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