How to Fix Firefox Slow Performance and High Memory on Windows

What Causes This?

Firefox slowdowns and high memory use usually come from too many open tabs, heavy websites, buggy extensions, or a damaged browser profile. Hardware acceleration, outdated Firefox builds, and background Windows apps can also make Firefox feel sluggish. In some cases, Firefox is not the only problem — low available RAM, startup bloat, or system junk on Windows can make memory spikes worse.

Common Symptoms

• Firefox takes a long time to open or switch tabs
• RAM usage in Task Manager keeps climbing while browsing
• Pages stutter, freeze, or become unresponsive
• Firefox crashes or shows “Not Responding”
• Your whole PC feels slower when Firefox is open

How to Fix It Manually

1. Check how much memory Firefox is using

   • Open Task Manager with Ctrl + Shift + Esc.
   • Click More details if Task Manager opens in compact view.
   • Under the Processes tab, find Firefox and check the Memory column.
   • If Firefox is using a lot of RAM, also look for other apps using memory at the same time.

2. Close unnecessary tabs and restart Firefox

   • Too many tabs, especially video, social media, and web apps, can use a large amount of memory.
   • Save anything important, then close unused tabs.
   • Click the menu button in Firefox (three lines in the top-right) and choose Exit.
   • Reopen Firefox and see if performance improves.

3. Disable or remove problematic extensions

   • In Firefox, press Ctrl + Shift + A to open Add-ons and themes.
   • Click Extensions.
   • Turn off extensions you do not need, especially ad blockers, shopping tools, VPN add-ons, download helpers, and tab managers.
   • Restart Firefox after disabling them.
   • If Firefox becomes faster, re-enable extensions one by one to find the one causing the issue.

4. Turn off hardware acceleration

   • In Firefox, click the menu button > Settings.
   • Scroll to the Performance section.
   • Uncheck Use recommended performance settings.
   • Uncheck Use hardware acceleration when available.
   • Close and reopen Firefox.
   • This helps if Firefox is lagging because of graphics driver issues.

5. Update Firefox

   • Click the menu button > Help > About Firefox.
   • Firefox will automatically check for updates and install them.
   • Click Restart to update Firefox if prompted.
   • Newer versions often fix memory leaks and performance bugs.

6. Test Firefox in Troubleshoot Mode

   • Click the menu button > Help > Troubleshoot Mode.
   • Click Restart, then Open.
   • This temporarily disables extensions and custom settings.
   • If Firefox runs normally in Troubleshoot Mode, the problem is likely caused by an extension, theme, or setting.

7. Reduce Windows background load

   • Open Task Manager with Ctrl + Shift + Esc and review apps using high CPU or Memory.
   • Press Windows + I to open Settings, then go to Apps > Startup.
   • Turn off startup apps you do not need running in the background.
   • Restart your PC to clear memory and apply changes.

Fix It Automatically with Kudu

If you do not want to hunt through Firefox settings and Windows background processes manually, Kudu can help. It scans for performance issues that contribute to browser slowdowns — such as startup bloat, unnecessary background apps, and system clutter — and helps fix them quickly so Firefox has more resources available.

Download Kudu Free →