The EventSource() constructor returns a newly-created EventSource, which represents a remote resource.


eventSource = new EventSource(url, configuration);


A USVString that represents the location of the remote resource serving the events/messages.
configuration Optional
Provides options to configure the new connection. The possible entries are:
  • withCredentials, defaulting to false, indicating if CORS should be set to include credentials.


var evtSource = new EventSource('sse.php');
var eventList = document.querySelector('ul');

evtSource.onmessage = function(e) {
  var newElement = document.createElement("li");

  newElement.textContent = "message: " +;

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


Specification Status Comment
HTML Living Standard
The definition of 'EventSource()' in that specification.
Living Standard Initial definition

Browser compatibility

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
 Basic support 9 6.0 (6.0) ? 11 5
CORS support (withCredentials) 26 11.0 (11.0) ? 12 ?
Available in shared and dedicated workers[1] (Yes) 53.0 (53.0) ? (Yes) ?
Feature Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support 4.4 6.0 (6.0) ? ? ?
CORS support (withCredentials) ? 11.0 (11.0) ? ? ?
Available in shared and dedicated workers[1] ? 53.0 (53.0) ? ? ?

[1] But not service workers as yet.

See also

Document Tags and Contributors

Contributors to this page: chrisdavidmills, carlos-lopez, zemlanin, teoli
Last updated by: chrisdavidmills,