Server-sent events is a technology for providing push notifications from a server to a browser client in the form of DOM events

DOM Events

DOM events allow event-driven programming languages like JavaScript, JScript, ECMAScript, VBScript and Java to register various event handlers/listeners on the element nodes inside a DOM tree, e.g. HTML, XHTML, XUL and SVG documents....

. The Server-Sent Events EventSource API is now being standardized as part of HTML5 by the W3C

World Wide Web Consortium

The World Wide Web Consortium is the main international standards organization for the World Wide Web .Founded and headed by Tim Berners-Lee, the consortium is made up of member organizations which maintain full-time staff for the purpose of working together in the development of standards for the...

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History

The WHATWG Web Applications 1.0 proposal included a mechanism to push content to the client. On September 1, 2006, the Opera web browser implemented this new experimental technology in a feature called "Server-Sent Events."

Overview

Server-Sent Events (SSE) is a standard describing how servers can initiate data transmission towards clients once an initial client connection has been established. It is commonly used to send message updates or continuous data streams to a browser client and designed to enhance native, cross-browser streaming through a JavaScript API called EventSource, through which a client requests a particular URL in order to receive an event stream.

Web browsers

Web browser support for Server-Sent Events

Browser	Supported	Notes
Internet Explorer Internet Explorer Windows Internet Explorer is a series of graphical web browsers developed by Microsoft and included as part of the Microsoft Windows line of operating systems, starting in 1995. It was first released as part of the add-on package Plus! for Windows 95 that year...
Mozilla Firefox Mozilla Firefox Mozilla Firefox is a free and open source web browser descended from the Mozilla Application Suite and managed by Mozilla Corporation. , Firefox is the second most widely used browser, with approximately 25% of worldwide usage share of web browsers...		Starting with Firefox 6.0
Google Chrome Google Chrome Google Chrome is a web browser developed by Google that uses the WebKit layout engine. It was first released as a beta version for Microsoft Windows on September 2, 2008, and the public stable release was on December 11, 2008. The name is derived from the graphical user interface frame, or...
Opera Opera (web browser) Opera is a web browser and Internet suite developed by Opera Software with over 200 million users worldwide. The browser handles common Internet-related tasks such as displaying web sites, sending and receiving e-mail messages, managing contacts, chatting on IRC, downloading files via BitTorrent,...		Starting with Opera 11
Safari Safari (web browser) Safari is a web browser developed by Apple Inc. and included with the Mac OS X and iOS operating systems. First released as a public beta on January 7, 2003 on the company's Mac OS X operating system, it became Apple's default browser beginning with Mac OS X v10.3 "Panther". Safari is also the...		Starting with Safari 5.0

Libraries

• Cramp - Ruby/EventMachine based server implementation for WebSocket and Server-Sent Events

External links

• HTML5 Server-sent events W3C draft specification
• HTML5 Server-push Technologies, Part 1 Introduction into HTML5 Server-push Technologies. Part 1 covers ServerSent Events
• Using server-sent events Concise example how to use server-sent events on Mozilla Developer Network