Use Older Firefox Extensions Through Classic Add-ons Archive

Last few years have seen dramatic changes in the Firefox browser development – Quantum was released, WebExtensions API was adopted and options are no longer shown in a separate window. By switching to the new form of creating the browser add-ons (WebExtensions API), Firefox basically killed off thousands of the browser extensions that were developed in the past 15 years. Some developers were so annoyed by this move that they completely gave up the development of the extensions (for example, an excellent download manager, DownThemAll extension was abandoned by its developer).

Starting from version 57.0 (when Quantum was first introduced), Firefox no longer allows you to install the older add-ons. Now you can install the newer extensions only that are developed using the WebExtensions API. As of now, the older extensions are available from the Mozilla website, but in the future they will be removed from there. Older extensions are no longer available from Mozilla website.

Firefox add-ons developer with a nickname JustOff has decided to take the matters in his own hands and created an add-on that catalogues thousands of the older add-ons. The add-on for the catalogue is called Classic Add-ons Archive. You can install it in Palemoon, WaterFox and Firefox (versions 56.0 and below).

How do I Install Classic Add-ons Archive?

  1. Download the latest version of XPI file from the Github web page of Classic Add-ons Archive
  2. Launch Palemoon (or Watefox or Firefox) browser.
  3. Drag-n-drop the downloaded XPI file on the Palemoon browser window. Alternatively, you can also press Ctrl+O and select the XPI file.
  4. The familiar add-on installation window will appear. Click on the Install Now button to proceed with the installation.Classic Add-ons Archive
  5. After the installation is finished, it places an icon in the toolbar, clicking upon which you get to browse and install all the classic add-ons as if you are using the Mozilla Add-ons website.

Classic Add-ons Archive

You can also enter caa:list in the address bar to view the Classic Add-ons Archive instead of clicking on the icon. The add-on is nearly 40 MB in size but packs only the catalog and not the actual add-ons. According to the developer, the add-on files are hosted on the cloud through the help of WaterFox development team. It contains thousands of add-ons that were developed between 2004 (when Firefox 1.0 was released) and 2018. The developer JustOff keeps updating and expanding the database from time to time.

For using this Classic Add-ons Archive, you have to install Palemoon (, WaterFox ( or older versions of Firefox (

You can download Classic Add-ons Archive from


  1. I have FF 56, downloaded 2.0.1 xpi from

    I get a message from FF saying that the add-on could installed because it could not be verified. However, in FF I have already changed “xpinstall.signatures.required” to “false” in about:config – so I don’t understand why I am getting this message. Any Ideas?? Thanks..

  2. ** The address wasn’t understood

    Waterfox doesn’t know how to open this address, because one of the following protocols (caa) isn’t associated with any program or is not allowed in this context.

    You might need to install other software to open this address. **

  3. Unfortunately, even the earliest version of ca-archive on the github page won’t install on my Firefox 27.0.1.

    Off to try the other one someone mentioned – thanks.

  4. I’m getting the FF extension can’t be verified error/warning on install. Tried ver 1.2.3 and the newest 2.0.1.

    No joy, any ideas?

    Using FF ver 56.0.2

      1. Well, been meaning to try Waterfox especially since the FF extension Armageddon incident. Guess I’ll have to make the time investment to install and setup with extensive group of add-ons utilized over nearly two decades!

        In the meantime located another archive. Not as extensive as the CAA sounds but useful nonetheless…

  5. we love you thanks for the info just abandoned firefox cos the now suk bigtime and installed waterfox instead heaps better gr8 add ons

  6. This is very nice. I have downloaded and unzipped the package onto disk. HOW DO i INSTALL IT INTO WATERFOX? I don’t see any instructions, even inside the archive.

    1. Just extract the XPI file to a folder. It is named something like ca-archive-1.2.2.xpi. Then drag-n-drop it on Watefox (or Palemoon) window. Alternatively, you can also press Ctrl+O and then select ca-archive-1.2.2.xpi. It will show the usual add-on install window, then proceed with installation.

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