It may help to post screenshots of your font settings in Latin menu and in Other Writing Systems menu.

Two screenshots of the font settings in Latin and Other Writing Systems, plus one of a "Finder" window showing the strange fit of the three window-handling button-dots in the upper left, the tiny text of the message-body and Confirm window from within T'bird, and the other places (Window Menu, From) where the text is normal-sized (with Subject larger from within T'bird settings).

The tiny text in messages will zoom up just fine in T'bird, but that's a nuisance for every message (and a strangeness mystery and challenge).

This strangeness started upon migration of T'bird from my old 2013 iMac running MacOS 10.15.n to a 2019 Macbook Pro running MacOS 15.3.1, with the iMac using T'bird 123 or later and the MBP running T'bird 128 (but I am not sure because it is too small for me to read and I can't zoom it). I suspect some dissonance between T'bird and the OS, but all my poking around in MacOS System Settings and changing settings have not resolved this.

All messages, even from long before the migration, are displayed this way.

One clue might be the About Thunderbird window in "Finder," also with tiny text from T'bird in a normal-text window-frame.

I like to pretend that I know my way around Macs and apps, but this one has humbled me.

Please advise.

Thanks, Alexander

That is approx 12 point font. I suggest upping the number to 20 for latin and other writing systems and try that. Many assume the numbers are points, but they're actually pixels. Try and let us know.

I tried that; it makes no difference within message-text fields, but it does change text in the frames. Only the top SIze box will go above 16.

Also attached now is the hamburger-menu screenshot, just in case that tells us something.

And this might be another clue...

OK, I'm confused. You indicate (I think) that font size of messages is ok, and you also show that font size of non-message fields can be made quite large, so what is the exact problem??

Hello Alexander, all your screen shots are misleading since they are displayed much bigger in forums than the original. By default recent macOS versions use a 144 pixel per inch resolution in screen shots versus 72 pixel per inch in earlier versions. I have noticed that when I purchased my first iMac with a Retina 4k screen. All my screen shots were blown up when I sent them or used them in forums. Since several years I regularly edit my screens shots with Preview to resize the images to 50% of their original size. As an exemple I'll show two screen shots of the "About Thunderbird" window, one in the original size and the second resized to about 50% of its original width.

The 3rd image shows my font sizes for Latin, Other writing systems are the same. The 4th image corresponds to your screen shot of a received message displayed in a new window. Maybe you could emphasise with a new screen shot where exactly you need greater text.

To David: The "Tiny Text" screen shot of your message is typical: The text in the message-field is tiny and I don't know how to make it larger, while the framing window-texts are large (and I can make those larger and smaller). And the three window-handling button-dots in the upper left corner fit weirdly into the window-frame. the window.

Similarly, the four column-head icons on the far left of the inbox are tiny, while the text column-headers are large.

And Mapenzi, both those "About Thunderbird" images look identical on my screen. And the screen-shot of David's message shows where the anomalous tiny text is. And in the shot of the To: field pull-down, the To: field text is large while the pull-downs are tiny.

None of this was like this before the migration, which is why I intuit some OS/T'bird dissonance (but that's a guess).

In the Fonts setting, I have the top size set to 22 and the others to 16 (the highest those two go) for both Latin and Other. Still too tiny.

I am in "a little knowledge is a dangerous thing" mode, and it seems this situation is vexatious for you guys, too.

I admit, this is puzzling. Haven't seen this before. Below is a setting that applies globally, so use TINY increments in experimenting.

1. exit thunderbird
2. first make a copy of prefs.js, just in case you have problems.
3. click tools>settings>general and scroll down to config editor on right side.
4. enter layout.css.devPixelsPerPx the default is -1.0 try increasing slightly, as it can quickly get too big. try something such a 1.2 or so for starters.
5. If still too small, increase just a tiny amount, such as 1.8 or 2.0. If you increase to the point that thunderbird is impossible to read because font fills the screen. that is your clue to exit thunderbird, restore the backup of prefs.js and start over.

If you're not sure how to locate prefs.js, do this

1. - click help>moretroubleshootinginformation
2. - scroll down to 'Profile folder' and click 'open folder'
3. - exit thunderbird
4. - make copy of prefs.js
5. - restart thunderbird.