Server-Sent Events
SSE effectively provides an efficient form of XHR Streaming, where a device can subscribe for updates from a server.
What are Server-Sent Events?
![](https://images.ctfassets.net/ee3ypdtck0rk/2Fbl5f0IImsfv4pLSPbzFR/607117bdd84e4ef23c4690b98cb47071/protocols-server-side-events__1_.png?w=1280&h=616&q=80&fm=png)
Overview
SSE is a push technology commonly used to send unidirectional message updates or continuous data streams to a browser client. SSE aims to enhance native, cross-browser server-to-client streaming through a JavaScript API called EventSource, standardized as part of HTML5 by the World Wide Web Consortium (W3C).
The Ably SSE and raw HTTP streaming API provides a way to get a realtime stream of events from Ably in circumstances where using a full Ably Realtime client library, or even an MQTT library, is impractical.