Yep. same add-on for both.

https://addons.mozilla.org/en-us/thunderbird/addon/theme-font-size-changer/

You can go about it differently, using a userChrome.css file to set the styling. Shout if you want to pursue that option.

Brilliant. Thank you so much. I had this in Firefox, but sadly it no longer works with Quantum, so back to miniscule menu and bookmark toolbar, but it does work on Thunderbird. Can finally read it on my high=res screen.

I have to use the userChrome.css file for both Thunderbird and Firefox on my Linux boxes, since support for this add-on in Linux was dropped some time ago.

Create a folder in your Firefox profile named chrome

In this folder, create a text file named userChrome.css

In that file place the following code:

/*
 * Do not remove the @namespace line -- it's required for correct functioning
 */
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* set default namespace to XUL */

/* 
 * Make all the default font sizes 9 pt:
 */
* { font-size: 9pt !important; }

Obviously, edit that font-size: 9pt !important; to a value that suits you. I generally use the same point size as was selected in the OS's desktop settings. You can also set the font face here, e.g.

/* 
 * Make all the default font sizes 9 pt:
 */
* { 
    font-size: 9pt !important; 
    font-family: Arial !important; 
}

A similar file named userContent.css in the same chrome folder can be used to set the size of the content of webpages (and of email if used with Thunderbird.)

Thanks for this. I'm going to have to have a little think about doing that, however, as being a 66-year-old female, I'm not your average Firefox tinkerer, and having just changed from years on a PC to a Mac, I'm struggling to find even the most basic tools for doing stuff. So chances are, any attempt to add code at this stage would result in wrecking Firefox altogether. But I'll file this away for when I figure out how to create a text file on this OS that won't damage anything.

I have the same problem, and neither the old Theme font and Size Changer, nor the new, are working. I am supposed to set preferences by picking "Theme Font and Size Changer" under tools, but it is not listed under tools.

Theme Font and Size Changer is NOT working for me, either. I deleted and reinstalled it, restarted TBird, and still no button for the add-on showing up to fix TBird's ridiculously small font problem which showed up again this morning.

Incredibly irritating that TBird developers would even think that this miniscule font size was a good idea in the first place, and that they don't give any option for increasing the font size. And that this happens again virtually every time there's a software update.

I have to use the userChrome.css file for both Thunderbird and Firefox on my Linux boxes, since support for this add-on in Linux was dropped some time ago.

Create a folder in your Thunderbird profile named chrome

In this folder, create a text file named userChrome.css

In that file place the following code:

/*
 * Do not remove the @namespace line -- it's required for correct functioning
 */
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* set default namespace to XUL */

/* 
 * Make all the default font sizes 9 pt:
 */
* { font-size: 9pt !important; }

Obviously, edit that font-size: 9pt !important; to a value that suits you. I generally use the same point size as was selected in the OS's desktop settings. You can also set the font face here, e.g.

/* 
 * Make all the default font sizes 9 pt:
 */
* { 
    font-size: 9pt !important; 
    font-family: Arial !important; 
}

A similar file named userContent.css in the same chrome folder can be used to set the size of the content of email messages.

RE: TB 52.5.2 32bit. Font size is too small ~8pt. the add-on Theme and Font Size Changer doesn't work. This occurred "overnight" with update. To have something get "hosed" (this is the nice word) with an update is unacceptable. There should be a menu font size selection, not some hack! For this functionality a hack is unacceptable.

It's just disappeared for me in Thunderbird. Had it two days, worked fine. Gone.

Hello

I posted on the same problem this week and tried a number of solutions without success but the css file solution above worked for me.

I'M VERY THANKFUL FOR ZENOS FOR THIS,

That said, I don't think most of us want an email client that works like LInux where we have we have to resort to such geeky workarounds.

I'm sick to death of my add-ons in Firefox and Thunderbird becoming redundant with every bloody update of these two softwares. You'd think font size would be a standard option in an email client.

As I said on my own thread, if we have to rely on add-ons to use the programs, the least the creators can do is NOT to screw up them up for us every 2nd week.

Thunderbird gives you a runaround about what is the path to the file. I'll not be that way. Here is the path & file name to userChrome.css:

/Users/mac/Library/Thunderbird/Profiles/ponx0hki.default/chrome/userChrome.css

where mac is your short user name. where ponx0hki is some random rubbish that's different for everyone. Just look for the .default extension.

You need to create the chrome folder if not present and the userChrome.css file if not present.

Here is the official explanation: https://developer.mozilla.org/en-US/docs/Mozilla/Thunderbird/Thunderbird_Configuration_Files Robert

Zenos and Robert: Thank you for posting this solution! But, I've tried it a few times and it isn't working for me. Tried restarting both TBIRd and my Mac entirely, and still no result from the css file. I copied and pasted verbatim, except for changing the font size; I created the file using only the coding before "Obviously,..."

Created the file in Text Editor, formatted as plain text, saved exactly per your instructions. Also tried editing a couple lines of font size in the About:config file, and...nothing.

Mac 21.5", OS High Sierra 10.13.2 TBird 52.5.2 (64-bit)

Personally, I'm finding font-family a bit more important than font-size. It's worth a try, and if your preferred font is different enough from the standard font, it is an effective test.

do you know terminal? might be the easiest to sort this out. /Applications/Utilities/Terminal short tutorial on terminal https://discussions.apple.com/docs/DOC-11071 the leading mac $ will be different for you. Don't worry.

type the command press return when done typing.

mac $ cd ~/Library/Thunderbird/Profiles
mac $ pwd
/Users/mac/Library/Thunderbird/Profiles
mac $ ls
ponx0hki.default/
mac $ # type in your directory. not mine. 
mac $ cd ponx0hki.default/
mac $ pwd
/Users/mac/Library/Thunderbird/Profiles/ponx0hki.default
mac $ cd chrome
mac $ pwd

/Users/mac/Library/Thunderbird/Profiles/ponx0hki.default/chrome

mac $ ls
userChrome.css
mac $ cat userChrome.css 

/*

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

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

/*

* Make all the default font sizes ...pt:
*/

• { font-size: 12pt !important; }

mac $ hexdump -C userChrome.css 

00000000 2f 2a 0a 20 2a 20 44 6f 20 6e 6f 74 20 72 65 6d |/*. * Do not rem| 00000010 6f 76 65 20 74 68 65 20 40 6e 61 6d 65 73 70 61 |ove the @namespa| 00000020 63 65 20 6c 69 6e 65 20 2d 2d 20 69 74 27 73 20 |ce line -- it's | 00000030 72 65 71 75 69 72 65 64 20 66 6f 72 20 63 6f 72 |required for cor| 00000040 72 65 63 74 20 66 75 6e 63 74 69 6f 6e 69 6e 67 |rect functioning| 00000050 0a 20 2a 2f 0a 40 6e 61 6d 65 73 70 61 63 65 20 |. */.@namespace | 00000060 75 72 6c 28 22 68 74 74 70 3a 2f 2f 77 77 77 2e |url("http://www.| 00000070 6d 6f 7a 69 6c 6c 61 2e 6f 72 67 2f 6b 65 79 6d |mozilla.org/keym| 00000080 61 73 74 65 72 2f 67 61 74 65 6b 65 65 70 65 72 |aster/gatekeeper| 00000090 2f 74 68 65 72 65 2e 69 73 2e 6f 6e 6c 79 2e 78 |/there.is.only.x| 000000a0 75 6c 22 29 3b 20 2f 2a 20 73 65 74 20 64 65 66 |ul"); /* set def| 000000b0 61 75 6c 74 20 6e 61 6d 65 73 70 61 63 65 20 74 |ault namespace t| 000000c0 6f 20 58 55 4c 20 2a 2f 0a 0a 2f 2a 20 0a 20 2a |o XUL */../* . *| 000000d0 20 4d 61 6b 65 20 61 6c 6c 20 74 68 65 20 64 65 | Make all the de| 000000e0 66 61 75 6c 74 20 66 6f 6e 74 20 73 69 7a 65 73 |fault font sizes| 000000f0 20 2e 2e 2e 70 74 3a 0a 20 2a 2f 0a 2a 20 7b 20 | ...pt:. */.* { | 00000100 66 6f 6e 74 2d 73 69 7a 65 3a 20 31 32 70 74 20 |font-size: 12pt | 00000110 21 69 6d 70 6f 72 74 61 6e 74 3b 20 7d 0a 0a |!important; }..| 0000011f mac $

How to get to the about:config panel Thunderbird -> preferences –> Advanced –> General and press the Config Editor...

minimum.size.th seems to be for the language th, whatever language that is. the other is for a reader, probably not the list panel.

rccharlesII said

How to get to the about:config panel Thunderbird -> preferences –> Advanced –> General and press the Config Editor... minimum.size.th seems to be for the language th, whatever language that is. the other is for a reader, probably not the list panel.

You may be on to the solution... but which suffix is for English? There is one .e! but its not in bold and the default size is 0 instead of 20 like all the others. So maybe its a different function.

I think those lines are reflecting the "minimum font size" selection found in prefs / display / formatting / advanced and English seems to be under the category "other writing systems."

maybe this? browser.display.auto_quality_min_font_size;0

skyreburn: THIS FINALLY WORKED!!

Here are the clear and simple instructions for getting and installing the modified version of Theme Font and Size Changer that worked for me: https://addons.mozilla.org/en-US/thunderbird/addon/theme-font-size-changer-for-tb/reviews/1026579/

This version apparently has the "expiration date" deleted in the code; that expiration date was the culprit behind the original TF&SC's sudden failure on Jan. 5.

Thanks for that, Mickey. That looks workable.

version 62 failed to work for me