How to Change the Default Browser in Thunderbird

It's convenient having your inbox, sent box, and every other mailbox with you no matter where you go, just by logging into popular services like Gmail and Yahoo! Mail. But whether for privacy and security concerns or technical ones, there are still plenty of reasons to use a desktop-based email client, too. Among the open source choices, Mozilla Thunderbird is one of the most popular. While this software is generally user-friendly, configurable, and easy to work with, there are occasional bugs and interface decisions that make for a bumpy ride.

The Problem

Thunderbird doesn't operate alone. When you install Thunderbird on your computer, you're dropping it into a stew of other applications ... some of which may get called into action based on the contents of your emails. In the case of the uniform resource locators (URLs) you click on -- like website addresses -- Thunderbird usually passes the event off to your default web browser.

Under normal circumstances, this all goes off without a hitch. Most operating systems give you the option to choose your default web browser in some configuration screen, and most web browsers give you a way to choose them as your default option. Sometimes, however, things go wrong, and you need to know how to tell Thunderbird explicitly which web browser you want it to use.

Set the Default Browser in Thunderbird

Before you read any further, be sure that you understand this technique will not change your default web browser across all of your applications. The setting we're about to change will affect Thunderbird only.

Linux users, if you find yourself wondering whether this change will work on your particular distribution running your particular desktop environment, the answer is ... yes ... probably. If you find that you've been thinking about things like creating symbolic links to your web browser under an alias, editing /etc/alternatives/, or even diving into Thunderbird's Config Editor, STOP! The following suggestion is just as likely to work and will save you lots of time.

One last note, these instructions are for Thunderbird 11.0.1 through 17.0.8. Results in other versions may vary.

Instructions

Open Thunderbird.
Choose Preferences from the Edit menu.
The Preferences window will pop open. Select the Advanced tab.
In the bottom right of the window, press Config Editor...
Another window will open, warning you that you can potentially break Thunderbird in the Config Editor. Press I accept the risk! to move forward.
Use the search at the top of the Config Editor window to look for:
```
network.protocol-handler.warn-external.http
```

Double-click both:

network.protocol-handler.warn-external.http

and

network.protocol-handler.warn-external.https

to set their value to True.

Thunderbird config editor search results

Now, close the Config Editor.
Back on the Preferences window, select the Attachments tab.
Look for http (http) in the Content Type column. Select on the value in the Action column in the same row to see a list of choices that includes all of the web browsers currently installed on your computer. Choose the new action you'd like Thunderbird to take when it encounters a URL that starts with "http."
Now, do the exact same thing for https (https) in the Content Type column. This will cover every time Thunderbird opens a URL that begins with "https."
Press Close to exit the Preferences window.
Restart Thunderbird.

If everything worked, Thunderbird should now send clicks on URLs to whatever browser you selected in steps 5 and 6 above.

Pro Tip

You may have noticed two special things about Thunderbird's use of web browsers in this tutorial.

By following the steps above, you can set Thunderbird to use a web browser other than the default one the rest of your computer's applications use. This could be handy if you're particularly concerned about viruses coming in through emails, and you only want to view these web pages in a high-security web browser.

And, you can handle HTTP-based URLs with one browser and https-based ones with another. Again, this could be something to consider for both security and privacy issues. While you may trust your https (i.e. encrypted) requests to any of your installed web browsers, you may want your HTTP (i.e. non-encrypted) requests handled only by an entirely different browser.