Most addons found below can be converted using the 'Addon Converter for Seamonkey'.

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Archived Add-ons for Firefox
This is an archive of the Firefox add-on page when it had all add-ons available for every version. The search functionality does not work, so this is more useful if you know the direct URL of the add-on you want to use.

LegacyCollector
Mozilla has removed all “legacy extensions” from their add-ons site in November 2018, leaving many users of older “long term support” versions of the browser, as well as browser forks, dead in the water. This holds a (hopefully complete) collection of the removed extensions as they were available from addons.mozilla.org prior to this purge by the company.

Classic Add-on Archive Extension
This is an add-on that installs into Seamonkey and provides a local database of all available add-ons that can be converted to use with Seamonkey. This catalog contains 93,598 versions of 19,450 Firefox add-ons created by 14,274 developers over the past 15 years using XUL/XPCOM technology.

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Seamonkey Addons
Be sure to check the official Seamonkey Addons page first before converting any extensions for use. They may already be officially available for download. Always choose to 'install anyway' even if it's not listed for your version of Seamonkey as most times they still work without issue.

Thunderbird Addons
Since the mail program included with Seamonkey uses Thunderbird code as it's base nearly all Thunderbird addons work but you'll need to click on 'view other versions' which will tell you which versions work with Seamonkey mail. Both Seamonkey and Thunderbird have recently joined forces.

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