Performance and connectivity Deal with error messages, crashing applications, connectivity issues, and slow performance. Ní Gẹ̀ẹ́sì 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 Troubleshoot and diagnose Firefox problems Diagnose Firefox issues using Troubleshoot Mode What do the security warning codes mean? Troubleshoot Mode Thunderbird Warning Unresponsive script - What it means and how to fix it Task Manager - see whether tabs or extensions are slowing down Firefox Crash reports in Firefox for Android Firefox uses too much memory or CPU resources - How to fix Firefox can't load websites but other browsers can Resist Fingerprinting Firefox DNS over HTTPS How to enable Always-on VPN on Android Firefox hangs or is not responding - How to fix Unload inactive tabs to save system memory in Firefox Use the Troubleshooting Information page to help fix Firefox issues Rebuilding the Global Database Crash reports in Firefox for iOS Websites look wrong or appear differently than they should Certificate contains the same serial number as another certificate "Firefox is already running but is not responding" error - How to fix How Thunderbird for Android avoids leaking your IP address to SMTP servers How to let Firefox use the internet on your Windows computer Connecting to unsecured networks while using Mozilla VPN How do I report an issue with Firefox Relay? Disable Firefox Sync How can I tell if Mozilla VPN is connected? How to fix the Update Failed error message when updating Firefox Server Not Found - Troubleshoot connection problems Where to go for developer support How to obtain the Mozilla VPN Logs Where can I get help with the MDN API and documentation? X-Mouse Button Control in Firefox 110 HTTPS-First upgrades to secure connections Firefox takes a long time to start up Mozilla Crash Reporter TB How to reset the default user agent on Firefox DNS over HTTPS (DoH) FAQs Compacting folders - Potential complications Firefox blocked by macOS 15 Sequoia firewall - What you need to know 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 Quick fixes if your Firefox slows down Thunderbird makes unrequested connections Certificate warnings in Firefox for iOS What is the Mozilla VPN kill switch? Profiling Thunderbird Performance Firefox for iOS won't load web pages Identify problems caused by third-party modules in Firefox for Windows Troubleshooting speed issues on Mozilla VPN How can I help submit and resolve bugs in the MDN content repo? RCS messaging and Mozilla VPN 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 do I report a broken site in Firefox desktop? Drag and Drop errors with Firefox Launcher Process enabled and Windows UAC disabled - How to Fix Report Site Issues on Firefox for iOS Joining public WiFi while on Mozilla VPN How to fix an error when trying to open Telegram or Slack on Firefox Solutions for "Can not create temp folder archive" error when installing Firefox (Windows 10) 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? 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 Address screen sharing issues with Firefox on macOS 15 Sequoia 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 Fix video and audio problems on Firefox for Windows N editions Firefox keeps crashing at startup 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