Firefox can't be your default browser if another browser is set as the system default, but you can change which browser opens links and files from within Firefox itself

When you click a link in an email or document, your operating system decides which browser opens it — that's your system default. Firefox cannot override that choice. However, Firefox does let you control what happens when you click a link inside Firefox itself, and you can change your system default through your computer's settings if you want Firefox to be the one that opens links from everywhere.

The steps differ depending on whether you're on Windows, Mac, or Linux, and whether you want to change Firefox's internal behavior or your system default. This guide covers both.

Key Takeaways

  • Your system default browser (set in Windows Settings, Mac System Preferences, or Linux settings) controls which browser opens links from emails, documents, and other programs.
  • Firefox has its own internal settings for how it handles certain file types and protocols, separate from your system default.
  • On Windows 10 and later, you must change the default through Settings, not through Firefox alone.
  • On Mac, you can set Firefox as default through System Preferences, and Firefox will then open links from other applications.
  • If Firefox is already your default but links still open in another browser, check your Firefox settings for conflicting file type handlers.

Changing your system default browser on Windows

Windows 10 and later require you to change the default browser through the operating system settings, not through Firefox. Open the Windows Settings app (press the Windows key and type "Settings"), then go to Apps > Default apps. Scroll down until you see Web browser, click the current default (usually Microsoft Edge), and select Firefox from the list that appears.

Windows will then ask you to confirm. Click Switch anyway. From that point on, links clicked in Outlook, Word, emails, and other Windows programs will open in Firefox. This change takes effect immediately and does not require a restart.

If you don't see Firefox in the list, it may not be installed or Windows hasn't recognized it yet. Reinstall Firefox from mozilla.org, restart your computer, and try again.

Changing your system default browser on Mac

Open System Preferences (or System Settings on newer macOS versions), then go to General > Default web browser. A dropdown menu will appear showing all installed browsers. Select Firefox and close the window. Links from Mail, Messages, Safari, and other Mac applications will now open in Firefox.

If Firefox doesn't appear in the dropdown, make sure it's installed in your Applications folder. You can also drag Firefox from Applications into the Default web browser field if the dropdown doesn't show it.

Changing your system default browser on Linux

Linux distributions vary, but most use a settings application or a command-line tool. In GNOME (used by Ubuntu and Fedora), open Settings, go to Default Applications, and set Web to Firefox. In KDE Plasma, open System Settings, go to Startup and Shutdown > Default Applications, and select Firefox for the web browser.

If your distribution doesn't have a graphical settings panel, you can use the command line. Open a terminal and run xdg-mime default firefox.desktop x-scheme-handler/http and xdg-mime default firefox.desktop x-scheme-handler/https to set Firefox as the default for HTTP and HTTPS links.

Controlling file types and protocols within Firefox

Firefox also has internal settings for how it handles certain file types and protocols. If you want Firefox to always open PDFs, for example, rather than downloading them, you can configure that in Firefox itself. Open Firefox, go to Settings > Files & Applications, and scroll to Applications.

This list shows file types like PDF, MP3, and video formats. For each one, you can choose to open it with Firefox, save it to disk, or use a specific application. If you see a file type set to open with another program, click it and change it to Firefox or "Always ask" if you want to decide each time.

Protocols like mailto (email links) and news feeds are also listed here. If you want Firefox to handle these instead of your default email client or feed reader, you can change that too. These settings only affect what happens when you click a link inside Firefox — they don't change your system default.

Why links still open in another browser after changing the default

If you've set Firefox as your system default but links still open in another browser, check two things. First, verify the change actually took effect by going back to your system settings and confirming Firefox is listed as the default. Sometimes the change doesn't stick if another application overwrites it during installation.

Second, check Firefox's internal file type settings. Go to Settings > Files & Applications and look for any file types or protocols set to open with a different application. If you see one, click it and change it to Firefox or "Always ask". This is especially common with mailto links, which some email clients claim during installation.

If you're using a work computer or school network, your administrator may have locked the default browser setting. Contact your IT department to request a change.

Resetting Firefox to handle more file types automatically

By default, Firefox only handles a few file types automatically — mainly web pages and some media. If you want Firefox to open more types of files (like images, documents, or archives), you can configure this in the Applications settings. However, Firefox will still ask you the first time you encounter a new file type, then remember your choice.

You cannot force Firefox to handle every possible file type without being asked first. This is intentional — Firefox asks because it's safer to let you decide what to do with an unfamiliar file rather than automatically opening it with an application that might not be installed or might not handle it correctly.

Frequently Asked Questions

Can I set Firefox as default for some links but not others?

Not at the system level — your system default applies to all links from all applications. However, within Firefox, you can set different file types to open with different applications. For example, you could set PDFs to open with Adobe Reader while letting Firefox handle web pages.

Why does Edge keep becoming my default browser after Windows updates?

Windows sometimes resets the default browser during major updates. This is not a Firefox issue — it's a Windows behavior. After each major update, check your default browser setting and reset it to Firefox if needed. Some users find it helpful to disable Windows notifications about changing the default browser to avoid accidentally switching back.

What if Firefox isn't showing up as an option for default browser?

Reinstall Firefox from mozilla.org, making sure to download the correct version for your operating system (Windows, Mac, or Linux). Restart your computer after installation. If Firefox still doesn't appear, check that it's installed in the standard location — on Windows, this is usually Program Files; on Mac, Applications; on Linux, it depends on your package manager.

Does changing the default browser affect my bookmarks or passwords?

No. Changing the default browser only changes which application opens links from outside Firefox. Your bookmarks, passwords, history, and all other Firefox data remain exactly as they are.

Can I set different default browsers for different user accounts on my computer?

Yes. Each user account has its own system settings. Log in to a different account and change the default browser through that account's settings. The change applies only to that account.