Performance and connectivity

Deal with error messages, crashing applications, connectivity issues, and slow performance.

In English

Secure connection and security warning error pages in Firefox

Server Not Found - Troubleshoot connection problems

Captive portal detection

Fix "The bookmarks and history system will not be functional" error message

Connection settings in Firefox

Troubleshoot time-related errors on secure websites

Fix error “Website will not allow Firefox to display the page.”

Use Troubleshoot Mode in Firefox

Troubleshoot security error codes on secure websites

Troubleshoot and diagnose Firefox problems

Resist Fingerprinting

Fix Firefox using too much memory or CPU resources

Task Manager - see whether tabs or extensions are slowing down Firefox

Warning Unresponsive script - What it means and how to fix it

Crash reports in Firefox for Android

Firefox can't load websites but other browsers can

Firefox hangs or is not responding - How to fix

Firefox DNS over HTTPS

Troubleshoot Mode Thunderbird

Disable Firefox Sync

How can I tell if Mozilla VPN is connected?

Use the Troubleshooting Information page to help fix Firefox issues

Joining public WiFi while on Mozilla VPN

Unsent crash reports in Firefox

Unload inactive tabs to save system memory in Firefox

How Thunderbird for Android avoids leaking your IP address to SMTP servers

Websites look wrong or appear differently than they should

Rebuilding the Global Database

Where to go for developer support

What do the security warning codes mean?

What is the Mozilla VPN kill switch?

Troubleshoot Mozilla VPN connection problems

How to fix the Update Failed error message when updating Firefox

How to reset the default user agent on Firefox

DNS over HTTPS (DoH) FAQs

Connecting to unsecured networks while using Mozilla VPN

Firefox blocked by macOS 15 Sequoia firewall - What you need to know

Crash reports in Firefox for iOS

How to let Firefox use the internet on your Windows computer

Certificate contains the same serial number as another certificate

Quick fixes if your Firefox slows down

"Firefox is already running but is not responding" error - How to fix

Thunderbird makes unrequested connections

Some videos won't play in background

How do I report a broken site in Firefox desktop?

Identify problems caused by third-party modules in Firefox for Windows

How to enable Always-on VPN on Android

How do I report an issue with Firefox Relay?

Mozilla Crash Reporter TB

Rate your Firefox experience, surveys and out of date messages (Heartbeat)

Drag and Drop errors with Firefox Launcher Process enabled and Windows UAC disabled - How to Fix

Report Site Issues on Firefox for iOS

Compacting folders - Potential complications

Troubleshooting speed issues on Mozilla VPN

Where can I get help with the MDN API and documentation?

HTTPS-First upgrades to secure connections

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

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

64-bit Firefox crashes with Citrix's XenApp VM

How to obtain the Mozilla VPN Logs

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

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?

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

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