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 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 Mozilla Crash Reporter TB Diagnose Firefox issues using Troubleshoot Mode What do the security warning codes mean? Troubleshoot and diagnose Firefox problems Warning Unresponsive script - What it means and how to fix it Task Manager - see whether tabs or extensions are slowing down Firefox Firefox uses too much memory or CPU resources - How to fix Resist Fingerprinting Troubleshoot Mode Thunderbird Where to go for developer support DNS over HTTPS (DoH) FAQs How to fix the Update Failed error message when updating Firefox Rebuilding the Global Database How to reset the default user agent on Firefox How to let Firefox use the internet on your Windows computer Certificate contains the same serial number as another certificate Firefox hangs or is not responding - How to fix Use the Troubleshooting Information page to help fix Firefox issues How do I report a broken site in Firefox desktop? Firefox DNS over HTTPS Mozilla VPN won’t connect or keeps disconnecting - How to fix "Firefox is already running but is not responding" error - How to fix How can I tell if Mozilla VPN is connected? Firefox blocked by macOS 15 Sequoia firewall - What you need to know Thunderbird makes unrequested connections Crash reports in Firefox for iOS Websites look wrong or appear differently than they should Firefox can't load websites but other browsers can What is the Mozilla VPN kill switch? Unload inactive tabs to save system memory in Firefox How to enable Always-on VPN on Android Where can I get help with the MDN API and documentation? Retrieve a Pocket crash log on Android Server Not Found - Troubleshoot connection problems Drag and Drop errors with Firefox Launcher Process enabled and Windows UAC disabled - How to Fix Connecting to unsecured networks while using Mozilla VPN Identify problems caused by third-party modules in Firefox for Windows Troubleshooting speed issues on Mozilla VPN How to find the Pocket app crash logs on iOS Firefox takes a long time to start up Firefox says it's just updated every time it starts - how to fix Quick fixes if your Firefox slows down Certificate warnings in Firefox for iOS Report Site Issues on Firefox for iOS Joining public WiFi while on Mozilla VPN The language of the websites I visit changes when I turn Mozilla VPN on - What to do Firefox hangs when copying with Suggested Actions enabled on Windows 11 - What to do How do I report an issue with Firefox Relay? X-Mouse Button Control in Firefox 110 RCS messaging and Mozilla VPN HTTPS-First upgrades to secure connections 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 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 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 Disable Firefox Sync How to obtain the Mozilla VPN Logs Crash reports in Firefox for Android 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 Compacting folders - Potential complications Solutions for "Can not create temp folder archive" error when installing Firefox (Windows 10) Fritz!box isn't working when Mozilla VPN is on 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? Why do I see a white screen after updating Mozilla VPN to version 2.8.3? 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 Problems with email and how to find help Avoid crashes - Tips and tricks 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