Hey enda,

You can do this manually by following the steps here: https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems#w_disable-all-extensions

Or you can also try starting Firefox in Safe Mode and then enabling each extension individually.

Hopefully this helps!

If you really mean plugins (Tools > Add-ons > Plugins) and not extensions then see:

• https://support.mozilla.org/kb/Troubleshooting+plugins

You will have to disable all plugins manually because there is no way to disable them otherwise.
Plugins are always enabled by default or can be enabled by deleting the pluginreg.dat file.

Using click-to-play (plugins.click_to_play) to enable plugins on request doesn't work well with some plugins, so it is best not to use it.

• https://wiki.mozilla.org/Opt-in_activation_for_plugins