To provide guidance for site authors and users that continue to rely on Flash, Mozilla has updated its published roadmap for Flash in Firefox. Starting next month, users will choose which websites are able to run the Flash plugin. Flash will be disabled by default for most users in 2019, and only users running the Firefox Extended Support Release (ESR) will be able to continue using Flash through the final end-of-life at the end of 2020. In order to preserve user security, once Flash is no longer supported by Adobe security patches, no version of Firefox will load the plugin.
Starting with Firefox 56 in September 2017, Firefox for Android will remove all support for plugins.
In the second half of 2018, Firefox will no longer remember the Flash setting, and users will have to choose each session whether to activate Flash.
In early 2019, Firefox will show a user-visible warning on sites that continue to use Flash.
A few months after the user-visible warning, Firefox will disable the Flash plugin by default. Users will not be prompted to enable Flash, but it will still be possible to activate Flash on certain sites using browser settings.
In early 2020, Flash support will be completely removed from consumer versions of Firefox. The Firefox Extended Support Release (ESR) will continue to support for Flash until the end of 2020.
When Adobe stops shipping security updates for Flash at the end of 2020, Firefox will refuse to load the plugin.