Media Source Extensions

Media Source Extensions (MSE) is a W3C specification that allows JavaScript to send byte streams to media codecs within web browsers that support HTML video and audio. Among other possible uses, this allows the implementation of client-side prefetching and buffering code for streaming media entirely in JavaScript. It is compatible with, but should not be confused with, the Encrypted Media Extensions (EME) specification, and neither requires the use of the other, although many EME implementations are only capable of decrypting media data provided via MSE.

Netflix announced experimental support in June 2014 for the use of MSE playback on the Safari browser on the OS X Yosemite beta release.

YouTube started using MSE in its HTML5 player in September 2013.

Browser support
Media Source Extensions API is widely supported across all modern web browsers, with the only exception being iPhone-family devices (although it is supported on iPadOS). Firefox 37 already had a subset of MSE API available for use with only YouTube in Firefox 37 on Windows Vista or later only, while Mac OS X version had in enabled starting version 38.

Minor browsers

 * Pale Moon from version 27.0, since 22 November 2016.

Players

 * NexPlayer for HTML5 MSE and EME supporting HLS and DASH
 * castLabs PRESTOplay video player for HMTL5 MSE and EME supporting DASH and HLS
 * Akamai Media Player as a contributor to the Dash Industry Forum and DASH.js (DASH IF reference client). AMP includes Dash.js, HLS.js and advanced QUIC protocol playback from Akamai Edge Servers
 * Shaka Player, an open source javascript player library for HTML5 MSE and EME video with DASH and HLS support
 * The Video Player by Comcast Technology Solutions
 * THEOplayer by OpenTelly: HLS and MPEG-DASH player for cross-platform HTML5 support without the need for Flash fallback
 * Viblast Player: HLS and MPEG-DASH player for HTML5 MSE and EME, with Flash fallback
 * bitmovin's bitdash MPEG-DASH player for HTML5 MSE and EME, with Flash fallback
 * dash-js for HTML5 MSE
 * dash.js for HTML5 MSE and EME
 * rx-player for HTML5 MSE and EME (Live and On Demand)
 * hls.js for HTML5 MSE
 * hasplayer.js for HTML5 MSE and EME, supporting DASH, Smooth Streaming and HLS
 * JW Player 7 and later for MPEG-DASH using HTML5 MSE and EME
 * SLDP HTML5 Player supports SLDP via MSE playback
 * Azure Media Player supports MSE, EME, DASH, HLS, Flash, and Silverlight. Streaming URLs are published in an
 * Unreal HTML5 player uses MSE for low latency (sub-second) live playback of streams sent via WebSockets by Unreal Media Server
 * Storm Player uses MSE as one of its delivery modes for ultra-low latency streaming via WebSockets by Storm Streaming Server