Troubleshooting
- Unable to scroll with arrow keys
- Unable to uninstall add-ons (extensions or themes)
- Unable to use profile when you launch an older version of Thunderbird
- Unblocking the Java plugin
- Unexpected installation error -203 when installing add-ons
- Uninstall BitGuard to fix crashes with Firefox
- Uninstall BitGuard to fix crashes with Firefox 25
- Uninstalling toolbars
- Unsafe properties of OpenPGP keys might be ignored
- Update Accuweather or Wikipedia
- Update for Accuweather or Wikipedia won't download on ZTE Open
- Updates reported when running newest version
- Updating processor microcode
- Use Internet Explorer messages upon Firefox startup
- Use MDN offline with your MDN Plus subscription
- userChrome.css and .js and userContent are unsupported
- Username and password not remembered
- Usernames and passwords are not saved
- Use the Troubleshooting Information page to help fix Firefox issues
- Using a dedicated profile for Firefox Nightly
- Using OpenPGP secret keys that advertise features that are not supported by Thunderbird
- Using the RealPlayer plugin with Firefox
- Using the Troubleshooting Information page
- Video or audio does not play
- View articles recommended by Pocket on your Firefox for Desktop homepage
- Vine and other HTML5 videos won't play
- Warning Unresponsive plugin - What it means and how to fix it
- Warning Unresponsive script
- Warning Unresponsive script - What it means and how to fix it
- Webpages are large and blurry after updating Firefox - how to fix
- Web pages aren't displaying properly in Firefox for Android
- Website colors are wrong
- Websites don't load - troubleshoot and fix error messages
- Websites incorrectly report that Firefox is outdated or incompatible
- Websites look wrong
- Websites look wrong or appear differently than they should
- Websites or add-ons incorrectly report incompatible browser
- Websites say cookies are blocked
- Websites say cookies are blocked - Unblock them
- Websites say that Firefox is outdated or incompatible even though it's the latest version
- Websites show a spinning wheel and never finish loading
- Website will not allow Firefox to display the page if another site has embedded it
- What does "Your connection is not secure" mean?
- What do the security warning codes mean?
- What happened to Adaptive Search?
- What happened to Firefox Home?
- What happened to the Thunderbird File, Edit, and View menus?
- What is Mozilla BadgeKit?
- What is the difference between Firefox Marketplace and Adaptive App Search?
- What is the different between Firefox Marketplace and Adaptive App Search?
- What is the winmail.dat attachment?
- What should I do if I'm redirected to the Firefox Relay FAQ when clicking a link within an email?
- What's new in Firefox for iOS (version 39)
- What's new in Firefox Klar for Android
- What's new in Firefox Klar for Android (version 93)
- What's new in Firefox Klar for iOS (version 106)
- What's new in Firefox Klar for iOS (version 107)
- What's new in Firefox Klar for iOS (version 40)
- What’s New with Colorways?
- What's the difference between MDN and MDN Plus?
- What to do if Firefox won't play any sounds
- What to do if you can't download or save files
- What to do when searches take you to the wrong search website
- Where can I go for technical help?
- Why aren’t my add-ons working on some websites?
- Why are some add-ons not allowed on sites restricted by Mozilla?
- Why can't Firefox for mobile play Flash on my device?
- Why can't I create a custom ringtone?
- Why can't I sync my passwords?
- Why can’t I use Firefox sync with my Google or Apple ID?
- Why does Monitor show me in a data breach for a site I never signed up to?
- Why does Mozilla disable some add-ons from running in Firefox?
- Why does Thunderbird warn me that my server doesn't use encryption?
- Why does Thunderbird warn me that my server don't use encryption?
- Why do I have to click to activate plugins?
- Why do I have two versions of Firefox in my Windows Control Panel?
- Why do I not see all my hotmail emails on my Firefox OS device?
- Why do I see a message asking if I want to see the page hosted on HTTPS?
- Why do I see a white screen after updating Mozilla VPN to version 2.8.3?
- Why do Java, Silverlight, Adobe Acrobat and other plugins no longer work?
- Why has my "Send" button been replaced with "Send Later"
- Why is each open Firefox tab showing up in the Windows volume mixer?
- Why is each open Firefox tab showing up in the Windows volume mixer? Redirect 1
- Why is Firefox for Mobile slow?
- Will Firefox version 100 work on Windows 7?
- Will policies I set work if users already installed Firefox?
- Windows 10 S won't let me install Firefox
- Windows 10 warns me to use a "Microsoft-verified" app
- Windows in S mode won't let me install Firefox
- Windows Media or other plugins stopped working after Firefox update
- Windows SSO
- Workaround to make Estonian Smartcards work in Firefox 76
- Workaround to make Estonian Smartcards work in Firefox 76+
- Wrong home page opens when I start Firefox - How to fix
- X-Mouse Button Control in Firefox 110
- Yahoo! and at&t mail say your browser is blocking Flash
- Youtube HTML5 does not work in Firefox
- YouTube Thumbnails not loading