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