diff --git a/examples/2048/.gitignore b/examples/2048/.gitignore
index 62b7973a6b865f..6bb72ddb213740 100644
--- a/examples/2048/.gitignore
+++ b/examples/2048/.gitignore
@@ -2,3 +2,5 @@
 2048
 main
 
+index.js
+index.wasm
diff --git a/examples/2048/README.md b/examples/2048/README.md
index ae9ce7fb1c3a49..3812d6fafd7894 100644
--- a/examples/2048/README.md
+++ b/examples/2048/README.md
@@ -28,7 +28,8 @@ Compile & run the game with `./v run examples/2048`
 
 ## Compiling to WASM
 
-1. Install Emscripten from https://emscripten.org/docs/getting_started/downloads.html
+1. Install Emscripten from:
+   https://emscripten.org/docs/getting_started/downloads.html
 
 2. Make sure that the environment in your shell is setup correctly,
    i.e. that `emcc --version` works.
@@ -39,15 +40,9 @@ Compile & run the game with `./v run examples/2048`
    ```
 
 3. Compile the game to WASM:
-
-   ```sh
-   v -skip-unused -prod -os wasm32_emscripten examples/2048/`
-   ```
-
-4. Copy the 2048 file to `index.js` (can be done once; this step will be removed soon):
-
+   (the JS file contains a loader for the .wasm file, without the extension):
    ```sh
-   cp examples/2048/2048 examples/2048/index.js
+   v -prod -os wasm32_emscripten -o examples/2048/index.js examples/2048/
    ```
 
 5. Run/test the game:
diff --git a/vlib/os/os.v b/vlib/os/os.v
index 8c30f9cfba1a86..35de856334dda3 100644
--- a/vlib/os/os.v
+++ b/vlib/os/os.v
@@ -608,7 +608,7 @@ pub fn find_abs_path_of_executable(exe_name string) !string {
 			$if trace_find_abs_path_of_executable ? {
 				dump(found_abs_path)
 			}
-			if exists(found_abs_path) && is_executable(found_abs_path) {
+			if is_file(found_abs_path) && is_executable(found_abs_path) {
 				res = found_abs_path
 				break
 			}
diff --git a/vlib/v/builder/cc.v b/vlib/v/builder/cc.v
index 802e05a23b40f8..5bce5c4495c2b1 100644
--- a/vlib/v/builder/cc.v
+++ b/vlib/v/builder/cc.v
@@ -108,6 +108,7 @@ pub enum CC {
 	icc
 	msvc
 	clang
+	emcc
 	unknown
 }
 
@@ -210,6 +211,7 @@ fn (mut v Builder) setup_ccompiler_options(ccompiler string) {
 			cc_file_name.contains('clang') || ccoptions.guessed_compiler == 'clang' { .clang }
 			cc_file_name.contains('msvc') || ccoptions.guessed_compiler == 'msvc' { .msvc }
 			cc_file_name.contains('icc') || ccoptions.guessed_compiler == 'icc' { .icc }
+			cc_file_name.contains('emcc') || ccoptions.guessed_compiler == 'emcc' { .emcc }
 			else { .unknown }
 			// vfmt on
 		}
@@ -652,7 +654,7 @@ pub fn (mut v Builder) cc() {
 	// whether to just create a .c or .js file and exit, for example: `v -o v.c cmd.v`
 	ends_with_c := v.pref.out_name.ends_with('.c')
 	ends_with_js := v.pref.out_name.ends_with('.js')
-	if ends_with_c || ends_with_js {
+	if ends_with_c || (ends_with_js && v.pref.os != .wasm32_emscripten) {
 		v.pref.skip_running = true
 		msg_mv := 'os.mv_by_cp ${os.quoted_path(v.out_name_c)} => ${os.quoted_path(v.pref.out_name)}'
 		util.timing_start(msg_mv)
diff --git a/vlib/v/pref/default.v b/vlib/v/pref/default.v
index 318bc7be8f5561..887a330d463513 100644
--- a/vlib/v/pref/default.v
+++ b/vlib/v/pref/default.v
@@ -61,7 +61,7 @@ fn (mut p Preferences) setup_os_and_arch_when_not_explicitly_set() {
 	host_os := if p.backend == .wasm { OS.wasi } else { get_host_os() }
 	if p.os == ._auto {
 		p.os = host_os
-		p.build_options << '-os ${host_os}'
+		p.build_options << '-os ${host_os.lower()}'
 	}
 
 	if !p.output_cross_c {
@@ -83,6 +83,19 @@ fn (mut p Preferences) setup_os_and_arch_when_not_explicitly_set() {
 	}
 }
 
+pub fn (mut p Preferences) defines_map_unique_keys() string {
+	mut defines_map := map[string]bool{}
+	for d in p.compile_defines {
+		defines_map[d] = true
+	}
+	for d in p.compile_defines_all {
+		defines_map[d] = true
+	}
+	keys := defines_map.keys()
+	skeys := keys.sorted()
+	return skeys.join(',')
+}
+
 pub fn (mut p Preferences) fill_with_defaults() {
 	p.setup_os_and_arch_when_not_explicitly_set()
 	p.expand_lookup_paths()
@@ -189,17 +202,20 @@ pub fn (mut p Preferences) fill_with_defaults() {
 			}
 		}
 	}
+
+	final_os := p.os.lower()
+	p.parse_define(final_os)
+
 	// Prepare the cache manager. All options that can affect the generated cached .c files
 	// should go into res.cache_manager.vopts, which is used as a salt for the cache hash.
 	vhash := @VHASH
 	p.cache_manager = vcache.new_cache_manager([
 		vhash,
 		// ensure that different v versions use separate build artefacts
-		'${p.backend} | ${p.os} | ${p.ccompiler} | ${p.is_prod} | ${p.sanitize}',
+		'${p.backend} | ${final_os} | ${p.ccompiler} | ${p.is_prod} | ${p.sanitize}',
+		p.defines_map_unique_keys(),
 		p.cflags.trim_space(),
 		p.third_party_option.trim_space(),
-		p.compile_defines_all.str(),
-		p.compile_defines.str(),
 		p.lookup_path.str(),
 	])
 	// eprintln('prefs.cache_manager: $p')
diff --git a/vlib/v/pref/os.v b/vlib/v/pref/os.v
index 9d46aac301edb5..3f19959180144b 100644
--- a/vlib/v/pref/os.v
+++ b/vlib/v/pref/os.v
@@ -131,6 +131,41 @@ pub fn os_from_string(os_str string) !OS {
 	}
 }
 
+// lower returns the name that could be used with `-os osname`, for each OS enum value
+// NOTE: it is important to not change the names here, they should match 1:1, since they
+// are used as part of the cache keys, when -usecache is passed.
+pub fn (o OS) lower() string {
+	return match o {
+		._auto { '' }
+		.linux { 'linux' }
+		.windows { 'windows' }
+		.macos { 'macos' }
+		.ios { 'ios' }
+		.freebsd { 'freebsd' }
+		.openbsd { 'openbsd' }
+		.netbsd { 'netbsd' }
+		.dragonfly { 'dragonfly' }
+		.js_node { 'js' }
+		.js_freestanding { 'js_freestanding' }
+		.js_browser { 'js_browser' }
+		.solaris { 'solaris' }
+		.serenity { 'serenity' }
+		.qnx { 'qnx' }
+		.plan9 { 'plan9' }
+		.vinix { 'vinix' }
+		.android { 'android' }
+		.termux { 'termux' }
+		.haiku { 'haiku' }
+		.raw { 'raw' }
+		.wasm32 { 'wasm32' }
+		.wasm32_wasi { 'wasm32_wasi' }
+		.wasm32_emscripten { 'wasm32_emscripten' }
+		.browser { 'browser' }
+		.wasi { 'wasi' }
+		.all { 'all' }
+	}
+}
+
 pub fn (o OS) str() string {
 	// TODO: check more thoroughly, why this method needs to exist at all,
 	// and why should it override the default autogenerated .str() method,
diff --git a/vlib/v/pref/pref.v b/vlib/v/pref/pref.v
index 3b6d10d8499c64..ad116ebb63f0d6 100644
--- a/vlib/v/pref/pref.v
+++ b/vlib/v/pref/pref.v
@@ -76,6 +76,7 @@ pub enum CompilerType {
 	gcc
 	tinyc
 	clang
+	emcc
 	mingw
 	msvc
 	cplusplus
@@ -830,7 +831,7 @@ pub fn parse_args_and_show_errors(known_external_commands []string, args []strin
 				res.build_options << '${arg}'
 			}
 			'-os' {
-				target_os := cmdline.option(args[i..], '-os', '')
+				target_os := cmdline.option(args[i..], '-os', '').to_lower_ascii()
 				i++
 				target_os_kind := os_from_string(target_os) or {
 					if target_os == 'cross' {
@@ -895,12 +896,6 @@ pub fn parse_args_and_show_errors(known_external_commands []string, args []strin
 			}
 			'-o', '-output' {
 				res.out_name = cmdline.option(args[i..], arg, '')
-				if res.out_name.ends_with('.js') {
-					res.backend = .js_node
-					res.output_cross_c = true
-				} else if res.out_name.ends_with('.o') {
-					res.is_o = true
-				}
 				if !os.is_abs_path(res.out_name) {
 					res.out_name = os.join_path(os.getwd(), res.out_name)
 				}
@@ -1053,6 +1048,18 @@ pub fn parse_args_and_show_errors(known_external_commands []string, args []strin
 		res.is_run = true
 	}
 	res.show_asserts = res.show_asserts || res.is_stats || os.getenv('VTEST_SHOW_ASSERTS') != ''
+
+	if res.os != .wasm32_emscripten {
+		if res.out_name.ends_with('.js') {
+			res.backend = .js_node
+			res.output_cross_c = true
+		}
+	}
+
+	if res.out_name.ends_with('.o') {
+		res.is_o = true
+	}
+
 	if command == 'run' && res.is_prod && os.is_atty(1) > 0 {
 		eprintln_cond(show_output && !res.is_quiet, "Note: building an optimized binary takes much longer. It shouldn't be used with `v run`.")
 		eprintln_cond(show_output && !res.is_quiet, 'Use `v run` without optimization, or build an optimized binary with -prod first, then run it separately.')
@@ -1226,6 +1233,7 @@ pub fn cc_from_string(s string) CompilerType {
 		cc.contains('tcc') || cc.contains('tinyc') { .tinyc }
 		cc.contains('gcc') { .gcc }
 		cc.contains('clang') { .clang }
+		cc.contains('emcc') { .emcc }
 		cc.contains('msvc') { .msvc }
 		cc.contains('mingw') { .mingw }
 		cc.contains('++') { .cplusplus }
diff --git a/vlib/v/pref/should_compile.v b/vlib/v/pref/should_compile.v
index a46f2202bd7cba..6e9723ec5e087e 100644
--- a/vlib/v/pref/should_compile.v
+++ b/vlib/v/pref/should_compile.v
@@ -15,28 +15,9 @@ pub fn (prefs &Preferences) should_compile_filtered_files(dir string, files_ []s
 			|| file.all_before_last('.v').all_before_last('.').ends_with('_test') {
 			continue
 		}
-		if prefs.backend in [.c, .interpret] && !prefs.should_compile_c(file) {
-			continue
-		}
-		if prefs.backend.is_js() && !prefs.should_compile_js(file) {
-			continue
-		}
-		if prefs.backend == .native && !prefs.should_compile_native(file) {
-			continue
-		}
-		if !prefs.backend.is_js() && !prefs.should_compile_asm(file) {
-			continue
-		}
-		if file.starts_with('.#') {
-			continue
-		}
-		if !prefs.prealloc && !prefs.output_cross_c && file.ends_with('prealloc.c.v') {
-			continue
-		}
-		if prefs.nofloat && file.ends_with('float.c.v') {
-			continue
-		}
+		mut is_d_notd_file := false
 		if file.contains('_d_') {
+			is_d_notd_file = true
 			if prefs.compile_defines_all.len == 0 {
 				continue
 			}
@@ -58,6 +39,7 @@ pub fn (prefs &Preferences) should_compile_filtered_files(dir string, files_ []s
 			}
 		}
 		if file.contains('_notd_') {
+			is_d_notd_file = true
 			mut allowed := true
 			for cdefine in prefs.compile_defines {
 				file_postfixes := ['_notd_${cdefine}.v', '_notd_${cdefine}.c.v']
@@ -75,6 +57,27 @@ pub fn (prefs &Preferences) should_compile_filtered_files(dir string, files_ []s
 				continue
 			}
 		}
+		if prefs.backend in [.c, .interpret] && !is_d_notd_file && !prefs.should_compile_c(file) {
+			continue
+		}
+		if prefs.backend.is_js() && !prefs.should_compile_js(file) {
+			continue
+		}
+		if prefs.backend == .native && !prefs.should_compile_native(file) {
+			continue
+		}
+		if !prefs.backend.is_js() && !prefs.should_compile_asm(file) {
+			continue
+		}
+		if file.starts_with('.#') {
+			continue
+		}
+		if !prefs.prealloc && !prefs.output_cross_c && file.ends_with('prealloc.c.v') {
+			continue
+		}
+		if prefs.nofloat && file.ends_with('float.c.v') {
+			continue
+		}
 		if prefs.exclude.len > 0 {
 			full_file_path := os.join_path(dir, file)
 			for epattern in prefs.exclude {
diff --git a/vlib/v/tests/project_compiling_to_wasm/abc_d_wasm32_emscripten.c.v b/vlib/v/tests/project_compiling_to_wasm/abc_d_wasm32_emscripten.c.v
new file mode 100644
index 00000000000000..077f9d9dbc692e
--- /dev/null
+++ b/vlib/v/tests/project_compiling_to_wasm/abc_d_wasm32_emscripten.c.v
@@ -0,0 +1,5 @@
+module main
+
+fn abc() {
+	println('This is abc_d_wasm32_emscripten.c.v')
+}
diff --git a/vlib/v/tests/project_compiling_to_wasm/abc_notd_wasm32_emscripten.c.v b/vlib/v/tests/project_compiling_to_wasm/abc_notd_wasm32_emscripten.c.v
new file mode 100644
index 00000000000000..5550b374490634
--- /dev/null
+++ b/vlib/v/tests/project_compiling_to_wasm/abc_notd_wasm32_emscripten.c.v
@@ -0,0 +1,5 @@
+module main
+
+fn abc() {
+	println('This is abc_notd_wasm32_emscripten.c.v')
+}
diff --git a/vlib/v/tests/project_compiling_to_wasm/compilation_to_wasm_works_with_d_and_notd_files_test.v b/vlib/v/tests/project_compiling_to_wasm/compilation_to_wasm_works_with_d_and_notd_files_test.v
new file mode 100644
index 00000000000000..cd1ffd2b6642d2
--- /dev/null
+++ b/vlib/v/tests/project_compiling_to_wasm/compilation_to_wasm_works_with_d_and_notd_files_test.v
@@ -0,0 +1,51 @@
+import os
+
+const vexe = os.quoted_path(@VEXE)
+const project_folder = os.dir(@FILE)
+const output_path = os.join_path(os.vtmp_dir(), 'check_wasm_works')
+
+fn testsuite_begin() {
+	os.mkdir_all(output_path) or {}
+	os.chdir(output_path)!
+	dump(os.getwd())
+}
+
+fn testsuite_end() {
+	os.system('ls -la .')
+	os.chdir(os.home_dir()) or {}
+	os.rmdir_all(output_path) or {}
+}
+
+fn test_normal() {
+	if os.user_os() == 'windows' {
+		return
+	}
+	defer { println('done ${@FN}') }
+	dump(vexe)
+	res := os.system('${os.quoted_path(vexe)} -o normal.exe ${os.quoted_path(project_folder)}')
+	assert res == 0
+	dump(res)
+	assert os.exists('normal.exe')
+	content := os.read_file('normal.exe')!
+	assert content.contains('This is abc_notd_wasm32_emscripten.c.v')
+}
+
+fn test_emcc() {
+	if os.user_os() == 'windows' {
+		return
+	}
+	defer { println('done ${@FN}') }
+	emcc := os.find_abs_path_of_executable('emcc') or {
+		println('skipping ${@FN} since `emcc` is not found')
+		return
+	}
+	dump(emcc)
+	res := os.system('${os.quoted_path(vexe)} -os wasm32_emscripten -o wasm_check.html ${os.quoted_path(project_folder)}')
+	assert res == 0
+	dump(res)
+	assert os.exists('wasm_check.html')
+	assert os.exists('wasm_check.js')
+	assert os.exists('wasm_check.wasm')
+	content := os.read_file('wasm_check.wasm')!
+	assert content.contains('This is abc_d_wasm32_emscripten.c.v')
+}
diff --git a/vlib/v/tests/project_compiling_to_wasm/main.v b/vlib/v/tests/project_compiling_to_wasm/main.v
new file mode 100644
index 00000000000000..6fb82924d5c391
--- /dev/null
+++ b/vlib/v/tests/project_compiling_to_wasm/main.v
@@ -0,0 +1,6 @@
+module main
+
+fn main() {
+	abc()
+	println('hi from main.v')
+}
diff --git a/vlib/v/tests/project_compiling_to_wasm/v.mod b/vlib/v/tests/project_compiling_to_wasm/v.mod
new file mode 100644
index 00000000000000..e69de29bb2d1d6