Troubleshooting

Website will not allow Firefox to display the page if another site has embedded it

This page explains the error: "Website will not allow Firefox to display the page if another site has embedded it"

How to troubleshoot time related errors on secure websites

Learn why you might see time-related errors on HTTPS websites and how you can troubleshoot these errors by correcting your system clock.

Refresh Firefox - reset add-ons and settings

A Refresh can fix many issues by restoring Firefox to its default state while saving essential information like bookmarks and passwords.

Microsoft OAuth Authentication and Thunderbird in 2024

Changes to OAuth authentication for Microsoft 365 (formerly Office 365; often abbreviated as “o365”) business and academic hosted email accounts and services.

How to troubleshoot security error codes on secure websites

Learn about the error codes SEC_ERROR_UNKNOWN_ISSUER MOZILLA_PKIX_ERROR_MITM_DETECTED and ERROR_SELF_SIGNED_CERT on HTTPS websites and how to troubleshoot.

Profiles - Where Thunderbird stores your messages and other user data

Thunderbird saves personal information such as messages, passwords and user preferences in a set of files called a "profile".

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

Firefox has a feature that lets you see how much memory and CPU resources are being used by tabs, extensions and other processes. Learn more.

Mozilla Crash Reporter TB

The Mozilla Crash Reporter dialog box appears when Thunderbird crashes and lets you send a crash report. Learn how it works and how to access your crash reports.

Rebuilding the Global Database

Rebuilding the Global Database will initiate a re-indexing of emails and address book cards (newsgroup messages are not indexed).

I'm having problems with my Mozilla account

Get answers for common questions about your Mozilla account.

How do I report a broken site in Firefox desktop?

How to report a broken website and what information Mozilla receives when you report breakage caused by Enhanced Tracking Protection.

How to disable the Enterprise Roots preference

How to disable the Enterprise Roots preference to fix TLS connection errors caused by antivirus software, without compromising security.

Cannot send messages

If you cannot send messages with Thunderbird, this page provides a series of steps you can follow to check for common problems.

End of support for Firefox Lite

Firefox ended support for Firefox Lite.

How to reset the default user agent on Firefox

Learn how to reset your Firefox "user agent" so that websites can detect your correct browser and version and work the way they should.

Recover user data missing after Firefox update

If your bookmarks, passwords, preference settings and other data are missing, it may be available in another Firefox profile. Learn more.

Unable to use profile when you launch an older version of Thunderbird

You have launched an older version of Thunderbird

Total Cookie Protection and website breakage FAQ

Learn about Enhanced Tracking Protection and Total Cookie Protection in Firefox, and how to troubleshoot and report possible site breakage.

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

You may be selected to rate Firefox or complete a survey. You may also see a notice to update Firefox. Learn more about these messages.

How to pin and unpin Firefox from the taskbar on Windows 10 and Windows 11

Learn how to pin and unpin Firefox from the taskbar in Windows 10 and Windows 11.

FAQ Changing IMAP to POP

If your mail server supports both IMAP and POP, Thunderbird will use IMAP by default. Use these instructions to manually configure a POP account.

Troubleshoot Mode Thunderbird

How to use Thunderbird's Troubleshoot Mode to find and fix problems, especially if they are caused by add-ons.

Cannot receive messages

If you cannot receive messages, this page provides a series of steps you can use to check for common problems.

Sending and Receiving Messages on Thunderbird

How to send and receive email messages using Thunderbird.

Cannot delete messages

This article explains how to fix issues with message deletion caused by a missing or corrupted trash folder.

How to opt out of studies on Firefox for iOS

Here's how you can opt in or out of studies on Firefox iOS

X-Mouse Button Control in Firefox 110

Learn about an issue with X-Mouse Button Control in Firefox 110 for Windows.

Certificate contains the same serial number as another certificate

Why Firefox may show you a Secure Connection Failed error when you try to access the configuration page for your router and what to do.

Use the Troubleshooting Information page to help fix Firefox issues

The Troubleshooting Information page has tools and details about your Firefox installation, that can help you solve problems with Firefox.

Hyperlinks in Messages Not Working

When clicking hyperlinks in email, your default web browser should open and display their content. Learn why that may fail and why links may not be clickable.

I'm having problems confirming my Mozilla account

Here are some common solutions to help you resolve issues such as missing confirmation emails and outdated or locked Mozilla account status.

Playing 4K (Ultra-High Definition) YouTube videos in Firefox

Why the 4K option shows up for some viewers while it doesn't for others.

Firefox keeps asking me for Primary Password

How to resolve an issue where Firefox asks for a Primary (formerly "Master") Password if you have AVG or Eset Internet Security installed.

What happened to Firefox Send?

Firefox Send has been discontinued as of September 17th, 2020. Thank you for trying Firefox Send in the past.

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

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

I forgot my Password for Mozilla account and I can't sign in to MDN Plus

If you forgot your Mozilla account password, reset your password and then sign in to MDN Plus with your new password. Learn how in this article.

I can't sign in to Mozilla VPN - What should I do?

If you are having trouble signing in to Mozilla VPN, you can try any of the steps in this article to resolve most issues.

Disable Firefox Sync on a lost phone or tablet

This article describes what you should do to prevent someone from accessing your passwords on a lost device with Firefox Sync.

I've lost my Firefox Sync account information - What to do

This article explains what to do if you forget or lose your Mozilla account password and can't access your Sync account.

I can't play videos or audio on Firefox for Android 5.0 (Lollipop)

If you're using Firefox on your Nexus 9, you might have experienced a temporary issue with playing video and audio files. We'll show you how to resolve them.

Sign up for Pocket with your Mozilla account

Pocket for Firefox lets you save articles for later. All you need is a free account. Sign up or sign in with your Mozilla account.

Uninstall Firefox for iOS

If Firefox isn't for you, uninstalling it from your iOS device only takes a few seconds.

Certificate warnings in Firefox for iOS

How to bypass certificate warnings in Firefox for iOS

Some videos won't play in background

Some popular video websites have changed their settings on the server side so that videos will no longer play in the background.

Can I use my screen reader with the new Firefox?

Users on slower computers have reported problems viewing certain web pages with some screen readers in Firefox 57 and above. Learn more.

Videos don't have sound on Citrix

How to fix audio problems when you try to watch videos while using the Citrix Server on Windows.

Facebook Container isn't working

What to do if Facebook Container doesn't work.

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

How to fix Firefox drag-and-drop errors when running Windows as Administrator with UAC disabled and the Launcher Process enabled.

How to send a crash report on Firefox for Android

How to send a detailed crash report.

Compacting folders - Potential complications

Help the user understand some of the things that may go wrong when compacting.

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

Stuck with the "Can not create temp folder archive" error on 7-Zip when installing Firefox for Windows 10? This article will help you to solve the issue.

How do I uninstall Mozilla VPN?

This article describes the steps to uninstall Mozilla VPN from your device.

Difficulties opening or using a website in Firefox 100

A potential temporary solution if a web page is not opening correctly in Firefox 100.

Why do I get an error when I try to upgrade my subscription?

Users who purchased a subscription from the Apple Store or Google Play Store will receive an error message when attempting to upgrade their subscription from the website. This article explains what the error means and how to fix it.

Firefox hangs when copying with Suggested Actions enabled on Windows 11 - What to do

Firefox can freeze or stop responding when copying, with the Suggested Actions feature enabled on Windows 11. Learn how to fix the problem.

How to enable/disable the Firefox Relay icon on online fields and websites

This article will show you how to enable or disable the Relay icon on online fields and websites.

Why aren’t my add-ons working on some websites?

Learn why some Firefox extensions have been disabled on certain websites, how to manage these limits, and explore alternative solutions.

userChrome.css and .js and userContent are unsupported

userChrome.css, userChrome.js, userContent.css and userContent.js are unsupported because they can break at any time and are difficult to troubleshoot.

Inbox or Other Folder Full

Rebuilding Global Database

How can I avoid to reach the "over quota" limits of my mail server?

What do the SSLv3 error messages mean on Firefox?

When accessing a site with SSLv3, Firefox will block it and display an "Unable to connect securely" message.

Sign in to Pocket with your Mozilla account

Learn how to sign in to Pocket with your Mozilla account and resolve issues with signing in.

Accessibility not available during multi-process support

Accessibility features are not yet fully supported in multiprocess Firefox. Restart Firefox to change it back to single process mode.

Re-enable multi-process support disabled by Windows utilities

Some Windows accessibility tools might turn off Firefox's multi-process support. Here's how to re-enable it.

64-bit Firefox crashes with Citrix's XenApp VM

The API hooks from Citrix XenApp 7.13 VDA do not work with 64-bit Firefox. How to find a workaround.

I can’t play audio on a Remote Desktop Connection

How to solve a known issue with audio playback when you use Firefox on a Remote Desktop Connection.

I can't take screenshots of some websites on Firefox Lite

How to fix the screenshots problem for some sites on Firefox Lite.

File system paths on Linux are always treated as UTF-8

On Linux, the profile path is required to be valid UTF-8. Names of downloaded files are encoded in UTF-8 regardless of glibc and glib settings.

Firefox Sync takes too long to sync or send pages from my iPhone or iPad

What to do if Firefox for iOS takes a long time to sync or send URLs.

I can’t watch YouTube videos fullscreen on Firefox Lite

How to update Android WebView.

Why is each open Firefox tab showing up in the Windows volume mixer?

If each open Firefox tab shows up in your Windows volume mixer, a fix will be released in Firefox version 76. Here is a workaround in the meantime.

Unable to download files in Windows 10 when Parental Controls are on

There was a known issue in Firefox version 69 and Beta 70 that prevented you from downloading files in Windows 10 when parental controls were on.

I forgot my Mozilla account password and I can't sign in to Mozilla VPN

If you forgot the password you use to sign in to Mozilla VPN, you can reset it to a new one, then sign in to Mozilla VPN with your new password.

How to obtain the Mozilla VPN Logs

When troubleshooting issues with Mozilla VPN, our engineers can ask for logs. These don't contain any personal information, but give hints about the issue.

Workaround to make Estonian Smartcards work in Firefox 76+

Estonian Smart Cards are not working for some users in Firefox 76 and above. Here's how to make them work.

Compatibility with Exploit protection on Windows

Firefox Compatibility with Windows Exploit protection.

CCleaner is deleting Firefox extension settings in Firefox 79

Learn about workaround for a CCleaner but that's deleting saved Firefox extension settings in Firefox 79.

Profiling Thunderbird Performance

How to create a Thunderbird performance profile to find causes of high CPU load or slowness.

Report Site Issues on Firefox for iOS

Learn how to report website issues or problems in Firefox for iOS.

Firefox for iOS won't load web pages

If a website isn’t loading even after you’ve checked the Internet connection, here are a few things you can try.

How to fix an error when trying to open Telegram or Slack on Firefox

How to fix the NS_ERROR_DOM_ABORT_ERR while trying to open web.telegram.org or app.slack.com on Firefox 87 or above.

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

Fritz!box is blocked when Mozilla VPN is on.

Troubleshooting speed issues on Mozilla VPN

This article gives you a few troubleshooting tips to fix speed issues on Mozilla VPN.

How do I reset Mozilla VPN?

This article explains how to clear Mozilla VPN app data from your device.

The language of the websites I visit changes when I turn Mozilla VPN on - What to do

This article explains what to do if the language of the websites you visit changes when you use Mozilla VPN

How do I contact support for Relay Premium?

How do I contact support for Relay Premium?

I forgot my password for Mozilla account and I can't sign in to Firefox Relay

If you’ve forgotten your Mozilla account password, you can reset it to a new password, then sign in to Firefox Relay with your new password.

End of support for Firefox Lockwise

Mozilla ended support for the Firefox Lockwise app on Android and iOS, effective December 13, 2021, and integrated its functionality into Firefox mobile.

Difficulties opening or using a website in Firefox Focus for Android 100

A potential temporary solution if a web page is not opening correctly in Firefox Focus for Android 100.

How do I contact MDN Plus support if I forgot my password for Mozilla account?

Learn how to contact support if you lost access to Mozilla account and MDN Plus.

Why do I see a white screen after updating Mozilla VPN to version 2.8.3?

Some Windows users who have upgraded to Mozilla VPN version 2.8.3 are running into a white screen and are unable to access most of the features when launching the VPN. In this article, you'll find a workaround for this issue.

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

What to do if Mozilla VPN disconnects or turns off after being activated, or if websites fail to load even though Mozilla VPN is connected.

What should I do if I'm redirected to the Firefox Relay FAQ when clicking a link within an email?

After enabling the Remove email trackers Firefox Relay option, certain links in forwarded emails may redirect to our FAQ page. Learn more.

Contact support from my Mozilla VPN app

This article explains how to contact support while logged into Mozilla VPN.

How do I cancel my subscription to Firefox Relay?

At any point, you have the option to terminate your Firefox Relay subscription.

How to delete my Mozilla account via the Mozilla VPN app on Android and iOS

Learn how to delete your Mozilla account through the Mozilla VPN app. This article will walk you through the steps you need to take.

Enable or disable Local Network Access on iOS

LAN Bypass allows you to control whether or not your device can access devices on the local network while the VPN is on. Examples of these can be your network printer, your smart TV, AirDrop and CarPlay.

Troubleshoot Firefox crashes (closing or quitting unexpectedly)

Learn how to troubleshoot and fix Firefox crashes, and find out how to get more help if you're having problems solving the issue.

What to do when searches take you to the wrong search website

Firefox searches going to the wrong website can be caused by your Internet provider, an add-on, toolbar or malware. Learn how to fix this.

Firefox is stuck in Troubleshoot Mode

Learn why Firefox may start in Troubleshoot Mode (previously known as "Safe Mode") when you expect it to start normally and how to fix it.

Firefox repeatedly opens empty tabs or windows after you click on a link

Firefox may repeatedly open empty tabs or windows after you click on a link, forcing you to close Firefox. Learn how to fix this problem.

Reset your Primary Password if you've forgotten it

You can reset your Firefox primary (formerly "master") password if you forgot it. Warning: This removes all saved usernames and passwords.

Fix printing problems in Firefox

Learn how to troubleshoot and fix printing problems in Firefox.

Fix video and audio problems on Firefox for Windows N editions

If Firefox has trouble playing video or music on a Windows computer, you can install the Media Feature Pack, if it's missing. Learn more.

Problems with email and how to find help

Find out the right direction to get help using webmail in Firefox and links to support pages for popular web-based email services.

Wrong home page opens when I start Firefox - How to fix

Learn how to restore your home page if a third-party software vendor changes it so that their page always opens when you launch Firefox.

Avoid crashes - Tips and tricks

Here are some easy things you can do to avoid crashes and keep Firefox running in tip-top shape.

Latest Firefox issues

This article links to solutions for the latest Firefox issues like problems with Flash not loading or crashing.

Firefox keeps crashing at startup

If Firefox keeps crashing when you try to start it and other solutions don't work, a clean reinstall can often fix the problem.

Home page with pipe character opens extra tabs when Firefox starts

Set up Firefox to open multiple home pages replacing the pipe character (|) with %7C.

Can't add, change or save bookmarks - How to fix

This article shows you what to do if you cannot add new bookmarks or make other changes to your bookmarks.

How to run Firefox when your profile is missing or inaccessible

How to fix the error ''Your Firefox profile cannot be loaded. It may be missing or inaccessible'' so that you can start and run Firefox.