On computer: Note: If you are using a screen resolution that is large eg: lots of pixels per inch/cm then everything on desktop will appear smaller.

I use 1920 x 1080 and everything looks ok.

There is a way to enlarge fonts size in Folder Pane, Message List etc You need to do the following. Make Hidden files and folder visible:

• http://kb.mozillazine.org/Show_hidden_files_and_folders

In Thunderbird:

• Help > Troubleshooting Information
• click on 'Open folder' button

a new window opens showing the contents of your Profile folder.

• Close Thunderbird now - this is important.

• Create new folder and call it chrome note the spelling - use a lower case 'c' It should be in the same place as the 'Mail' folder.

• open Notepad
• Copy everything - all the text between lines below and paste it into the Notepad document.

/*
 
* Do not remove the @namespace line -- it's required for correct functioning
 */

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); 

/*
*Make all the default font sizes eg:14 px:
*/

   * { font-size: 14px !important; } 

If this proves to be too small you can edit the 14px to say 16px etc

• Save the document as filename userChrome.css in the 'chrome' folder. Note the spelling all lower case except for the 'C'.

Start Thunderbird.

See images as guide:

Great, Toad-Hall! Thanks a lot, indeed.

I just did this and it worked, so thanks! But the arrogance of these coders, or else ignorance, boggles the imagination. "I use 1920 x 1080 and everything looks ok." Same rez here but 8pt/px text is RIDICULOUS! And to have to create and edit a CSS file while ok for me is beyond the patience. People will go back to browser email.

Hi there rootazoid,

quite strange though - but fortunately a really great turn that layout.css.devPixelsPerPx is back for me now!

Have a look here, please: http://forums.mozillazine.org/viewtopic.php?p=14777372&sid=92e66eb42c2462b2f03a6735db2e699c#p14777372

I am on a 3840x2160, setting the value to 2,4 and I am good to go.

It would seem that not all computers are the same and people do have differing requirements when it comes to eg: size of font. Are we surprised, of course not, but that's the beauty of Thunderbird, you can alter things to suit your requirements and you do not necessarilly have to use an addon.

The solutions in this question provide two methods for anyone to tailor your Thunderbird to suit your specific requirements.

re: layout.css.devPixelsPerPx Yep this is now available in Thunderbird and should help people with a quick method. Full instructions on locating where to make adjustments.

• 'Menu icon (3 lines) > Options > Options > Advanced > 'General' tab
• click on 'Config Editor' button

It may say 'here be dragons' as a type friendly warning to be careful :)

• In top search type: pixels
• Look for this line: layout.css.devPixelsPerPx

The default is -1.0

• Double click on that line to open a small window.
• clear contents and type in eg: 1.5
• click on OK

For anyone using this information. RE: the first solution: It might seem a little daunting to create a userChrome.css file, but if you can do the following then it is easy as pie and offers good control over font size. Note: there is no requirement to know code.

• Able to follow instructions
• Create a folder
• Open Notepad program
• Copy and paste provided text.
• Save a file

Chosen solution very helpful.

Changing pixels to 1.50 worked for me. Thunderbird should check the current resolution, if necessary, to make sure it displays as well as any other app. Please fix this bug.

I did the css pixel edit the UI responded nicely. But inside the emails I still get some where the text is tiny, like 7 or 8 point. Maybe there's some setting that overrides the sender's font size?

rootazoid said

Maybe there's some setting that overrides the sender's font size?

Yes, there's an option to change only the mail text size. Menu > Tools > Options > Display > Formatting > Fonts&Colors > Size . And there is also Menu > Tools > Options > Composition > General > HTML > Size.

Also, email text size can be changed by Ctrl+Mouse Wheel, if you happen to have a Mouse Wheel. There may be a keyboard equivalent for this.

All of these are independent of the Tiny Font Fix that uses the Config Editor.

Such complex design!

I've been there, done that. I have Menu > Tools > Options > Display > Formatting > Fonts&Colors > Size set to 22 for my old eyes on my 23" 1920x1080 and it fails to do anything for the offending emails.

For the fonts in messages: Options/Display/Formatting/Fonts & Colors/Advanced, set the Sizes and fonts with Fonts for: Latin and repeat with Fonts for: Other Writing Systems. Uncheck 'Allow messages to use other fonts'.

Do not change the Options/Composition settings from their defaults.

If nothing else works, including the size settings in Windows, you'll just have to reduce the resolution setting for your monitor. This will have the effect of making everything larger but displaying less (fewer pixels) on the screen. It's an unavoidable eventual tradeoff if your eyes are old, like yours and mine.

I just tried Ctrl+Mouse Wheel, didn't need to wait, worked, thanks!

David Spector said

If nothing else works, including the size settings in Windows, you'll just have to reduce the resolution setting for your monitor.

Not sure what you mean by the size settings in Windows, but of course I do know about resolution, just stubbornly refuse.

sfhowes said

Fonts for: Latin and repeat with Fonts for: Other Writing Systems. Uncheck 'Allow messages to use other fonts'.

OK I just set it up that way, at 22, for Latin and Other. Then I looked at some old emails that show in 8. They still did.

rootazoid said

I just did this and it worked, so thanks! But the arrogance of these coders, or else ignorance, boggles the imagination. "I use 1920 x 1080 and everything looks ok." Same rez here but 8pt/px text is RIDICULOUS! And to have to create and edit a CSS file while ok for me is beyond the patience. People will go back to browser email.

I agree. I'm pretty smart about stuff but I am NOT a programmer and this is ridiculous. I contribute $$ where I can instead to developers, etc. But I have no friggin' idea about how to do this and meanwhile I can't read diddly on my laptop. Please, either somebody come over to my house (in rural Oregon) or make this display option part of Thunderbird! Option B is probably easier, yes???

Ctrl+Mouse Wheel seems to be the easy way. It'd be nice if the coders would code a hook to make the Ctrl+Mouse Wheel result be the default. Eh?

KateCamp: You need to provide information on what exactly is the problem. If you need help then you must be explicit in stating where you experience the problem and the answer depends upon that information. It is also a good idea to say what OS you are using.

Font size effects various parts and some are easily set in Options > Display as mentioned by sfhowes. If the problem is a general UI including folders, message list , menus etc issue then use the instructions to access 'about: config' window via Options > Advanced to alter the pixel size. Full instructions are given in a previous comment by me and I suggest this might be a good place to start if you have a general UI issue. Some people may only want to alter eg: the Folder Pane, so would need to create a 'userChrome.css' file in which case information you can copy can be provided as a tailor made solution.

So most options for tweaking what you want are already within Thunderbird. At no point does anything require any knowledge of programming or code. But at the most it will require you to be able to follow instructions, create folders, create and save files and copy and paste provided text. There are very few people who do not have those skills.

This question has a 'Chosen Solution' and also other solutions as improvement in Options that recent versions have provided.

Fantastic, this worked perfectly. We were afraid we'd have to stop using Thunderbird because the font was so tiny. Thank you so much!

Toad-Hall: I think most of us know exactly to what I am referring in this thread. And I am perfectly capable of following directions (and don't much appreciate the tone of that remark). I've been using Thunderbird for years and every major update requires additional work to make it usable again. I tried following your directions but found them not quite adequate. And that's not the point. I join many, many other users in asking for the capabilities of the Theme Font and Size changer to be incorporated into Thunderbird to work across all platforms.