Plugin Support in Firefox 52

Last year, Mozilla announced that support for NPAPI plugins (except for Flash) would be ending in March 2017. That date is approaching fast, so I wanted to give folks more information about what’s happening. If you subscribe to my newsletter, this is the same information I gave there.

In short, Firefox 51 (which was released last week) is the last release of mainline Firefox that will support NPAPI plugins (except for Flash). Starting with Firefox 52, the only version of Firefox that will support plugins is the ESR. Firefox 52 WILL NOT have plugin support (except for Flash). Firefox 52 ESR WILL have plugin support.

That means that if your users are currently on Firefox 51 and you need plugin support, you need to switch Firefox so that it gets updates from the ESR channel. To do this, you need to change two files, channel-prefs.js and update-settings.ini.

In defaults/prefs/channel-prefs.js, change:

pref("", "release");


pref("", "esr");

In update-settings.ini, change:




It is important that you make this change as close as possible to the release of Firefox 52 ESR (March 7, 2017), otherwise security updates to Firefox 51 will not be applied.

Plugin support will continue in the 52 ESR line only, meaning Firefox 59 will not have plugin support.

Some folks may ask why both Mozilla didn’t wait until Firefox 53 to deprecate plugins so that both versions of Firefox 52 would have the same capabilities. If they had done that, users who needed plugins would have had to downgrade to Firefox 52 ESR and that could cause incompatibilities with profiles. It made more sense to encourage people to switch to the same version (52 to 52 ESR).

Please note: I reserve the right to delete comments that are offensive or off-topic.

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20 thoughts on “Plugin Support in Firefox 52

    • No, they have not, but 59 ESR is to be assumed.

      Note that Firefox is the last modern browser to even have plugin support.

  1. The last time I checked, you could add the plugin.load_flash_only preference to Firefox 52 and then turn it off. So if you need to get someone back running with plugins quickly, you can set that, and then get them moved over to ESR before 53 comes out, when non-Flash NPAPI support is really dropped.

    • That should also give you the option of pre-emptively setting the pref in Firefox 51, so you don’t have to time the switchover to 52 ESR so carefully.

    • The reason I didn’t recommend this method is because it would require installing Firefox 52 over Firefox 52 ESR which is more painful than just allowing Firefox 51 to update to Firefox 52 ESR.

      But you can certainly do it that way.

  2. It would’ve been nice if removal of ALSA support in Firefox 52 got the same deal. Slacko Puppy is allergic to PulseAudio and this PC is too ancient to be capable of compiling Fx with the necessary flag to enable ALSA so it forces me to change distros sooner because 52 ESR is also dropping ALSA.

  3. Hi,
    How can I find those files in Mac OS X? I would imagine this could/should be done in about:config but I can find nothing similar to:


    I did find the “” to be changed to “esr”

  4. All IP Cams worldwide using RTSP for online streaming until now were watched in browser by VLC Web Plugin in Firefox or IE. Now only IE is possible. Thousand of webapps and pages will be affected by this change.