What is dash.js?

dash.js is a JavaScript library that plays video in a web browser using a streaming format called MPEG-DASH. DASH stands for Dynamic Adaptive Streaming over HTTP, and it is a method of delivering video that adjusts quality in real time based on the viewer's internet speed. Rather than downloading an entire video file, the browser requests small chunks, and the player picks the right quality level for each chunk depending on how fast the connection is at that moment. This is the same general approach used by YouTube, Netflix, and most large streaming platforms. The library runs entirely in the browser using standard web APIs for handling media and encrypted content. It is a reference implementation, meaning the Dash Industry Forum produced it to demonstrate correct, spec-compliant behavior for developers building DASH players or testing DASH content. Using it is straightforward. You include the library in a web page with a script tag, create a player object, and point it at an MPD file, which is the manifest format DASH uses to describe the available video streams. A working example showing the minimum required code is included in the README and fits in about ten lines of HTML and JavaScript. The library also supports encrypted video through a standard called Encrypted Media Extensions, which lets browsers play content protected by digital rights management systems without browser plugins. The project is maintained by the Dash Industry Forum, the standards body that oversees the DASH specification. Full documentation, a quickstart guide, and a hosted reference player with sample streams are available on the project's documentation site. The library is released under a BSD license.