Performance and connectivity
Deal with error messages, crashing applications, connectivity issues, and slow performance.
Captive portal detection
Description of how Firefox detects captive portal networks.
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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.
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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.
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Manage the devices linked to your Mozilla account
Find solutions to help you manage the devices and services connected to your Mozilla account.
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Connection settings in Firefox
Your organization or Internet Service Provider may offer or require you to use a proxy to connect to the Internet. Learn more.
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1 week, 6 days ago
What do the security warning codes mean?
Firefox shows you a warning page about a potential security risk when you try to connect to a secure site but your connection is not secure.
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Firefox can't load websites but other browsers can
We'll explain errors such as "Server not found" or "Unable to connect" and how to fix problems where Firefox can't access websites but other browsers can.
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Firefox blocked by macOS 15 Sequoia firewall - What you need to know
Some macOS 15 users may have Firefox blocked by the firewall. Learn about the issue and how to help Mozilla investigate.
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Resist Fingerprinting
Firefox's Advanced Preferences to resist fingerprinting can help prevent websites from uniquely identifying your device but can cause problems. Learn more.
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3 weeks, 2 days ago
Browsing history in Firefox - View the websites you have visited
Firefox keeps track of the websites you visit when you browse the Web. Learn how to view, search and sort your browsing history.
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Disable Firefox Sync
Learn how to turn off Firefox Sync if you’d like to use your Mozilla account without syncing data such as, bookmarks, history and tabs.
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How to let Firefox use the internet on your Windows computer
A "Server not found" error can be caused by Windows Firewall blocking Firefox from accessing the Internet. Learn how to configure it to allow Firefox access.
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Firefox DNS over HTTPS
DoH improves privacy by hiding domain name lookups from anyone lurking on public Wi-Fi, your ISP or others on your local network. Learn more.
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1 week, 5 days ago
DNS over HTTPS (DoH) FAQs
We have outlined a list of FAQs here that you may find helpful while getting up to speed with all that DNS over HTTPS (DoH) has to offer.
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1 week, 5 days ago
Server Not Found - Troubleshoot connection problems
If you can't connect to a website, you may see the Server Not Found error message. Learn how to troubleshoot and fix this error.
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How to resolve weak crypto error messages on Firefox
When connecting to a website that uses an invalid TLS certificate or weak encryption, Firefox will display an error page saying "Your connection is not secure".
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Address screen sharing issues with Firefox on macOS 15 Sequoia
Learn how to resolve screen sharing issues in Firefox when using macOS 15 'Sequoia' due to changes in Apple's API.
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