How to adjust the font size of the message list and of the folder list in Thunderbird?

In Windows 10, I use Thunderbird 78.11.0 (32-Bit) as an e-mail client.

Today, suddenly the font size of the message list and of the folder list has become very small. (No changes in other applications).

How can I adjust the font size of the message list and of the folder list in Thunderbird?

4 Answers

Open the Menu and go to Preferences > General. Scroll all the way down and at the very bottom, click the Config Editor... button (accept the warning).

You're looking for layout.css.devPixelsPerPx, you can just search 'pixels' and it'll show up.

Click on layout.css.devPixelsPerPx and edit the default value of -1.0 to a scale factor you are comfortable with (example: 1.5, 2.0, 2.25, etc).

Clicking OK will allow you to immediately see your changes so you can dial it in pretty easily.

I spent a couple of hours today trying to make userChrome.css work with Thunderbird 91 on Linux Mint. No matter what I did the file was ignored. I finally found the answer: go into the config editor and search for: toolkit.legacyUserProfileCustomizations.stylesheets and set that to true. After doing that, the userChrome.css file works as expected.

layout.css.devPixelsPerPx does not scale the fonts for me and I could not get it get userChrome.css to load.

What works like a charm is to set the environment variable GDK_DPI_SCALE

E.g.

$ GDK_DPI_SCALE=2 thunderbird 

This is the actual solution to your question. This was given in the Thunderbird support forum so it's not my production.

Try this css code:

/* Threads Pane font and background*/ #threadTree > treechildren { font-size: 12pt !important; font-family: Times !important; background-color: lightgrey !important; color: navy !important; } /* Folder Pane font and background*/ #folderTree > treechildren { font-size: 12pt !important; font-family: Times !important; background-color: lightgrey !important; color: navy !important; } 

Help/Troubleshooting, Profile Folder, Open Folder, close TB, create a new folder named chrome, create a new document in chrome with a text editor, name it userChrome.css, Save as type: All files ., copy in the above code, change the numbers and colors as desired. Double-click toolkit.legacyUserProfileCustomizations.stylesheets to true in Options(Preferences)/General/Config. editor, restart TB.