Beacon API

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since April 2018.

See full compatibility

The Beacon API is used to send an asynchronous and non-blocking request to a web server. The request does not expect a response. Unlike requests made using XMLHttpRequest or the Fetch API, the browser guarantees to initiate beacon requests before the page is unloaded and to run them to completion.

The main use case for the Beacon API is to send analytics such as client-side events or session data to the server. Historically, websites have used XMLHttpRequest for this, but browsers do not guarantee to send these asynchronous requests in some circumstances (for example, if the page is about to be unloaded). To combat this, websites have resorted to various techniques, such as making the request synchronous, that have a bad effect on responsiveness. Because beacon requests are both asynchronous and guaranteed to be sent, they combine good performance characteristics and reliability.

For more details about the motivation for and usage of this API, see the documentation for the navigator.sendBeacon() method.

Note: This API is not available in Web Workers (not exposed via WorkerNavigator).

Interfaces

This API defines a single method: navigator.sendBeacon().

The method takes two arguments, the URL and the data to send in the request. The data argument is optional and its type may be a string, an ArrayBuffer, a TypedArray, a DataView, a ReadableStream, a Blob, a FormData object, or a URLSearchParams object. If the browser successfully queues the request for delivery, the method returns true; otherwise, it returns false.

Specifications

Specification
Beacon # sendbeacon-method

Browser compatibility

	desktop					mobile							server
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on iOS	Samsung Internet	WebView Android	WebView on iOS	Node.js
`sendBeacon`	Chrome – Full support Chrome 39 (Release date: 2014-11-18) footnote footnote Starting in Chrome 59, this method cannot send a `Blob` whose type is not CORS safelisted. This is a temporary change until a mitigation can be found for the security issues that this creates. For more information, see bug 40087600.	Edge – Full support Edge 14 (Release date: 2016-08-02) footnote Full support	Firefox – Full support Firefox 31 (Release date: 2014-07-22) footnote Full support	Opera – Full support Opera 26 (Release date: 2014-12-03) footnote footnote Starting in Opera 46, this method cannot send a `Blob` whose type is not CORS safelisted. This is a temporary change until a mitigation can be found for the security issues that this creates. For more information, see bug 40087600.	Safari – Full support Safari 11.1 (Release date: 2018-04-12) footnote Full support	Chrome Android – Full support Chrome Android 42 (Release date: 2015-04-15) footnote footnote Starting in Chrome 59, this method cannot send a `Blob` whose type is not CORS safelisted. This is a temporary change until a mitigation can be found for the security issues that this creates. For more information, see bug 40087600.	Firefox for Android – Full support Firefox for Android 31 (Release date: 2014-07-22) footnote Full support	Opera Android – Full support Opera Android 29 (Release date: 2015-04-28) footnote footnote Starting in Chrome 59, this method cannot send a `Blob` whose type is not CORS safelisted. This is a temporary change until a mitigation can be found for the security issues that this creates. For more information, see bug 40087600.	Safari on iOS – Full support Safari on iOS 11.3 (Release date: 2018-03-29) footnote Full support	Samsung Internet – Full support Samsung Internet 4 (Release date: 2016-03-11) footnote footnote Starting in Chrome 59, this method cannot send a `Blob` whose type is not CORS safelisted. This is a temporary change until a mitigation can be found for the security issues that this creates. For more information, see bug 40087600.	WebView Android – Full support WebView Android 40 (Release date: 2015-01-21) footnote footnote Starting in Chrome 59, this method cannot send a `Blob` whose type is not CORS safelisted. This is a temporary change until a mitigation can be found for the security issues that this creates. For more information, see bug 40087600.	WebView on iOS – Full support WebView on iOS 11.3 (Release date: 2018-03-29) footnote Full support	Node.js – No support Node.js footnote No support

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Full support: Full support
No support: No support
: See implementation notes.

Beacon API

Interfaces

Specifications

Browser compatibility

Legend

See also