The EventSource interface is used to receive server-sent events. It connects to a server over HTTP and receives events in text/event-stream format without closing the connection.


Creates a new EventSource from the given USVString.


This interface also inherits properties from its parent, EventTarget.

Is an EventHandler being called when an error occurs and the error event is dispatched on this object.
Is an EventHandler being called when a message event is received, that is when a message is coming from the source.
Is an EventHandler being called when an open event is received, that is when the connection was just opened.
EventSource.readyState Read only
An unsigned short representing the state of the connection. Possible values are CONNECTING (0), OPEN (1), or CLOSED (2).
EventSource.url Read only
A DOMString representing the URL of the source.


This interface also inherits methods from its parent, EventTarget.

Closes the connection, if any, and sets the readyState attribute to CLOSED. If the connection is already closed, the method does nothing.


Specification Status Comment
WHATWG HTML Living Standard
The definition of 'EventSource' in that specification.
Living Standard  

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
 Basic support 9 6.0 (6.0) ? 11 5
CORS support 26 11.0 (11.0) ? 12 ?
Feature Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support 4.4 ? ? ? ?

See also


© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.

API Interface Reference Server-sent events