Firefox similar to other browsers caches image and web files, and saves cookies (small text file stored on your device with preferences and other data for a specific site) from every website you visit, which helps to improve pages loading speeds when you return to the cached sites.
However, cache data and cookies not always work perfectly, and sometimes this data may prevent websites from loading correctly on Firefox, in which case, clearing the cache and cookies may fix the problem.
How to clear Firefox cache and cookies
To clear cookies and cache data from Firefox, use these steps:
Click the setting (humburger) button on the top-right corner.
Click on Options.
Click on Privacy & Security.
Under the “History” section, click the Clear history button.
On “Time range to clear”, select from the drop-down menu the time range to clear the browsing data. (It’s always recommended to select the “Everything” option).
Under the “History” section, check the Cookies and Cache options.
Clear the any other options that you don’t wish to remove. For instance, Browsing & Download History, Active Logins, Form & Search History, Site Preferences, and Offline Website Data.
Click the Clear now button.
Once you completed the steps, websites will load as they should, but you’ll notice that they will take longer to load than usual. This is expected, and it’s because Mozilla Firefox has to re-cache the data again. As a result of clearing up cookies, you may also need to sign-in again to some of your online services.