This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
Note: This feature is available in Web Workers.
The WebSocket.extensions read-only property returns the extensions selected by the server. This is currently only the empty string or a list of extensions as negotiated by the connection.
A string.
| Specification |
|---|
| WebSockets> # ref-for-dom-websocket-extensions①> |
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Opera | Safari | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | WebView Android | WebView on iOS | |
extensions |
16 | 12 | 8 | 12.1 | 6 | 18 | 8 | 12.1 | 6 | 1.0 | 4.4 | 6 |
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https://developer.mozilla.org/en-US/docs/Web/API/WebSocket/extensions