Firefox's Safe Mode, now called Troubleshoot Mode, starts the browser with extensions and themes disabled, hardware acceleration turned off, and some settings temporarily reset. It is the quickest way to find out whether a problem such as crashes, slow pages, missing menus, or odd behavior is caused by an add-on or setting rather than Firefox itself. This guide shows every way to start it on Windows, Mac, and Linux, what to test once you are in, and how to fix the problem you find.
Quick Answer
Click the menu button (three lines) in the top-right corner, choose Help > Troubleshoot Mode, and click Restart, then Open. If Firefox will not open normally, hold Shift (Windows and Linux) or Option (Mac) while starting it.
What Troubleshoot Mode Does
- Disables all extensions and themes.
- Turns off hardware acceleration.
- Uses default toolbar and button layout.
- Temporarily ignores some custom settings.
These changes are temporary. When you restart Firefox normally, your extensions and settings come back unchanged. Firefox renamed Safe Mode to Troubleshoot Mode in 2021 (Firefox 88), so older guides may still use the old name.
Method 1: From the Menu
- Click the menu button ☰.
- Click Help.
- Click Troubleshoot Mode….
- Click Restart in the confirmation box.
- When Firefox reopens, click Open to continue in Troubleshoot Mode.
Method 2: Keyboard Shortcut at Startup
- Windows and Linux: hold Shift while you click the Firefox shortcut.
- Mac: hold Option while you open Firefox.
Keep holding the key until a window appears asking whether to open Firefox in Troubleshoot Mode, then click Open.
Method 3: From the Troubleshooting Information Page
- Type about:support in the address bar and press Enter.
- Click Troubleshoot Mode… on the right side.
- Click Restart, then Open.
Method 4: Command Line
- Windows: press Windows key + R, type
firefox -safe-mode, and press Enter. - Mac: in Terminal, run
/Applications/Firefox.app/Contents/MacOS/firefox -safe-mode. - Linux: in a terminal, run
firefox -safe-mode.
What to Do Once You Are in Troubleshoot Mode
| Result | Likely cause | Next step |
|---|---|---|
| Problem is gone | An extension, theme, or hardware acceleration | Restart normally and disable extensions one at a time |
| Problem remains | Profile data, settings, or something outside Firefox | Try Refresh Firefox, clear cache, or check security software |
Find the problem extension
- Restart Firefox normally.
- Open ☰ > Add-ons and themes > Extensions.
- Turn off all extensions, then turn them on one at a time, testing after each.
- Remove or update the extension that brings the problem back.
Test hardware acceleration
Go to Settings > General > Performance, uncheck Use recommended performance settings, and uncheck Use hardware acceleration when available. Restart Firefox. If this fixes it, update your graphics driver.
Refresh Firefox (If Troubleshoot Mode Does Not Help)
On about:support, click Refresh Firefox. This creates a fresh profile while keeping bookmarks, history, passwords, cookies, and open windows. Extensions and customizations are removed. Your old profile data is saved to an "Old Firefox Data" folder on the desktop.
How to Exit Troubleshoot Mode
Close Firefox completely and open it again normally. Everything returns to how it was.
Frequently Asked Questions
Where is Safe Mode in Firefox?
It is now called Troubleshoot Mode, under ☰ > Help > Troubleshoot Mode.
Will Troubleshoot Mode delete my data?
No. Bookmarks, passwords, and history are not affected, and extensions are only disabled temporarily.
Why does Firefox keep starting in Troubleshoot Mode?
You may be holding Shift or Option by accident, or a shortcut includes the -safe-mode option. Check the shortcut's properties.
Summary
- Go to ☰ > Help > Troubleshoot Mode and click Restart.
- Or hold Shift (Windows) or Option (Mac) while opening Firefox.
- If the problem disappears, check extensions and hardware acceleration.
- If not, try Refresh Firefox from about:support.
Kermit Matthews is a freelance writer based in Philadelphia, Pennsylvania with more than a decade of experience writing technology guides. He has a Bachelor’s and Master’s degree in Computer Science and has spent much of his professional career in IT management.
He specializes in writing content about iPhones, Android devices, Microsoft Office, and many other popular applications and devices.