How to clear the Firefox cache on a Mac

Clear the cache from Firefox's settings

1. In the menu bar at the top of the screen, click Firefox and choose Settings (on some versions it says Preferences).
2. Select the Privacy and security panel.
3. In the Browsing data section, click Clear browsing data.
4. Next to When:, choose Everything, and make sure only Temporary cached files and pages is ticked.
5. Click Clear, then close the Settings page. Changes there save themselves.

Leaving the other boxes unticked is what keeps you signed in to sites. Mozilla gives a second route to the same dialog: click the menu button, choose History, then Clear Recent History…, and tick the same single item.

Clear it every time Firefox closes

1. Open Firefox → Settings and select Privacy and security, then go to the History section.
2. Choose Customize history, and click Choose what you want Firefox to remember to open the advanced settings.
3. Tick Clear history when Firefox closes, then click Settings….
4. Tick Temporary cached files and pages, untick anything you want to keep, and click Save Changes.

Every quit then empties the cache, and pages load a little slower the first time after each start, while Firefox fetches them again.

Where the cache is on the Mac

Firefox keeps your profile, with your bookmarks, passwords, cookies and history, in ~/Library/Application Support/Firefox/Profiles. The cache is not in there. It sits in a separate folder under ~/Library/Caches/Firefox/Profiles, one per profile, with the cache itself in a folder called cache2. To confirm the exact path on your Mac, type about:cache in Firefox's address bar: the disk section names the folder. To see how much it holds:

du -sh ~/Library/Caches/Firefox 2>/dev/null

If you would rather clear it in Finder, quit Firefox first, press Shift-Command-G, go to ~/Library/Caches/Firefox/Profiles, open your profile's folder and drag cache2 to the Trash, then empty the Trash. Leave the folder in Application Support alone: that is your profile, not a cache, and deleting it loses your bookmarks and saved passwords. Firefox's own setting above does the same job without the risk, and is the one to use.

Why it comes back

The cache holds images, scripts and other parts of sites you visit so they load faster the next time. It refills as you browse, so clearing it is worth doing when a site misbehaves or the disk is short, and it is not a lasting saving. For the other caches on a Mac, Safari's and Chrome's included, see how to clear the cache on a Mac.

Where the app comes in

RefreshYourMac has no Firefox category of its own. Firefox's cache folder is in ~/Library/Caches, so it is measured and cleared with everything else there under Application Caches, rated Safe for auto removal. Quit Firefox first for the best result. It does not touch your Firefox profile in Application Support. Application Caches is in both editions; in the Mac App Store edition it is included once you allow the Caches folder in Settings → Folders. For everything else worth checking, see how to free up space on a Mac.