The temporary Internet files in Firefox, sometimes called the cache, are the copies of text, images, and other data from recently viewed websites that are stored on your hard drive.
As far as troubleshooting a problem goes, deleting temporary Internet files is helpful when a web page won't load but you're pretty confident that the site works.
Deleting the temporary Internet files in Firefox is safe, and you can choose options to ensure that stored features like cookies and passwords won't be removed.
Follow the easy steps below to clear the cache in Firefox:
1. Open Firefox.
2. Go to the right corner of the top toolbar, and click the “Open menu” icon, which is in the
shape of three horizontal bars.
3. A dialog box will open. Select History.
4. The History screen will open. Select Clear Recent History...
5. The Clear Recent History dialog box will open. Choose the time range you’d like for
clearing data, e.g., “Last Hour,” “Everything,” etc.
6. Click the chevron in front of “Details.” A dropdown menu will appear. Uncheck all options
except “Cache” then click Clear Now.