1. Open your Firefox browser and type “about:memory” in the URL bar.
  2. In the page that show up, you should see a “Minimize Memory Usage” button. If you hover your mouse over it, you will see a description of what it does. Basically, it will trigger a global garbage collection and flush the various cache.

When it is done cleaning up the memory usage, it will show a message “Memory minimization completed”.

That’s it. Note: You won’t see any effect on a freshly open browser. However, on a browser that have been opened for a long time and has many active tabs, you should see that your Firefox is taking up lesser resources now.