How to move Firefox legacy extensions to another browser

Mozilla Firefox 57 will be released today; we have reviewed the new version of the web browser yesterday already. The new version comes with light and shadow; light, because it is faster and more responsive across the board, and shadow, because it dropped the old add-on system which Mozilla now calls legacy extensions.

All classic Firefox add-ons that are not WebExtensions at the time when you update to Firefox 57 are disabled automatically, and moved to the "new" legacy extensions section on about:addons.

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While there is a chance that some may get updated to be compatible with Firefox's new extensions system, some won't.

That's bad if you rely on these extensions, and don't or can't use the browser without them. We published a guide on running legacy extensions once Firefox 57 comes along already.

As far as support for legacy extensions is concerned, here is a short table that highlights the situation:

As far as support for legacy extensions is concerned, here is a short table that highlights the situation:

- Firefox 57 or newer -- Does not support legacy extensions. Nightly supports a switch for now, but many extensions don't work if you enable it.
- Firefox ESR 52.* -- The extended support release supports legacy extensions. It will do so until mid-2018 when the version of Firefox is upgraded to version 59.
- Third-party browsers compatible with Firefox -- Pale Moon, Waterfox and SeaMonkey can run legacy extensions. In fact, some can only run legacy extensions and not WebExtensions.

Your options

Your two main options are to install Firefox ESR and use it for the time being, or use a third-party Firefox compatible browser instead.

You can run Firefox and a browser mentioned as an option above side by side. While this may not be practicable in the long run, it may help out some users.

Firefox ESR

Start by downloading a copy of Firefox ESR from the official website. Note that you should not simply run the browser on your system as it picks up the default Firefox profile by default.

You don't want Firefox ESR to use the same profile as other versions of Firefox. This means that you need to create a new profile for the browser and use it exclusively for it.

Tip: Check out our overview of Firefox command line parameters for additional information.

Here is how that is done:

1. Select "custom" during installation, and make sure to select a custom directory for the ESR files.
2. Uncheck the "launch Firefox now" option on the last installation screen and select Finish.
3. Go to the installation directory afterwards and locate the firefox.exe file in it.
4. You need to create a shortcut that points to the file now.
5. On Windows, you'd right-click on firefox.exe and select "Create shortcut" from the context menu.
6. Windows may not be able to create the shortcut in the folder. If that is the case, it suggests to create it on the desktop. Accept that.
7. Right-click on the shortcut that you have created and select properties from the menu again.
8. Locate the "target" field and append -no-remote -p to it. Make sure there is a space between the path and the new parameters, e.g. "C:\Program Files\Mozilla Firefox ESR\firefox.exe" -no-remote -p
9. Close the window afterwards, and run the shortcut.

Firefox will launch the profile manager. Select "create profile" there and follow the profile creation wizard. I suggest you pick a descriptive name, e.g. Firefox ESR, to distinguish it from other Firefox profiles.

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Once you have created the profile, run Firefox ESR using it. Close the browser afterwards again. You can make things a bit easier now that you have created the profile:

1. Right-click on the Firefox shortcut again and select properties.
2, Append "profilename" to the command. Doing so will load the new profile automatically on start, so that the profile manager is not displayed anymore. Example: "C:\Program Files\Mozilla Firefox ESR\firefox.exe" -no-remote -p "FirefoxESR"

Moving legacy extensions

You have two options when it comes to installing legacy extensions in the new Firefox ESR installation. You can either do it manually, or use Firefox Sync for it.

Firefox Sync

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If you don't use Firefox Sync yet, it may be your best option. Since you can also sync preferences, bookmarks and passwords, it is ideal if you need to move these as well to the new installation.

1. In Firefox ESR, load about:preferences#sync and create a new Sync account (or sign in to an existing one).
2. Select what you want to sync afterwards, e.g. only extensions, or other data as well.
3. Start the other Firefox installation and configure Sync there as well. You can run these side by side on the same device thanks to the "no-remote" parameter.

The Firefox ESR version will receive any compatible browser extension afterwards. This includes legacy extensions. Note that it may not accept hybrid extensions such as NoScript.

You may need to install older versions of those extensions manually, as you cannot install these in Firefox ESR at the time.

Manual

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You have two options here: install the extensions from the Firefox profile folder of the regular Firefox installation, or download and install them from Mozilla AMO instead.

Note: Both methods won't install any customizations that you have made.

1. In the regular Firefox version, type about:support and click on the open folder button when the page opens. This opens the Firefox profile that is used in the default file browser on the operating system.
2. Open the extensions folder. Firefox lists all installed extensions in it.
3, Open Firefox ESR, and load about:addons.
4. Select the cogwheel icon and then "install add-on from file".
5. Open the profile location of the regular Firefox version, and pick one of the extension files there.
6. If you have difficulties identifying extensions, consult the extensions section on about:support and compare the IDs there with the file names.

You can go to Mozilla AMO alternatively and download extensions from there.

Third-party Firefox-compatible browsers

You may use Pale Moon or Waterfox instead if you don't want to use Firefox ESR. One reason for not wanting to use Firefox ESR is that it is only a temporary solution.

You don't need to create a separate profile for these, as they use their own profile folder.

There is no direct option however to import extensions to either browser. This leaves you with the manual options describes above.