Server-sent events

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Server-Sent Events (SSE) is a server push technology enabling a client to receive automatic updates from a server via an HTTP connection, and describes how servers can initiate data transmission towards clients once an initial client connection has been established. They are 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. The Server-Sent Events EventSource API is standardized as part of HTML5[1] by the W3C.


The WHATWG Web Applications 1.0 proposal[2] 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".[3][4]

Browser support

Web browser support for Server-Sent Events
Browser Supported Notes
Internet Explorer No [5]
Mozilla Firefox Yes Starting with Firefox 6 [5]
Google Chrome Yes Starting with Chrome 6 [5]
Opera Yes Starting with Opera 11.5 [5]
Safari Yes Starting with Safari 5.0 [5]
Microsoft Edge Yes Starting with Edge 79 [5]



  • Service Stack EventSource library with both server and client implementations.


  • SignalR - Transparent implementation for ASP.NET.


  • HaSSEs Asynchronous server-side SSE daemon written in C (It uses one thread for all connected clients).


  • Lasse EventSource server handler for Erlang's cowboy
  • Shotgun EventSource client in Erlang



  • jEaSSE - Server-side asynchronous implementation for Java servlets and Vert.x
  • Akka HTTP has SSE support since version 10.0.8
  • alpakka Event Source Connector EventSource library for alpakka which supports reconnection
  • Spring WebFlux Server and client side Java implementation built on reactive streams and non-blocking servers
  • Jersey has a full implementation of JAX-RS support for Server Sent Events as defined in JSR-370
  • Micronaut HTTP server supports emitting Server Sent Events
  • JeSSE - Server-side library with user/session management, group broadcast, and authentication
  • Armeria has server and client-side asynchronous SSE implementation built on top of Netty and Reactive Streams
  • Play Framework Event Source for server-sent event emission


  • sse-stream - Node.js/Browserify implementation (client and server).
  • total.js - web application framework for Node.js - example + supports WebSockets (RFC 6455)
  • eventsource-node - EventSource client for Node.js
  • Thread-SSE - A library for Node.js and web browser to develop security and high-performance SSE.

Objective C

  • TRVSEventSource - EventSource implementation in Objective-C for iOS and macOS using NSURLSession.





  • Faye - Simple pub/sub messaging for the web.


  • Warp A super-easy, composable, web server framework for warp speeds.



  • EventSource - EventSource implementation using NSURLSession.

See also

  • Chunked transfer encoding
  • Push technology
  • Comet


  1. ^ "Server-Sent Events". W3C. 17 July 2013.
  2. ^ "Web Applications 1.0 specification".
  3. ^ "Event Streaming to Web Browsers".
  4. ^ Stream Updates with Server-Sent Events, Eric Bidelman, HTML5Rocks website.
  5. ^ a b c d e f When can I use... Server-sent DOM events

External links

Edited: 2021-06-18 14:12:22