PSA: Legacy extensions disabled by default on Nightly

Mathieu Pillard mpillard at
Tue Aug 15 00:21:19 UTC 2017

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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