Performance and connectivity

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

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Secure connection and security warning error pages in Firefox

Troubleshoot time-related errors on secure websites

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

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

Captive portal detection

Connection settings in Firefox

Troubleshoot security error codes on secure websites

Use Troubleshoot Mode in Firefox

Troubleshoot and diagnose Firefox problems

Fix Firefox using too much memory or CPU resources

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

What do the security warning codes mean?

How do I report a broken site in Firefox desktop?

Troubleshoot Mode Thunderbird

Crash reports in Firefox for Android

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

Firefox can't load websites but other browsers can

Use the Troubleshooting Information page to help fix Firefox issues

Firefox DNS over HTTPS

Firefox hangs or is not responding - How to fix

Rebuilding the Global Database

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

Certificate contains the same serial number as another certificate

Where to go for developer support

How to let Firefox use the internet on your Windows computer

DNS over HTTPS (DoH) FAQs

Resist Fingerprinting

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

Quick fixes if your Firefox slows down

Joining public WiFi while on Mozilla VPN

How to enable Always-on VPN on Android

Websites look wrong or appear differently than they should

Firefox says it's just updated every time it starts - how to fix

Unload inactive tabs to save system memory in Firefox

Crash reports in Firefox for iOS

Thunderbird makes unrequested connections

How to reset the default user agent on Firefox

64-bit Firefox crashes with Citrix's XenApp VM

Report Site Issues on Firefox for iOS

Compacting folders - Potential complications

Troubleshoot Mozilla VPN connection problems

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

Firefox takes a long time to start up

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

Rate your Firefox experience, surveys and out of date messages (Heartbeat)

Certificate warnings in Firefox for iOS

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

How to obtain the Mozilla VPN Logs

What is the Mozilla VPN kill switch?

Connecting to unsecured networks while using Mozilla VPN

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

Mozilla Crash Reporter TB

Rebuilding Global Database

How to resolve weak crypto error messages on Firefox

Some videos won't play in background

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

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

Troubleshooting speed issues on Mozilla VPN

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

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