PSA: Legacy extensions disabled by default on Nightly

Kevin Jones kevinhowjones at
Tue Aug 15 00:36:13 UTC 2017

Thanks for that clarification, Matthieu.

I suppose then what a Nightly user would need to do in order to update a
legacy addon (say the dev did a critical bug fix) would be to uninstall the
addon first so it would appear in the "Available Add-ons" search (I have
observed installed addons no longer appear in that search) then hopefully
find it and install it.

On Mon, Aug 14, 2017 at 6:21 PM, Mathieu Pillard <mpillard at>

> On 15/08/2017 01:58, Kevin Jones wrote:
> No.  If you can get a link to the addon, it will install it.  And it will
> run as long as `extensions.legacy.enabled` is true.
> Like Mathieu replied on this thread (In order to get the install button
> active):
> "One workaround for this is to set "extensions.checkCompatibility.nightly"
> to false in about:config. This will force nightly to ask AMO to ignore
> compatibility information when updating extensions. Do this at your own
> risk though, ignoring compatibility usually leads to broken add-ons."
> My reply about that pref was only valid in the context of updates of
> already installed add-ons. When using the website, AMO can't access any of
> those prefs and doesn't let you install incompatible add-ons - that
> includes legacy ones in Firefox 57.
> If you want to *install* and not just update legacy extensions, you have
> to go through the Add-on Manager search functionality (Tools -> Add-ons ->
> Extensions -> Search all add-ons), which uses AMO APIs but presents the
> results within Firefox itself, honoring those prefs. Note that the special
> API used by the add-on manager has several limitations, so search results
> might differ from what you see on the website (in particular, it won't show
> you add-ons marked as experimental by their author(s)). Again, do this at
> your own risk.
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