Open Firefox on your computer.
Click the menu button (three lines β°) in the top-right corner.
Select Settings.
In the left-hand menu, go to Privacy & Security.
Scroll down to the Cookies and Site Data section.
Click Clear Data…
You’ll see two checkboxes:
Cookies and Site Data
Cached Web Content
Click Clear.
β Done! Firefox has now removed all cache, cookies, and background data stored by websites.
Open Firefox.
Go to the menu (β°) → Settings.
Select Privacy & Security from the sidebar.
Scroll to the Cookies and Site Data section.
Click Manage Data…
A list of websites that have stored data will appear.
Select the site from the list.
Click Remove Selected, then click Save Changes.
Confirm by clicking Remove when prompted.
β Done! The cache, cookies, and background scripts for that specific site have been deleted.