Signing your add-ons
Starting with Firefox 43, add-on extensions and multi-item add-ons that include extensions need to be signed by Mozilla before they can install in release and beta versions of Firefox. This includes themes and language packs; dictionaries don't need to be signed however.
Unsigned extensions can be installed in Developer Edition, Nightly, and ESR versions of Firefox, after toggling the
xpinstall.signatures.required preference in
Mozilla signs add-ons through the AMO website and provides three methods for submitting your add-on for signing:
All the signing options are subject to the Firefox Add-on Distribution Agreement.
Using the signing API or web-ext returns you signed add-ons, with no distribution listing created on AMO. If you take the option to upload your add-on through the AMO Developer Hub, you're given a choice between listing on AMO or self-distribution. If you choose self-distribution, at the end of the process you download signed copies of your add-on.
Regardless of the method used all add-ons must pass an automated validation before they are signed. They may also be subject to a manual code review. The review criteria applied to add-ons are found in the Add-on Policies.