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<pre class='metadata'>
Title: Web Bluetooth
Repository: WebBluetoothCG/web-bluetooth
Status: CG-DRAFT
ED: https://webbluetoothcg.github.io/web-bluetooth/
Shortname: web-bluetooth
Level: 1
Translation: ja https://tkybpp.github.io/web-bluetooth-jp/
Editor: See contributors on GitHub, , https://github.com/WebBluetoothCG/web-bluetooth/graphs/contributors
Abstract: This document describes an API to discover and communicate with devices
Abstract: over the Bluetooth 4 wireless standard using the Generic Attribute Profile (GATT).
Group: web-bluetooth-cg
!Participate: <a href="https://www.w3.org/community/web-bluetooth/">Join the W3C Community Group</a>
!Participate: <a href="https://github.com/WebBluetoothCG/web-bluetooth">Fix the text through GitHub</a>
!Participate: <a href="mailto:public-web-bluetooth@w3.org">public-web-bluetooth@w3.org</a> (<a href="https://lists.w3.org/Archives/Public/public-web-bluetooth/" rel="discussion">archives</a>)
!Participate: <a href="irc://irc.w3.org:6665/#web-bluetooth">IRC: #web-bluetooth on W3C's IRC</a>
Markup Shorthands: css no, markdown yes
</pre>
<pre class=biblio>
{
"BLUETOOTH42": {
"href": "https://www.bluetooth.org/DocMan/handlers/DownloadDoc.ashx?doc_id=286439",
"title": "BLUETOOTH SPECIFICATION Version 4.2",
"publisher": "Bluetooth SIG",
"date": "2 December 2014"
},
"BLUETOOTH-ASSIGNED": {
"href": "https://www.bluetooth.org/en-us/specification/assigned-numbers",
"title": "Assigned Numbers",
"status": "Living Standard",
"publisher": "Bluetooth SIG"
},
"BLUETOOTH-ASSIGNED-SERVICES": {
"href": "https://developer.bluetooth.org/gatt/services/Pages/ServicesHome.aspx",
"title": "Bluetooth GATT Specifications > Services",
"status": "Living Standard",
"publisher": "Bluetooth SIG"
},
"BLUETOOTH-ASSIGNED-CHARACTERISTICS": {
"href": "https://developer.bluetooth.org/gatt/characteristics/Pages/CharacteristicsHome.aspx",
"title": "Bluetooth GATT Specifications > Characteristics",
"status": "Living Standard",
"publisher": "Bluetooth SIG"
},
"BLUETOOTH-ASSIGNED-DESCRIPTORS": {
"href": "https://developer.bluetooth.org/gatt/descriptors/Pages/DescriptorsHomePage.aspx",
"title": "Bluetooth GATT Specifications > Descriptors",
"status": "Living Standard",
"publisher": "Bluetooth SIG"
},
"BLUETOOTH-SUPPLEMENT6": {
"href": "https://www.bluetooth.org/DocMan/handlers/DownloadDoc.ashx?doc_id=302735",
"title": "Supplement to the Bluetooth Core Specification Version 6",
"date": "14 July 2015",
"publisher": "Bluetooth SIG"
}
}
</pre>
<pre class="anchors">
spec: BLUETOOTH-ASSIGNED
type: enum; urlPrefix: https://developer.bluetooth.org/gatt/
urlPrefix: characteristics/Pages/CharacteristicViewer.aspx?u=org.bluetooth.characteristic.
text: org.bluetooth.characteristic.body_sensor_location; url: body_sensor_location.xml#
text: org.bluetooth.characteristic.gap.appearance; url: gap.appearance.xml#
text: org.bluetooth.characteristic.heart_rate_control_point; url: heart_rate_control_point.xml#
text: org.bluetooth.characteristic.heart_rate_measurement; url: heart_rate_measurement.xml#
text: org.bluetooth.characteristic.ieee_11073-20601_regulatory_certification_data_list; url: ieee_11073-20601_regulatory_certification_data_list.xml#
urlPrefix: descriptors/Pages/DescriptorViewer.aspx?u=org.bluetooth.descriptor.
text: org.bluetooth.descriptor.gatt.characteristic_presentation_format; url: gatt.characteristic_presentation_format.xml#
text: org.bluetooth.descriptor.gatt.client_characteristic_configuration; url: gatt.client_characteristic_configuration.xml#
urlPrefix: services/Pages/ServiceViewer.aspx?u=org.bluetooth.service.
text: org.bluetooth.service.cycling_power; url: cycling_power.xml#
text: org.bluetooth.service.heart_rate; url: heart_rate.xml#
type: dfn
text: Shortened Local Name; url: https://www.bluetooth.org/en-us/specification/assigned-numbers/generic-access-profile#
spec: ECMAScript; urlPrefix: https://tc39.github.io/ecma262/#
type: abstract-op
text: CanonicalNumericIndexString; url: sec-canonicalnumericindexstring
text: CreateDataProperty; url: sec-createdataproperty
text: IsInteger; url: sec-isinteger
type: dfn
text: current realm; url: current-realm
text: fulfilled; url: sec-promise-objects
text: internal slot; url: sec-object-internal-methods-and-internal-slots
text: realm; url: sec-code-realms
type: method
text: Array.prototype.map; url: sec-array.prototype.map
text: [[OwnPropertyKeys]]; for: Object; url: sec-ordinary-object-internal-methods-and-internal-slots-ownpropertykeys
type: interface
text: Array; url: sec-array-objects
text: ArrayBuffer; url: sec-arraybuffer-constructor
text: DataView; url: sec-dataview-constructor
text: Map; url: sec-map-constructor
text: Promise; url:sec-promise-objects
text: Set; url: sec-set-objects
text: TypeError; url: sec-native-error-types-used-in-this-standard-typeerror
text: TypedArray; url: sec-typedarray-constructors
spec: fingerprinting-guidance; urlPrefix: https://w3c.github.io/fingerprinting-guidance/#
type: dfn
text: fingerprinting surface; url: dfn-fingerprinting-surface
spec: WebIDL; urlPrefix: https://heycam.github.io/webidl/#
type: dfn
text: a copy of the bytes held; url: dfn-get-buffer-source-copy
</pre>
<pre class="link-defaults">
spec: fingerprinting-guidance
type: dfn
text: fingerprinting surface
spec: html
type: dfn
text: browsing context; for: /
text: global object; for: /
</pre>
<style>
.argument-list { display: inline-block; vertical-align: top; }
/* Show self-links for various elements. This is incompatible with nearby floats. */
.note, .why, .example, .issue { overflow: inherit; }
.unstable::before {
content: "This section is not stable.";
float: right;
color: red;
}
.unstable {
background-image: url("data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' width='300' height='290'><text transform='rotate(-45)' text-anchor='middle' font-family='sans-serif' font-weight='bold' font-size='70' y='210' opacity='.1'>Unstable</text></svg>");
background-repeat: repeat
}
.unstable.example:not(.no-marker)::before {
content: "Example " counter(example) " (Unstable)";
float: none;
}
.note {
background-color: rgba(145, 235, 145, .2);
}
.example {
background-color: rgba(240, 230, 170, .2);
}
.def {
background-color: rgba(85, 170, 255, .2);
}
.issue {
background-color: rgba(235, 145, 145, .2);
}
</style>
<section>
<h2 id="introduction">Introduction</h2>
<em>This section is non-normative.</em>
<p>
<a href="https://developer.bluetooth.org/">Bluetooth</a> is
a standard for short-range wireless communication between devices.
Bluetooth "Classic" (<abbr title="Basic Rate">BR</abbr>/<abbr title="Enhanced Data Rate">EDR</abbr>)
defines a set of binary protocols and supports speeds up to about 24Mbps.
Bluetooth 4.0 introduced a new "Low Energy" mode known as "Bluetooth Smart",
<abbr title="Bluetooth Low Energy">BLE</abbr>, or just <abbr title="Low Energy">LE</abbr>
which is limited to about 1Mbps but
allows devices to leave their transmitters off most of the time.
BLE provides most of its functionality through key/value pairs provided by
the <a lt="Generic Attribute Profile">Generic Attribute Profile
(<abbr title="Generic Attribute Profile">GATT</abbr>)</a>.
</p>
<p>
BLE defines multiple roles that devices can play.
The <a>Broadcaster</a> and <a>Observer</a> roles are
for transmitter- and receiver-only applications, respectively.
Devices acting in the <a>Peripheral</a> role can receive connections,
and devices acting in the <a>Central</a> role can connect to <a>Peripheral</a> devices.
</p>
<p>
A device acting in either the <a>Peripheral</a> or <a>Central</a> role
can host a <a>GATT Server</a>,
which exposes a hierarchy of <a>Service</a>s, <a>Characteristic</a>s, and <a>Descriptor</a>s.
See [[#information-model]] for more details about this hierarchy.
Despite being designed to support BLE transport,
the GATT protocol can also run over BR/EDR transport.
</p>
<p>
The first version of this specification allows web pages,
running on a UA in the <a>Central</a> role, to connect to <a>GATT Server</a>s
over either a BR/EDR or LE connection.
While this specification cites the [[BLUETOOTH42]] specification,
it intends to also support communication
among devices that only implement Bluetooth 4.0 or 4.1.
</p>
<section>
<h3 id="introduction-examples">Examples</h3>
<div class="example" id="example-heart-rate-monitor">
<p>
To discover and retrieve data from a standard heart rate monitor,
a website would use code like the following:
</p>
<pre highlight="js">
let chosenHeartRateService = null;
navigator.bluetooth.<a idl for="Bluetooth" lt="requestDevice()">requestDevice</a>({
filters: [{
services: ['heart_rate'],
}]
}).then(device => device.gatt.<a for="BluetoothRemoteGATTServer">connect()</a>)
.then(server => server.<a idl for="BluetoothRemoteGATTServer" lt="getPrimaryService()"
>getPrimaryService</a>(<a idl lt="org.bluetooth.service.heart_rate"
>'heart_rate'</a>))
.then(service => {
chosenHeartRateService = service;
return Promise.all([
service.<a idl for="BluetoothRemoteGATTService" lt="getCharacteristic()"
>getCharacteristic</a>(<a idl lt="org.bluetooth.characteristic.body_sensor_location"
>'body_sensor_location'</a>)
.then(handleBodySensorLocationCharacteristic),
service.<a idl for="BluetoothRemoteGATTService" lt="getCharacteristic()"
>getCharacteristic</a>(<a idl lt="org.bluetooth.characteristic.heart_rate_measurement"
>'heart_rate_measurement'</a>)
.then(handleHeartRateMeasurementCharacteristic),
]);
});
function handleBodySensorLocationCharacteristic(characteristic) {
if (characteristic === null) {
console.log("Unknown sensor location.");
return Promise.resolve();
}
return characteristic.<a for="BluetoothRemoteGATTCharacteristic">readValue()</a>
.then(sensorLocationData => {
let sensorLocation = sensorLocationData.getUint8(0);
switch (sensorLocation) {
case 0: return 'Other';
case 1: return 'Chest';
case 2: return 'Wrist';
case 3: return 'Finger';
case 4: return 'Hand';
case 5: return 'Ear Lobe';
case 6: return 'Foot';
default: return 'Unknown';
}
}).then(location => console.log(location));
}
function handleHeartRateMeasurementCharacteristic(characteristic) {
return characteristic.<a for="BluetoothRemoteGATTCharacteristic">startNotifications()</a>
.then(char => {
characteristic.addEventListener('<a event>characteristicvaluechanged</a>',
onHeartRateChanged);
});
}
function onHeartRateChanged(event) {
let characteristic = event.target;
console.log(parseHeartRate(characteristic.<a attribute for="BluetoothRemoteGATTCharacteristic">value</a>));
}
</pre>
<p>
<code>parseHeartRate()</code> would be defined using the
<a idl lt="org.bluetooth.characteristic.heart_rate_measurement"
><code>heart_rate_measurement</code> documentation</a>
to read the {{DataView}} stored
in a {{BluetoothRemoteGATTCharacteristic}}'s
{{BluetoothRemoteGATTCharacteristic/value}} field.
</p>
<pre highlight="js">
function parseHeartRate(data) {
let flags = data.getUint8(0);
let rate16Bits = flags & 0x1;
let result = {};
let index = 1;
if (rate16Bits) {
result.heartRate = data.getUint16(index, /*littleEndian=*/true);
index += 2;
} else {
result.heartRate = data.getUint8(index);
index += 1;
}
let contactDetected = flags & 0x2;
let contactSensorPresent = flags & 0x4;
if (contactSensorPresent) {
result.contactDetected = !!contactDetected;
}
let energyPresent = flags & 0x8;
if (energyPresent) {
result.energyExpended = data.getUint16(index, /*littleEndian=*/true);
index += 2;
}
let rrIntervalPresent = flags & 0x10;
if (rrIntervalPresent) {
let rrIntervals = [];
for (; index + 1 < data.byteLength; index += 2) {
rrIntervals.push(data.getUint16(index, /*littleEndian=*/true));
}
result.rrIntervals = rrIntervals;
}
return result;
}
</pre>
<p>
<code>onHeartRateChanged()</code> might log an object like
</p>
<pre highlight="js">
{
heartRate: 70,
contactDetected: true,
energyExpended: 750, // Meaning 750kJ.
rrIntervals: [890, 870] // Meaning .87s and .85s.
}
</pre>
<p>
If the heart rate sensor reports the <code>energyExpended</code> field,
the web application can reset its value to <code>0</code> by writing to the
{{org.bluetooth.characteristic.heart_rate_control_point|heart_rate_control_point}}
characteristic:
</p>
<pre highlight="js">
function resetEnergyExpended() {
if (!chosenHeartRateService) {
return Promise.reject(new Error('No heart rate sensor selected yet.'));
}
return chosenHeartRateService.<a idl for="BluetoothRemoteGATTService" lt="getCharacteristic()"
>getCharacteristic</a>(<a idl lt="org.bluetooth.characteristic.heart_rate_control_point"
>'heart_rate_control_point'</a>)
.then(controlPoint => {
let resetEnergyExpended = new Uint8Array([1]);
return controlPoint.<a idl for="BluetoothRemoteGATTCharacteristic" lt="writeValue()">writeValue</a>(resetEnergyExpended);
});
}
</pre>
</div>
</section>
</section>
<section>
<h2 id="security-and-privacy">Security and privacy considerations</h2>
<section>
<h3 id="device-access-is-powerful">Device access is powerful</h3>
<p>
When a website requests access to devices using
{{Bluetooth/requestDevice()}},
it gets the ability to access all GATT services mentioned in the call.
The UA MUST inform the user what capabilities these services give the website
before asking which devices to entrust to it.
If any services in the list aren't known to the UA,
the UA MUST assume they give the site complete control over the device
and inform the user of this risk.
The UA MUST also allow the user to inspect what sites have access to what devices
and <a lt="revoke Bluetooth access">revoke</a> these pairings.
<p>
The UA MUST NOT allow the user to pair entire classes of devices with a website.
It is possible to construct a class of devices
for which each individual device sends the same Bluetooth-level identifying information.
UAs are not required to attempt to detect this sort of forgery
and MAY let a user pair this pseudo-device with a website.
<p>
To help ensure that only the entity the user approved for access actually has access,
this specification requires that only <a>secure context</a>s
can access Bluetooth devices
(<a idl lt="Bluetooth">requestDevice</a>).
</p>
</section>
<section class="non-normative">
<h3 id="server-takeovers">Trusted servers can serve malicious code</h3>
<em>This section is non-normative.</em>
<p>
Even if the user trusts an origin,
that origin's servers or developers could be compromised,
or the origin's site could be vulnerable to XSS attacks.
Either could lead to users granting malicious code access to valuable devices.
Origins should define a Content Security Policy ([[CSP3]])
to reduce the risk of XSS attacks,
but this doesn't help with compromised servers or developers.
</p>
<p>
The ability to retrieve granted devices after a page reload,
provided by <a href="#permission-api-integration"></a>,
makes this risk worse.
Instead of having to get the user to grant access while the site is compromised,
the attacker can take advantage of previously-granted devices
if the user simply visits while the site is compromised.
On the other hand, when sites can keep access to devices across page reloads,
they don't have to show as many permission prompts overall,
making it more likely that users will pay attention to the prompts they do see.
</p>
</section>
<section>
<h3 id="attacks-on-devices">Attacks on devices</h3>
<em>This section is non-normative.</em>
<p>
Communication from websites can break the security model of some devices,
which assume they only receive messages from
the trusted operating system of a remote device.
Human Interface Devices are a prominent example,
where allowing a website to communicate would allow that site to log keystrokes.
This specification includes a <a>GATT blocklist</a> of
such vulnerable services, characteristics, and descriptors
to prevent websites from taking advantage of them.
</p>
<p>
We expect that many devices are vulnerable to unexpected data delivered to their radio.
In the past, these devices had to be exploited one-by-one,
but this API makes it plausible to conduct large-scale attacks.
This specification takes several approaches to make such attacks more difficult:
<ul>
<li>
Pairing individual devices instead of device classes
requires at least a user action before a device can be exploited.
<li>
Constraining access to <a>GATT</a>, as opposed to generic byte-stream access,
denies malicious websites access to most parsers on the device.
<p>
On the other hand,
GATT's <a>Characteristic</a> and <a>Descriptor</a> values are still byte arrays,
which may be set to lengths and formats the device doesn't expect.
UAs are encouraged to validate these values when they can.
<li>
This API never exposes Bluetooth addressing, data signing or encryption keys
(<a>Definition of Keys and Values</a>) to websites.
This makes it more difficult for a website to predict the bits that will be sent over the radio,
which blocks <a href="https://www.usenix.org/legacy/events/woot11/tech/final_files/Goodspeed.pdf">packet-in-packet injection attacks</a>.
Unfortunately, this only works over encrypted links,
which not all BLE devices are required to support.
</li>
</ul>
<p>
UAs can also take further steps to protect their users:
<ul>
<li>
A web service may collect lists of malicious websites and vulnerable devices.
UAs can deny malicious websites access to any device
and any website access to vulnerable devices.
</ul>
</section>
<section>
<h3 id="bluetooth-device-identifiers">Bluetooth device identifiers</h3>
<em>This section is non-normative.</em>
<p>
Each Bluetooth BR/EDR device has a unique 48-bit MAC address
known as the <a>BD_ADDR</a>.
Each Bluetooth LE device has at least one of a <a>Public Device Address</a>
and a <a>Static Device Address</a>.
The <a>Public Device Address</a> is a MAC address.
The <a>Static Device Address</a> may be regenerated on each restart.
A BR/EDR/LE device will use the same value
for the <a>BD_ADDR</a> and the <a>Public Device Address</a>
(specified in the <a>Read BD_ADDR Command</a>).
</p>
<p>
An LE device may also have a unique, 128-bit <a>Identity Resolving Key</a>,
which is sent to trusted devices during the bonding process.
To avoid leaking a persistent identifier, an LE device may scan and advertise using
a random Resolvable or Non-Resolvable <a>Private Address</a>
instead of its Static or Public Address.
These are regenerated periodically (approximately every 15 minutes),
but a bonded device can check whether one of its stored <a>IRK</a>s matches
any given Resolvable Private Address
using the <a>Resolvable Private Address Resolution Procedure</a>.
</p>
<p>
Each Bluetooth device also has a human-readable <a>Bluetooth Device Name</a>.
These aren't guaranteed to be unique, but may well be, depending on the device type.
<section>
<h4 id="remote-device-identifiers">Identifiers for remote Bluetooth devices</h4>
<em>This section is non-normative.</em>
<p>
If a website can retrieve any of the persistent device IDs,
these can be used, in combination with a large effort to catalog ambient devices,
to discover a user's location.
A device ID can also be used to identify that a user who
pairs two different websites with the same Bluetooth device
is a single user.
On the other hand, many GATT services are available
that could be used to fingerprint a device,
and a device can easily expose a custom GATT service to make this easier.
</p>
<p>
This specification <a href="#note-device-id-tracking">suggests</a> that
the UA use different device IDs for a single device
when its user doesn't intend scripts to learn that it's a single device,
which makes it difficult for websites to abuse the device address like this.
Device makers can still design their devices to help track users,
but it takes work.
</p>
</section>
<section>
<h4 id="ua-bluetooth-address">The UA's Bluetooth address</h4>
<em>This section is non-normative.</em>
<p>
In BR/EDR mode, or in LE mode during active scanning without the <a>Privacy Feature</a>,
the UA broadcasts its persistent ID to any nearby Bluetooth radio.
This makes it easy to scatter hostile devices in an area and track the UA.
As of 2014-08, few or no platforms document that they implement the <a>Privacy Feature</a>,
so despite this spec recommending it, few UAs are likely to use it.
This spec does <a href="#requestDevice-user-gesture">require a user gesture</a>
for a website to trigger a scan, which reduces the frequency of scans some,
but it would still be better for more platforms to expose the <a>Privacy Feature</a>.
</section>
</section>
<section class="non-normative">
<h3 id="availability-fingerprint">Exposing Bluetooth availability</h3>
<em>This section is non-normative.</em>
<p>
<code>navigator.bluetooth.{{getAvailability()}}</code>
exposes whether a Bluetooth radio is available on the user's system.
Some users might consider this private,
although it's hard to imagine the damage that would result from revealing it.
This information also increases the UA's <a>fingerprinting surface</a> by a bit.
This function returns a {{Promise}},
so UAs have the option of asking the user what value they want to return,
but we expect the increased risk to be small enough that
UAs will choose not to prompt.
</p>
</section>
</section>
<section>
<h2 id="device-discovery" oldids="requestDevice-secure-context">Device Discovery</h2>
<pre class="idl">
dictionary BluetoothDataFilterInit {
BufferSource dataPrefix;
BufferSource mask;
};
dictionary BluetoothLEScanFilterInit {
sequence<BluetoothServiceUUID> services;
DOMString name;
DOMString namePrefix;
// Maps unsigned shorts to BluetoothDataFilters.
object manufacturerData;
// Maps BluetoothServiceUUIDs to BluetoothDataFilters.
object serviceData;
};
dictionary RequestDeviceOptions {
sequence<BluetoothLEScanFilterInit> filters;
sequence<BluetoothServiceUUID> optionalServices = [];
boolean acceptAllDevices = false;
};
interface Bluetooth : EventTarget {
[SecureContext]
Promise<boolean> getAvailability();
[SecureContext]
attribute EventHandler onavailabilitychanged;
[SecureContext, SameObject]
readonly attribute BluetoothDevice? referringDevice;
[SecureContext]
Promise<BluetoothDevice> requestDevice(optional RequestDeviceOptions options);
};
Bluetooth implements BluetoothDeviceEventHandlers;
Bluetooth implements CharacteristicEventHandlers;
Bluetooth implements ServiceEventHandlers;
</pre>
<div class="note" heading="{{Bluetooth}} members">
<p>
{{Bluetooth/getAvailability()}} informs the page
whether Bluetooth is available at all.
An adapter that's disabled through software should count as available.
Changes in availability,
for example when the user physically attaches or detaches an adapter,
are reported through the {{availabilitychanged}} event.
</p>
<p class="unstable">
{{Bluetooth/referringDevice}} gives access to
the device from which the user opened this page, if any.
For example, an <a href="https://developers.google.com/beacons/eddystone">Eddystone</a> beacon
might advertise a URL, which the UA allows the user to open.
A {{BluetoothDevice}} representing the beacon would be available
through <code>navigator.bluetooth.{{referringDevice}}</code>.
</p>
<p>
{{Bluetooth/requestDevice(options)}} asks the user
to grant this origin access to a device
that <a>matches any filter</a> in <code>options.<dfn dict-member for="RequestDeviceOptions">filters</dfn></code>.
To <a>match a filter</a>, the device has to:
</p>
<ul>
<li>
support <em>all</em> the GATT service UUIDs
in the <dfn dict-member for="BluetoothLEScanFilterInit">services</dfn> list
if that member is present,
</li>
<li>
have a name equal to <dfn dict-member for="BluetoothLEScanFilterInit">name</dfn>
if that member is present,
</li>
<li>
have a name starting with <dfn dict-member for="BluetoothLEScanFilterInit">namePrefix</dfn>
if that member is present,
</li>
<li class="unstable">
advertise <a>manufacturer specific data</a> matching all of the key/value pairs in
<dfn dict-member for="BluetoothLEScanFilterInit">manufacturerData</dfn>
if that member is present, and
</li>
<li class="unstable">
advertise <a>service data</a> matching all of the key/value pairs in
<dfn dict-member for="BluetoothLEScanFilterInit">serviceData</dfn>
if that member is present.
</li>
</ul>
<p link-for-hint="BluetoothDataFilterInit" class="unstable">
Both <a>Manufacturer Specific Data</a> and <a>Service Data</a>
map a key to an array of bytes.
{{BluetoothDataFilterInit}} filters these arrays.
An array matches if it has a |prefix| such that
<code>|prefix| & {{mask}}</code> is equal to <code>{{dataPrefix}} & {{mask}}</code>.
</p>
<p>
Note that
if a device changes its behavior significantly when it connects,
for example by not advertising its identifying manufacturer data anymore
and instead having the client discover some identifying GATT services,
the website may need to include filters for both behaviors.
</p>
<p>
In rare cases,
a device may not advertise enough distinguishing information
to let a site filter out uninteresting devices.
In those cases, a site can set
<dfn dict-member for="RequestDeviceOptions">acceptAllDevices</dfn> to `true`
and omit all {{RequestDeviceOptions/filters}}.
This puts the burden of selecting the right device entirely on the site's users.
If a site uses {{RequestDeviceOptions/acceptAllDevices}},
it will only be able to use services listed in {{RequestDeviceOptions/optionalServices}}.
</p>
<p>
After the user selects a device to pair with this origin,
the origin is allowed to access any service whose UUID was listed
in the {{BluetoothLEScanFilterInit/services}} list
in any element of <code>options.filters</code>
or in <code>options.<dfn dict-member for="RequestDeviceOptions">optionalServices</dfn></code>.
</p>
<p>
This implies that if developers filter just by name,
they must use {{RequestDeviceOptions/optionalServices}} to get access to any services.
</p>
</div>
<div class="example" id="example-filter-by-services">
<p>
Say the UA is close to the following devices:
</p>
<table class="data">
<thead><th>Device</th><th>Advertised Services</th></thead>
<tr><td>D1</td><td>A, B, C, D</td></tr>
<tr><td>D2</td><td>A, B, E</td></tr>
<tr><td>D3</td><td>C, D</td></tr>
<tr><td>D4</td><td>E</td></tr>
<tr><td>D5</td><td><i><none></i></td></tr>
</table>
<p>
If the website calls
</p>
<pre highlight="js">
navigator.bluetooth.requestDevice({
filters: [ {services: [A, B]} ]
});
</pre>
<p>
the user will be shown a dialog containing devices D1 and D2.
If the user selects D1, the website will not be able to access services C or D.
If the user selects D2, the website will not be able to access service E.
</p>
<p>
On the other hand, if the website calls
</p>
<pre highlight="js">
navigator.bluetooth.requestDevice({
filters: [
{services: [A, B]},
{services: [C, D]}
]
});
</pre>
<p>
the dialog will contain devices D1, D2, and D3,
and if the user selects D1,
the website will be able to access services A, B, C, and D.
</p>
<p>
The <code>optionalServices</code> list doesn't add any devices
to the dialog the user sees,
but it does affect which services the website can use from the device the user picks.
</p>
<pre highlight="js">
navigator.bluetooth.requestDevice({
filters: [ {services: [A, B]} ],
optionalServices: \[E]
});
</pre>
<p>
Shows a dialog containing D1 and D2,
but not D4, since D4 doesn't contain the required services.
If the user selects D2, unlike in the first example,
the website will be able to access services A, B, and E.
</p>
<p>
The allowed services also apply if the device changes after the user grants access.
For example, if the user selects D1 in the previous <code>requestDevice()</code> call,
and D1 later adds a new E service,
that will fire the {{serviceadded}} event,
and the web page will be able to access service E.
</p>
</div>
<div class="example" id="example-filter-by-name">
<p>
Say the devices in the <a href="#example-filter-by-services">previous example</a>
also advertise names as follows:
</p>
<table class="data">
<thead><th>Device</th><th>Advertised Device Name</th></thead>
<tr><td>D1</td><td>First De…</td></tr>
<tr><td>D2</td><td><i><none></i></td></tr>
<tr><td>D3</td><td>Device Third</td></tr>
<tr><td>D4</td><td>Device Fourth</td></tr>
<tr><td>D5</td><td>Unique Name</td></tr>
</table>
<p>
The following table shows which devices the user can select between
for several values of <var>filters</var> passed to
<code>navigator.bluetooth.requestDevice({filters: <var>filters</var>})</code>.
</p>
<table class="data">
<thead><th><var>filters</var></th><th>Devices</th><th>Notes</th></thead>
<tr>
<td>
<pre highlight="js">
[{name: "Unique Name"}]
</pre>
</td>
<td>D5</td>
<td></td>
</tr>
<tr>
<td>
<pre highlight="js">
[{namePrefix: "Device"}]
</pre>
</td>
<td>D3, D4</td>
<td></td>
</tr>
<tr>
<td>
<pre highlight="js">
[{name: "First De"},
{name: "First Device"}]
</pre>
</td>
<td><i><none></i></td>
<td>
D1 only advertises a prefix of its name,
so trying to match its whole name fails.
</td>
</tr>
<tr>
<td>
<pre highlight="js">
[{namePrefix: "First"},
{name: "Unique Name"}]
</pre>
</td>
<td>D1, D5</td>
<td></td>
</tr>
<tr>
<td>
<pre highlight="js">
[{services: \[C],
namePrefix: "Device"},
{name: "Unique Name"}]
</pre>
</td>
<td>D3, D5</td>
<td></td>
</tr>
</table>
</div>
<div class="example unstable" id="example-filter-by-manufacturer-service-data">
<p>
Say the devices in the <a href="#example-filter-by-services">previous example</a>
also advertise manufacturer or service data as follows:
</p>
<table class="data">
<thead><th>Device</th><th>Manufacturer Data</th><th>Service Data</th></thead>
<tr><td>D1</td><td>17: 01 02 03</td><td></td></tr>
<tr><td>D2</td><td></td><td>A: 01 02 03</td></tr>
</table>
<p>
The following table shows which devices the user can select between
for several values of <var>filters</var> passed to
<code>navigator.bluetooth.requestDevice({filters: <var>filters</var>})</code>.
</p>
<table class="data">
<thead><th><var>filters</var></th><th>Devices</th></thead>
<tr>
<td>
<pre highlight="js">
[{manufacturerData: {17: {}}}]
</pre>
</td>
<td>D1</td>
</tr>
<tr>
<td>
<pre highlight="js">
[{serviceData: {"A": {}}}]
</pre>
</td>
<td>D2</td>
</tr>
<tr>
<td>
<pre highlight="js">
[{manufacturerData: {17: {}}},
{serviceData: {"A": {}}}]
</pre>
</td>
<td>D1, D2</td>
</tr>
<tr>
<td>
<pre highlight="js">
[{manufacturerData: {17: {}},
serviceData: {"A": {}}}]
</pre>
</td>
<td><i><none></i></td>
</tr>
<tr>
<td>
<pre highlight="js">
[{manufacturerData: {
17: {dataPrefix: new Uint8Array([1, 2, 3])},
}}]
</pre>
</td>
<td>D1</td>
</tr>
<tr>
<td>
<pre highlight="js">
[{manufacturerData: {
17: {dataPrefix: new Uint8Array([1, 2, 3, 4])},
}}]
</pre>
</td>
<td><i><none></i></td>
</tr>
<tr>
<td>
<pre highlight="js">
[{manufacturerData: {
17: {dataPrefix: new Uint8Array([1])},
}}]
</pre>
</td>
<td>D1</td>
</tr>
<tr>
<td>
<pre highlight="js">
[{manufacturerData: {
17: {dataPrefix: new Uint8Array([0x91, 0xAA]),
mask: new Uint8Array([0x0F, 0x57])},
}}]
</pre>
</td>
<td>D1</td>
</tr>
<tr>
<td>
<pre highlight="js">
[{manufacturerData: {
17: {},
18: {},
}}]
</pre>
</td>
<td><i><none></i></td>
</tr>
</table>
</div>
<div class="example" id="example-disallowed-filters"
link-for-hint="RequestDeviceOptions">
<p>
Filters that either accept or reject all possible devices cause {{TypeError}}s.
To accept all devices, use {{acceptAllDevices}} instead.
</p>
<table class="data">
<thead><th>Call</th><th>Notes</th></thead>
<tr>
<td>
<pre highlight="js">
requestDevice({})
</pre>
</td>
<td>Invalid: An absent list of filters doesn't accept any devices.</td>
</tr>
<tr>
<td>
<pre highlight="js">
requestDevice({filters:[]})
</pre>
</td>
<td>Invalid: An empty list of filters doesn't accept any devices.</td>
</tr>
<tr>
<td>
<pre highlight="js">
requestDevice({filters:[{}]})
</pre>
</td>
<td>Invalid: An empty filter accepts all devices, and so isn't allowed either.</td>
</tr>
<tr>
<td>
<pre highlight="js">
requestDevice({
acceptAllDevices:true
})
</pre>
</td>
<td>
Valid: Explicitly accept all devices with {{acceptAllDevices}}.
</td>
</tr>
<tr>
<td>
<pre highlight="js">
requestDevice({
filters: [...],
acceptAllDevices:true
})
</pre>
</td>
<td>Invalid: {{acceptAllDevices}} would override any {{filters}}.</td>
</tr>
<tr>
<td>
<pre highlight="js">
requestDevice({
filters:[{namePrefix: ""}]
})
</pre>