Here are you options for running unsigned add-ons in Firefox

Your favorite Firefox add-on just stopped working in the browser or refuses to install? If that happens to you it could be because of a new policy over at Mozilla that requires add-ons to be signed before they can be installed or activated in the Firefox web browser.

The policy is not live yet -- Mozilla postponed the enforcement part to Firefox 44 which will come out on January 26, 2016 according to the official Firefox release schedule.

Right now, you may receive warnings that unsigned add-ons are run and when Firefox 43 is released, may experience the blocking for the first time.

Mozilla plans to ship Firefox 43 with an override but will remove it again when the browser hits version 44.

Once Firefox 44 has been released, Firefox will only accept signed add-ons on the stable and beta channel.

Error messages

Firefox displays the following error messages in regards to unsigned add-ons.

When you try to install an add-on that is not signed and add-on signing is enforced:

Firefox has prevented this site from installing an unverified add-on.

When you install an unsigned add-on when add-on signing is not enforced:

Caution: This site would like to install an unverified add-on in Firefox. Proceed at your own risk.

When you have an unsigned add-on installed in Firefox and check the add-on manager:

"Add-on name" could not be verified for use in Firefox. Proceed with caution.

When add-on signing is enforced and there is an unsigned add-on installed in Firefox:

"Add-on name" will be disabled after you restart Firefox.

When you start Firefox with add-on signing enforced and an unsigned add-on installed:

"Add-on name" could not be verified for use in Firefox and has been disabled.

Your options

There are options however that may work for you. Lets take a closer look at all of them:

1. Don't upgrade Firefox Stable or Beta so that these browsers never hit version 44. This works obviously but is not recommended as you will miss out on security and stability fixes that Mozilla releases regularly.
2. Use Firefox ESR instead. Mozilla's plans to keep the override in Firefox ESR so that you can override the add-on signing requirement in Firefox ESR and use it instead of Firefox Stable. Note that Mozilla may change this in the future.
3. Use Firefox Developer edition or Nightly. These test versions of Firefox support the override switch so that you can install unsigned add-ons in them once you make the configuration change. Note that these may not be as stable as Beta or Final versions of Firefox.
4. Mozilla announced that it will release unbranded versions of Firefox. It is unclear right now when these will be released and how well they will be supported. The main idea here is to give add-on developers access to Stable and Beta versions of Firefox so that they can test their add-ons without having to go through the signing process each time they make a change during development. Unbranded editions will only be available in the en-US locale.
5. Switch to a Firefox fork or spin-off. Developers of SeaMonkey, Pale Moon, Thunderbird and other programs based on Firefox code have either set outright that they won't support add-on signing at all, won't enforce it or will keep the override switch available. This may change obviously in the future.

The override switch

We have talked about this before but since it is important to have all information at hand from a single resource, I'd like to guide you through enabling the override again here on this page.

1. Type about:config in the Firefox address bar and hit enter.
2. Confirm that you will be careful if a warning page is displayed.
3. Use the search at the top to find xpinstall.signatures.require.
4. Double-click on the preference to toggle its value so that it is set to false.

Doing so allows you to install unsigned extensions in the Firefox web browser. Please note that the override will be removed in Firefox 44 Stable and Beta.

Now You: Do you run unsigned add-ons? If so, what do you plan to do about it?