Mozilla said its latest move will offer Firefox users "enhanced security, improved battery life, faster page load, and better browser responsiveness".
Mozilla is working to expunge plugins in general from the web. Last year, it announced it would end support for Netscape Plugin Application Programming Interface (NPAPI) plugins except Flash in March 2017. This is partly why Oracle will kill off its Java browser plugin in September.
Websites that use Flash or Silverlight for video or games should plan for HTML technologies "as soon as possible", Mozilla said. These plugins are increasingly becoming redundant as more capabilities are brought by HTML5, including audio and video playback, streaming capabilities, 2D and 3D graphics, and access to components such as the microphone and camera.
The benefit for website operators to switch to HTML technologies, according to Mozilla, is a far lower crash rate when users access their sites.
In May, Google said Flash in Chrome would be disabled for all websites except the top 10 globally that still rely on Flash Player. That move doesn't affect video on sites such Facebook and YouTube, which have already moved to HTML5. Even Adobe, though committed to still developing Flash Player, is moving toward HTML5.