Performance and connectivity

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

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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

Mozilla Crash Reporter TB

What do the security warning codes mean?

Diagnose Firefox issues using Troubleshoot Mode

Troubleshoot and diagnose Firefox problems

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

Firefox can't load websites but other browsers can

Resist Fingerprinting

Rebuilding the Global Database

DNS over HTTPS (DoH) FAQs

Troubleshoot Mode Thunderbird

How do I report a broken site in Firefox desktop?

How to let Firefox use the internet on your Windows computer

Firefox DNS over HTTPS

Use the Troubleshooting Information page to help fix Firefox issues

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

Firefox hangs or is not responding - How to fix

How to reset the default user agent on Firefox

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

How can I tell if Mozilla VPN is connected?

Certificate contains the same serial number as another certificate

Where to go for developer support

Disable Firefox Sync

Websites look wrong or appear differently than they should

Server Not Found - Troubleshoot connection problems

Quick fixes if your Firefox slows down

Unload inactive tabs to save system memory in Firefox

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

How to enable Always-on VPN on Android

Connecting to unsecured networks while using Mozilla VPN

Compacting folders - Potential complications

HTTPS-First upgrades to secure connections

Rate your Firefox experience, surveys and out of date messages (Heartbeat)

Certificate warnings in Firefox for iOS

Joining public WiFi while on Mozilla VPN

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

Firefox takes a long time to start up

Firefox does not work - Common fixes to get you back up and running

Some videos won't play in background

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

What is the Mozilla VPN kill switch?

Report Site Issues on Firefox for iOS

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

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 Focus for Android 100

Search your browsing history in Firefox for iOS

How do I report an issue with Firefox Relay?

X-Mouse Button Control in Firefox 110

Retrieve a Pocket crash log on Android

Firefox uses too many CPU resources - How to fix

Memory constraints, Firefox performance and Firewalls

Thunderbird makes unrequested connections

Rebuilding Global Database

How to resolve weak crypto error messages on Firefox

64-bit Firefox crashes with Citrix's XenApp VM

How to obtain the Mozilla VPN Logs

How to send a crash report on 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

Fritz!box isn't working when Mozilla VPN is on

Troubleshooting speed issues on Mozilla VPN

Difficulties opening or using a website in Firefox 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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