Larger type in Thunderbird reading panes?

Is it possible to get the type to upsize in the folder and email list panes? I can upsize the type in the message window, but I am somewhat visually impaired and I’m having a really hard time seeing the teeny little list of emails in my inbox. I’ve looked through the list of addons but don’t see anything that meets this need. Am I missing something?


I’m not aware of an addon that will do this. There were some for earlier version of Thunderbird (I’m assuming you have 68 or higher) but they no longer work.

One relatively easy way - but not quite what you asked for - is to increase the size of the default font everywhere. This is done by changing a preference: layout.css.devPixelsPerPx
See here for more detail:

It is possible to change the font size in the folder and thread panes using a rather technical method called ‘userChrome.css’.

I’ll describe very briefly what you have to do you can decide whether it’s within your capabilities:

1 Locate your Thunderbird profile folder
2 Create a folder ‘chrome’
3 In that folder create a text file ‘userChrome.css’ (case sensitive!) containing this:

#folderTree {
    font-size: 16px !important;
    font-size: 16px !important;

Change the ‘16’ to whatever suits you.

4 If (or when) you have TB version 78 you have to enable this by setting the preference toolkit.legacyUserProfileCustomizations.stylesheets to TRUE

You’ll find more information about userChrome stylesheets, and how to locate your profile here:

userChrome.css stylesheets are a ‘legacy’ technology which has been in Firefox and Thunderbird for years. It may be removed at some stage - but my guess is it’ll be good for a few years yet!

Thank you! Yes, I’m using the latest version of TB.

I believe I can do this. I’ll try it and post my results here.

I did find this page, which offers some other tips:

I got to step 4, but cannot figure out how to toggle on the preference in the stylesheet. Can you please point me in the right direction?

In TB78:
Windows: Tools > Options (Linux: Edit > Preferances, Mac - something similar )
‘General’ - down to the bottom ‘config-editor’
Accept the warning
In search type ‘legacy’
You should see the setting toolkit.legacyUserProfileCustomizations.stylesheets and it will be ‘false’
Double-click it to toggle it to ‘true’ (goes bold to show it’s non-default)
Restart Thunderbird

Brilliant! Worked like a charm!

Thanks so much for your help!

Happy to have helped. I’ll soon need to do this on my own account!

Do remember that you have this non-standard setup. If in future you get problems with the appearance of TB, undo it before seeking help.

Will do. One last question … if I upgrade to a new version of TB, will I need to do all this again?

I don’t know - I don’t think so. If they change the appearance of the page the method might not work any more, or the css code might change. If that happens, ask on Mozillazine - if it still exists.
Maybe addons or ‘themes’ will be extended to allow this sort of useful customisation.

It would be awesome if this larger font trick could be built right into the interface as an option. It would be a huge help to many people. I’ve been very nearsighted all my life, and trust me, my vision isn’t getting better with age. I’ve used TB for years, and I like its simplicity … was hoping I wasn’t going to have to change to something else tricked out with a lot of stuff I wasn’t ever going to use.

Again, thanks so much for your help. You made my day.