Performance and connectivity

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

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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

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

Mozilla Crash Reporter TB

Troubleshoot and diagnose Firefox problems

Diagnose Firefox issues using Troubleshoot Mode

What do the security warning codes mean?

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

Firefox uses too much memory or CPU resources - How to fix

Resist Fingerprinting

Troubleshoot Mode Thunderbird

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

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

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

How to fix the Update Failed error message when updating Firefox

DNS over HTTPS (DoH) FAQs

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

Firefox hangs or is not responding - How to fix

Firefox can't load websites but other browsers can

How to reset the default user agent on Firefox

How do I report a broken site in Firefox desktop?

Firefox DNS over HTTPS

Unload inactive tabs to save system memory in Firefox

Where to go for developer support

Crash reports in Firefox for Android

How can I tell if Mozilla VPN is connected?

Certificate contains the same serial number as another certificate

Mozilla VPN won’t connect or keeps disconnecting - How to fix

What is the Mozilla VPN kill switch?

Crash reports in Firefox for iOS

Quick fixes if your Firefox slows down

Troubleshooting speed issues on Mozilla VPN

Retrieve a Pocket crash log on Android

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

Disable Firefox Sync

Joining public WiFi while on Mozilla VPN

Compacting folders - Potential complications

How to enable Always-on VPN on Android

How do I report an issue with Firefox Relay?

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

HTTPS-First upgrades to secure connections

Server Not Found - Troubleshoot connection problems

Thunderbird makes unrequested connections

Certificate warnings in Firefox for iOS

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

Profiling Thunderbird Performance

Report Site Issues on Firefox for iOS

Connecting to unsecured networks while using Mozilla VPN

Solutions for "Can not create temp folder archive" error when installing Firefox (Windows 10)

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

How do I contact MDN Plus support?

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

How to find the Pocket app crash logs on iOS

RCS messaging and Mozilla VPN

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

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