.assertThatIndexOutOfBoundsException;
 import static org.cthing.escapers.HtmlEscaper.Option;
 import static org.junit.jupiter.params.provider.Arguments.arguments;
@@ -189,9 +187,6 @@ public void testErrors() throws IOException {
         HtmlEscaper.escape((char[])null, writer);
         assertThat(writer.toString()).isEmpty();
 
-        assertThatIllegalArgumentException().isThrownBy(() -> HtmlEscaper.escape("hello", (Writer)null));
-        assertThatIllegalArgumentException().isThrownBy(() -> HtmlEscaper.escape("hello".toCharArray(), (Writer)null));
-
         assertThatIndexOutOfBoundsException().isThrownBy(() -> HtmlEscaper.escape("hello".toCharArray(), -1, 3));
         assertThatIndexOutOfBoundsException().isThrownBy(() -> HtmlEscaper.escape("hello".toCharArray(), 0, 20));
         assertThatIndexOutOfBoundsException().isThrownBy(() -> HtmlEscaper.escape("hello".toCharArray(), 0, -1));
diff --git a/src/test/java/org/cthing/escapers/JavaEscaperTest.java b/src/test/java/org/cthing/escapers/JavaEscaperTest.java
index 5f47674..9bfe88b 100644
--- a/src/test/java/org/cthing/escapers/JavaEscaperTest.java
+++ b/src/test/java/org/cthing/escapers/JavaEscaperTest.java
@@ -7,7 +7,6 @@
 
 import java.io.IOException;
 import java.io.StringWriter;
-import java.io.Writer;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -22,7 +21,6 @@
 import org.junit.jupiter.params.provider.MethodSource;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.assertj.core.api.Assertions.assertThatIndexOutOfBoundsException;
 import static org.cthing.escapers.JavaEscaper.Option;
 import static org.junit.jupiter.params.provider.Arguments.arguments;
@@ -194,9 +192,6 @@ public void testErrors() throws IOException {
         JavaEscaper.escape((char[])null, writer);
         assertThat(writer.toString()).isEmpty();
 
-        assertThatIllegalArgumentException().isThrownBy(() -> JavaEscaper.escape("hello", (Writer)null));
-        assertThatIllegalArgumentException().isThrownBy(() -> JavaEscaper.escape("hello".toCharArray(), (Writer)null));
-
         assertThatIndexOutOfBoundsException().isThrownBy(() -> JavaEscaper.escape("hello".toCharArray(), -1, 3));
         assertThatIndexOutOfBoundsException().isThrownBy(() -> JavaEscaper.escape("hello".toCharArray(), 0, 20));
         assertThatIndexOutOfBoundsException().isThrownBy(() -> JavaEscaper.escape("hello".toCharArray(), 0, -1));
diff --git a/src/test/java/org/cthing/escapers/JavaScriptEscaperTest.java b/src/test/java/org/cthing/escapers/JavaScriptEscaperTest.java
index b0b5b67..4e7589d 100644
--- a/src/test/java/org/cthing/escapers/JavaScriptEscaperTest.java
+++ b/src/test/java/org/cthing/escapers/JavaScriptEscaperTest.java
@@ -7,7 +7,6 @@
 
 import java.io.IOException;
 import java.io.StringWriter;
-import java.io.Writer;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -22,7 +21,6 @@
 import org.junit.jupiter.params.provider.MethodSource;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.assertj.core.api.Assertions.assertThatIndexOutOfBoundsException;
 import static org.cthing.escapers.JavaScriptEscaper.Option;
 import static org.junit.jupiter.params.provider.Arguments.arguments;
@@ -176,10 +174,6 @@ public void testErrors() throws IOException {
         JavaScriptEscaper.escape((char[])null, writer);
         assertThat(writer.toString()).isEmpty();
 
-        assertThatIllegalArgumentException().isThrownBy(() -> JavaScriptEscaper.escape("hello", (Writer)null));
-        assertThatIllegalArgumentException().isThrownBy(() -> JavaScriptEscaper.escape("hello".toCharArray(),
-                                                                                       (Writer)null));
-
         assertThatIndexOutOfBoundsException().isThrownBy(() -> JavaScriptEscaper.escape("hello".toCharArray(), -1, 3));
         assertThatIndexOutOfBoundsException().isThrownBy(() -> JavaScriptEscaper.escape("hello".toCharArray(), 0, 20));
         assertThatIndexOutOfBoundsException().isThrownBy(() -> JavaScriptEscaper.escape("hello".toCharArray(), 0, -1));
diff --git a/src/test/java/org/cthing/escapers/JsonEscaperTest.java b/src/test/java/org/cthing/escapers/JsonEscaperTest.java
index 0d69d56..aa35df5 100644
--- a/src/test/java/org/cthing/escapers/JsonEscaperTest.java
+++ b/src/test/java/org/cthing/escapers/JsonEscaperTest.java
@@ -7,7 +7,6 @@
 
 import java.io.IOException;
 import java.io.StringWriter;
-import java.io.Writer;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -22,7 +21,6 @@
 import org.junit.jupiter.params.provider.MethodSource;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.assertj.core.api.Assertions.assertThatIndexOutOfBoundsException;
 import static org.cthing.escapers.JsonEscaper.Option;
 import static org.junit.jupiter.params.provider.Arguments.arguments;
@@ -168,9 +166,6 @@ public void testErrors() throws IOException {
         JsonEscaper.escape((char[])null, writer);
         assertThat(writer.toString()).isEmpty();
 
-        assertThatIllegalArgumentException().isThrownBy(() -> JsonEscaper.escape("hello", (Writer)null));
-        assertThatIllegalArgumentException().isThrownBy(() -> JsonEscaper.escape("hello".toCharArray(), (Writer)null));
-
         assertThatIndexOutOfBoundsException().isThrownBy(() -> JsonEscaper.escape("hello".toCharArray(), -1, 3));
         assertThatIndexOutOfBoundsException().isThrownBy(() -> JsonEscaper.escape("hello".toCharArray(), 0, 20));
         assertThatIndexOutOfBoundsException().isThrownBy(() -> JsonEscaper.escape("hello".toCharArray(), 0, -1));
diff --git a/src/test/java/org/cthing/escapers/XmlEscaperTest.java b/src/test/java/org/cthing/escapers/XmlEscaperTest.java
index 9db1822..2ef0d5e 100644
--- a/src/test/java/org/cthing/escapers/XmlEscaperTest.java
+++ b/src/test/java/org/cthing/escapers/XmlEscaperTest.java
@@ -7,7 +7,6 @@
 
 import java.io.IOException;
 import java.io.StringWriter;
-import java.io.Writer;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -22,7 +21,6 @@
 import org.junit.jupiter.params.provider.MethodSource;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.assertj.core.api.Assertions.assertThatIndexOutOfBoundsException;
 import static org.cthing.escapers.XmlEscaper.Option;
 import static org.junit.jupiter.params.provider.Arguments.arguments;
@@ -192,9 +190,6 @@ public void testErrors() throws IOException {
         XmlEscaper.escape((char[])null, writer);
         assertThat(writer.toString()).isEmpty();
 
-        assertThatIllegalArgumentException().isThrownBy(() -> XmlEscaper.escape("hello", (Writer)null));
-        assertThatIllegalArgumentException().isThrownBy(() -> XmlEscaper.escape("hello".toCharArray(), (Writer)null));
-
         assertThatIndexOutOfBoundsException().isThrownBy(() -> XmlEscaper.escape("hello".toCharArray(), -1, 3));
         assertThatIndexOutOfBoundsException().isThrownBy(() -> XmlEscaper.escape("hello".toCharArray(), 0, 20));
         assertThatIndexOutOfBoundsException().isThrownBy(() -> XmlEscaper.escape("hello".toCharArray(), 0, -1));
diff --git a/src/test/java/org/cthing/escapers/YamlEscaperTest.java b/src/test/java/org/cthing/escapers/YamlEscaperTest.java
index afc0265..b43a6e5 100644
--- a/src/test/java/org/cthing/escapers/YamlEscaperTest.java
+++ b/src/test/java/org/cthing/escapers/YamlEscaperTest.java
@@ -7,7 +7,6 @@
 
 import java.io.IOException;
 import java.io.StringWriter;
-import java.io.Writer;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -23,7 +22,6 @@
 import org.junit.jupiter.params.provider.MethodSource;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.assertj.core.api.Assertions.assertThatIndexOutOfBoundsException;
 import static org.cthing.escapers.YamlEscaper.Option;
 import static org.junit.jupiter.params.provider.Arguments.arguments;
@@ -265,9 +263,6 @@ public void testErrors() throws IOException {
         YamlEscaper.escape((char[])null, writer);
         assertThat(writer.toString()).isEmpty();
 
-        assertThatIllegalArgumentException().isThrownBy(() -> YamlEscaper.escape("hello", (Writer)null));
-        assertThatIllegalArgumentException().isThrownBy(() -> YamlEscaper.escape("hello".toCharArray(), (Writer)null));
-
         assertThatIndexOutOfBoundsException().isThrownBy(() -> YamlEscaper.escape("hello".toCharArray(), -1, 3));
         assertThatIndexOutOfBoundsException().isThrownBy(() -> YamlEscaper.escape("hello".toCharArray(), 0, 20));
         assertThatIndexOutOfBoundsException().isThrownBy(() -> YamlEscaper.escape("hello".toCharArray(), 0, -1));