EventSource: readyState property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.

Note: This feature is available in Web Workers.

The readyState read-only property of the EventSource interface returns a number representing the state of the connection.

Value

A number which is one of the three possible state constants defined on the EventSource interface:

EventSource.CONNECTING (0)

The connection is not yet open.

EventSource.OPEN (1)

The connection is open and ready to communicate.

EventSource.CLOSED (2)

The connection is closed or couldn't be opened.

Examples

js
const evtSource = new EventSource("sse.php");
console.log(evtSource.readyState);

Note: You can find a full example on GitHub — see Simple SSE demo using PHP.

Specifications

Specification
HTML
# dom-eventsource-readystate-dev

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobileserver
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
Deno
readyState

Legend

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Full support
Full support

See also