Firefox leaves extension files behind even after you delete the browser

When you uninstall Firefox, the browser program itself disappears, but the extensions you installed remain stored on your computer. These leftover files take up disk space and can cause problems if you reinstall Firefox later — your old extensions may reappear automatically, or conflicting data might slow down the fresh installation. Removing them requires finding the folder where Firefox keeps extension data, which is hidden by default on most systems.

The steps differ slightly depending on whether you use Windows, Mac, or Linux, but the principle is the same: you navigate to Firefox's profile folder and delete the extensions folder inside it. This is a safe operation — you are only removing data files, not system files.

Key Takeaways

  • Firefox stores extension files in a hidden profile folder that remains on your computer even after you uninstall the browser.
  • On Windows, this folder is located at C:\Users\[Your Username]\AppData\Roaming\Mozilla\Firefox\Profiles, and you must enable viewing hidden files first.
  • On Mac, the profile folder is at ~/Library/Application Support/Firefox/Profiles, which you can reach by holding Option and clicking Go in Finder.
  • Deleting the extensions folder inside your Firefox profile removes all extension data permanently and does not affect other Firefox settings.
  • If you want to keep some settings but remove only extensions, you can delete individual extension folders instead of the entire extensions directory.

Finding the Firefox profile folder on Windows

On Windows, Firefox profile data lives in a hidden folder that does not appear in normal file browsing. You must first turn on the option to view hidden files, then navigate to the correct location.

Open File Explorer and click the View tab at the top. Look for a checkbox labeled Hidden items and click it to turn it on. Now hidden folders will appear throughout your file system. Navigate to C:\Users, then open the folder with your username, then open AppData. If AppData does not appear, make sure the Hidden items checkbox is still checked. Inside AppData, open Roaming, then Mozilla, then Firefox, then Profiles. You should see one or more folders with names like abc123de.default-release — these are your Firefox profiles.

Finding the Firefox profile folder on Mac

On Mac, the Firefox profile folder is inside the Library folder, which is hidden by default. The fastest way to reach it is through Finder's Go menu.

Open Finder and click the Go menu at the top. Hold down the Option key on your keyboard — this reveals a Library option that normally stays hidden. Click Library. Navigate to Application Support, then Firefox, then Profiles. You will see one or more profile folders with names like abc123de.default-release.

Deleting the extensions folder

Once you have located your Firefox Profiles folder, open any profile folder inside it. You will see several items, including a folder called extensions. This folder contains all the extension data from your old Firefox installation.

Right-click the extensions folder and select Delete (or press Delete on your keyboard). On Mac, you may see a confirmation dialog asking if you want to move it to Trash — click Move to Trash. The extensions folder and all its contents will be removed. If you want to be thorough, you can also delete the extensions.json file in the same profile folder, which is a record of all extensions Firefox knew about.

If you have multiple profiles, repeat this step for each one. Most people have only one profile, usually named something like default-release.

Removing individual extensions instead of all of them

If you want to keep some extensions but remove others, you can delete specific extension folders instead of the entire extensions directory. Open the extensions folder and look inside — you will see subfolders with long alphanumeric names, each representing one installed extension.

The folder names are not human-readable, so identifying which extension is which is difficult. A better approach is to open the extensions.json file with a text editor like Notepad (Windows) or TextEdit (Mac). This file lists each extension by name. Find the extension you want to remove, note its ID number, then go back to the extensions folder and delete the subfolder matching that ID. This method takes longer but gives you precise control.

What happens after you delete the extensions folder

Once you have removed the extensions folder, those files are gone permanently. If you reinstall Firefox, it will start fresh with no extensions — you will not see your old extensions reappear automatically. Any settings, bookmarks, or passwords you saved in Firefox remain untouched, because they are stored in separate files within the profile folder.

If you later decide you want an extension back, you can reinstall it from the Firefox Add-ons website. Reinstalling does not restore your old settings for that extension, so if you had customized an extension's options, you will need to set them up again.

Cleaning up Firefox data on Linux

On Linux, the Firefox profile folder is located at ~/.mozilla/firefox/ in your home directory. The tilde (~) represents your home folder. Open a file manager and navigate there, or use the terminal command cd ~/.mozilla/firefox/ to jump directly to the location. From there, the process is identical to Windows and Mac — open your profile folder and delete the extensions folder inside it.

If you prefer the command line, you can delete the extensions folder with the command rm -r ~/.mozilla/firefox/[profile-name]/extensions, replacing [profile-name] with the actual name of your profile folder. Be careful with this command, as it deletes immediately without asking for confirmation.

Frequently Asked Questions

Will deleting the extensions folder affect my Firefox bookmarks or passwords?

No. Bookmarks, passwords, and browser history are stored in separate files within the Firefox profile folder. Deleting only the extensions folder leaves all of those intact. If you want to preserve everything when you reinstall Firefox, you can back up the entire profile folder before uninstalling.

What if I cannot find the Firefox Profiles folder?

Make sure you have enabled viewing hidden files. On Windows, check that the Hidden items checkbox in the View tab is turned on. On Mac, confirm you used the Option key when clicking the Go menu in Finder. If you still cannot find it, try typing the full path directly into your file manager's address bar instead of navigating folder by folder.

Can I delete the extensions folder while Firefox is still running?

You should close Firefox completely before deleting the extensions folder. If Firefox is running, it may be actively using those files, and deleting them could cause errors or prevent Firefox from closing properly. Close the browser first, then delete the folder, then reinstall Firefox if you want a fresh start.

Do I need to delete the extensions folder if I am just updating Firefox to a newer version?

No. Updating Firefox keeps your profile folder and all its contents intact, including extensions. You only need to delete the extensions folder if you are completely uninstalling Firefox and want to remove all traces of your old extensions before reinstalling.

What is the extensions.json file, and should I delete it too?

The extensions.json file is a record that Firefox maintains of all extensions it knows about. Deleting it is optional — Firefox will recreate it the next time it runs. Deleting both the extensions folder and the extensions.json file ensures a completely clean slate, but deleting just the extensions folder is usually sufficient.