Performance and connectivity Deal with error messages, crashing applications, connectivity issues, and slow performance. In English Server Not Found - Troubleshoot connection problems Secure connection and security warning error pages in Firefox Troubleshoot time-related errors on secure websites Fix "The bookmarks and history system will not be functional" error message Captive portal detection Fix error “Website will not allow Firefox to display the page.” Use Troubleshoot Mode in Firefox Troubleshoot and diagnose Firefox problems Troubleshoot security error codes on secure websites Fix Firefox using too much memory or CPU resources Crash reports in Firefox for Android How can I tell if Mozilla VPN is connected? Task Manager - see whether tabs or extensions are slowing down Firefox Resist Fingerprinting Unsent crash reports in Firefox How do I report a broken site in Firefox desktop? Troubleshoot Mode Thunderbird Connection settings in Firefox Warning Unresponsive script - What it means and how to fix it Rebuilding the Global Database What do the security warning codes mean? How Thunderbird for Android avoids leaking your IP address to SMTP servers Firefox DNS over HTTPS DNS over HTTPS (DoH) FAQs How to let Firefox use the internet on your Windows computer What is the Mozilla VPN kill switch? Joining public WiFi while on Mozilla VPN Unload inactive tabs to save system memory in Firefox How to fix the Update Failed error message when updating Firefox Use the Troubleshooting Information page to help fix Firefox issues Quick fixes if your Firefox slows down How to reset the default user agent on Firefox Connecting to unsecured networks while using Mozilla VPN "Firefox is already running but is not responding" error - How to fix Mozilla Crash Reporter TB Where to go for developer support How do I report an issue with Firefox Relay? Crash reports in Firefox for iOS Firefox hangs or is not responding - How to fix Thunderbird makes unrequested connections Rate your Firefox experience, surveys and out of date messages (Heartbeat) How to obtain the Mozilla VPN Logs How to enable Always-on VPN on Android Firefox takes a long time to start up Firefox can't load websites but other browsers can Drag and Drop errors with Firefox Launcher Process enabled and Windows UAC disabled - How to Fix Disable Firefox Sync Report Site Issues on Firefox for iOS Compacting folders - Potential complications Solutions for "Can not create temp folder archive" error when installing Firefox (Windows 10) The language of the websites I visit changes when I turn Mozilla VPN on - What to do How can I help submit and resolve bugs in the MDN content repo? Where can I get help with the MDN API and documentation? Unsent crash reports in Firefox for Android Websites look wrong or appear differently than they should Firefox uses too many CPU resources - How to fix Websites say that Firefox is outdated or incompatible even though it's the latest version Firefox says it's just updated every time it starts - how to fix Certificate contains the same serial number as another certificate Firefox does not work - Common fixes to get you back up and running How can I help by submitting mobile performance data? Memory constraints, Firefox performance and Firewalls Rebuilding Global Database How to resolve weak crypto error messages on Firefox Certificate warnings in Firefox for iOS Some videos won't play in background 64-bit Firefox crashes with Citrix's XenApp VM Profiling Thunderbird Performance Firefox for iOS won't load web pages How to fix an error when trying to open Telegram or Slack on Firefox Fritz!box isn't working when Mozilla VPN is on Identify problems caused by third-party modules in Firefox for Windows Troubleshooting speed issues on Mozilla VPN Difficulties opening or using a website in Firefox 100 Difficulties opening or using a website in Firefox Focus for Android 100 How do I contact MDN Plus support? Why do I see a white screen after updating Mozilla VPN to version 2.8.3? Troubleshoot Mozilla VPN connection problems Firefox hangs when copying with Suggested Actions enabled on Windows 11 - What to do X-Mouse Button Control in Firefox 110 RCS messaging and Mozilla VPN Firefox blocked by macOS 15 Sequoia firewall - What you need to know Address screen sharing issues with Firefox on macOS 15 Sequoia HTTPS-First upgrades to secure connections Troubleshoot Firefox crashes (closing or quitting unexpectedly) Firefox is stuck in Troubleshoot Mode Firefox repeatedly opens empty tabs or windows after you click on a link Fix video and audio problems on Firefox for Windows N editions Avoid crashes - Tips and tricks Problems with email and how to find help Firefox keeps crashing at startup Home page with pipe character opens extra tabs when Firefox starts How to run Firefox when your profile is missing or inaccessible