For years, Mozilla has aimed to make the Web plug-in-free by enhancing Web standard technologies because plug-ins are negatively affecting the browser performance, security and user experience.

From animation effects, video playback, drag & drop file upload, clipboard manipulation to interactive 3D games, realtime video chat, now everything can be done without a plug-in. Firefox offers a build-in PDF reader and DRM support as well.

Microsoft has deprecated Silverlight. Oracle has also announced the deprecation of the Java browser plug-in in January 2016. As of April 2016, QuickTime for Windows is no longer supported by Apple. The QuickTime plug-in for OS X has already been disabled since 10.9 Mavericks. Unity 5.4 shipped in July 2016 removed the support for the Unity Web Player plug-in.

Therefore, the legacy NPAPI plug-in support in Firefox, deprecated since October 2015, has been removed from Firefox 52 with the exception of still-popular Adobe Flash Player. On the Windows 64-bit version of Firefox, Flash and Silverlight are already the only supported plug-ins. Web publishers must develop a plan to replace any plug-in content, including Java applets and Silverlight videos, with alternative technologies.

For enterprise users who require Java in particular, Firefox 52 Extended Support Release (ESR) will keep the plug-in support enabled until May 2018.