Some Firefox extensions require access to local storage and/or indexedDB, for instance to store data on the user device Firefox runs on.
These extensions may break if cookies are blocked. Extensions like uBlock Origin, uMatrix, or Stylus use the storage and thus require cookie permissions even if they don't set cookies to work correctly.
While some come with fallbacks built-in to overcome this limitation, it is best to address this head on instead as indexedDB usage is usually the better option to whichever fallback solution is used otherwise.
The easiest way to get to the profile folder is to load about:support, and click on the show folder button on the page that opens.
You can check the storage\default directory of the Firefox profile if extensions use indexedDB. If you have folders starting with moz-extension in there, you have extensions that use it and thus require cookie access. Note that the extensions are listed with their internal UUID and not their name. Note that the UUID is randomly assigned during installation. Means: if you uninstall and reinstall, or use the extension on multiple systems, it is different.
Firefox users have two options to address the issue:
- Allow first party cookies, and clean up cookies regularly or block cookies and storage.
- Keep the deny all setting, but use exceptions to allow extensions that need cookie access to use indexedDB storage to function properly.
Set cookie exceptions for extensions in Firefox
- Load about:debugging in Firefox to get started. The page lists all system add-ons, and all installed extensions of the Firefox browser.
- Locate the browser extension that you want to add exceptions for. You find the internal UUID listed next to extensions that you have installed in the browser. This helps with the identification.
- Click on Manifest URL underneath the extension listing.
- Right-click on the page that opens, and select View Page Info from the context menu.
- Switch to the Permissions tab of the Page Info window.
- Locate Set Cookies in the list of permissions. Remove the checkmark from "use default", and set it to allow instead.
- Repeat the process for any other extension that requires access to cookies.
- Restart Firefox.
Tip: You can manage cookie permissions under Options > Privacy & Security > History > use custom settings for history > Accept cookies from websites, Exceptions. You may use the prompt to add cookie exceptions as well. All that is required is to copy the entire folder name, replace the +++ with ://, add it under "address of website" and set it to allow. (e.g. moz-extension+++23bf26fb-1c8d-40d3-b7c2-798882a0d55c to moz-extension://23bf26fb-1c8d-40d3-b7c2-798882a0d55c)
- CCleaner detects extensions cookies but it makes no difference whether it cleans them or not as they get recreated automatically on the next start of the browser.
The Ghacks user.js file for Firefox blocks cookies by default. Users who apply it and run extensions that require cookies may run into issues afterwards. The article highlighted a method to overcome this without enabling first party cookies globally for all sites and extensions in the browser. (Thank you Pants)