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EVERYTHING is too small in Thunderbird. How do I increase the font size of everything!

  • 25 replies
  • 76 have this problem
  • Last reply by Zenos

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It's ridiculous that Thunderbird requires an "add on" download to enable making the font size larger on EVERYTHING in the Thunderbird email program. What is Thunderbird thinking making everything so small you can barely see it?!

There has got to be a better way!!!

Please increase the size of the fonts on your program. (I know I can change the fonts and type style on outgoing emails. That's not the problem I want EVERYTHING LARGER! I want to see what I type in a message the same as my recipient will read it!

All Replies (5)

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Matt (and Zenos, and to all Whom it May Concern):

With all due respect, and in my humble opinion, I still think a slight increase in the font size of the Thunderbird interface would make the program more user-friendly. Just a slight default size increase would make a world of difference. If Mozilla wants to enable an option to increase the present Thunderbird default interface font size, they should do it in the main Thunderbird program. That's my story and I'm sticking to it. If Mozilla can make this change they will have a very nice email program.

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As explained, Thunderbird out of the box will usually work for the majority, but there are variations because of other settings on your computer which will effect what is displayed and whether this is suitable for your personal preference.

These are the Options available to you which can increase the font size of everything. It is up to you which you choose to use.

1. Increase screen resolution You have not told us what screen resolution you are using. This will effect everything you see on your desktop and all windows including Thunderbird. So if you are having an issue with the idea of using addon or creating a userChrome.css file then try this first.

Control Panel > Personalization > Display Settings A high Resolution will decrease the overall size of everything. If you are finding everything on your computer including everything in Thunderbird is too small, then lower the Resolution setting to increase the over all appearance of size. It is operated using a slide bar. then click on Apply and then OK when happy with result.

2. Use an Addon: addon will only effect Thunderbird and not other programs nor desktop.

download the addon to your computer. then install the addon following this information:

3. create css file This only effects Thunderbird.

Make Hidden files and folder visible:

In Thunderbird: Help > Troubleshooting Information click on 'show folder' button

a new window opens showing 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: usually located under All Programs > accessories > Notepad Copy all the text as specified by Zenos and paste it into the Notepad document. For ease displayed below:


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

@namespace url(""); /* set default namespace to XUL */


* Make all the default font sizes 12 px:
  • { font-size: 12px !important; }

If this proves to be too small you can edit the 12px to 14px or 16px etc

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

Restart Thunderbird.

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In case it helps anyone --

I just installed the "Theme Font & Size Changer" v33.2 plugin. I installed it into both Thunderbird and Firebox - on a Mac running Mavericks. It works GREAT !

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Matt said

They will loose me as a user if they make the interface any bitter. It is right now. As for making accessibility options a part of the program. Do you use Microsoft's sticky keys? what about mouse keys?

I don't understand "any bitter". I guess it's a typo for something. wrt UI configuration, that's not really accessibility, it's pretty basic config.

If like most people you have never heard of them, you will understand why such a feature is not in the default interface. Simply most people do not need it and there a more options than the average user can find now.

You're using "most people" a lot with no references. Neither do I understand which "them" you refer to; accessibility options? sticky keys? mouse keys?

In Microsoft's case they put in the kitchen sink and no one actually knows what is in there it is so complex. In Mozilla's case they offer the base package which is in itself complex enough and a whole raft of add-ons to customize it you your liking. In the case of the add-on in question here, it is produced by Mozilla.

I don't know what Microsoft does these days; I stopped using Windows almost 10 years ago. However, this seems to be a pretty basic config option, something that shouldn't require d/l and install of add-ons.

You apparently have a prejudice against add-ons.

I'm not sure that that's true. It seems more a case of "add-ons provide extra features and extensions, but changing the UI font, etc., shouldn't fall under that category."

That is fine, but I seriously doubt with that approach that Mozilla products are for you as add-ons are integral to their extension. Many seriously necessary features are only available though the use of add-ons.

If they are "seriously necessary features" then why aren't they part of the base product? Seems like a no-brainer, but that's my take on the subject.

Regards, David

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I use some 20 or more add-ons. Each one of them has been added because it enhances my user experience of Thunderbird.

My choices are not necessarily your choices. I wouldn't impose my preferences on you. Yet I am constantly being told that Thunderbird "should" do this or that, and I wince every time I see this, as most such suggestions or demands don't consider anyone else's use case.

If the fonts are too small, then you have a means to change things, in Thunderbird at least. No-one has yet shown me how to do the same in some Microsoft products.

Microsoft and their acolytes need to write, by and large, only for Windows. Mozilla products, OTOH, are cross-platform and necessarily are engineered in a slightly different way. One of the drawbacks is that some adjustments are not so easy. But in this case, there is a simple and reliable add-on and it works. Or you can write css for yourself. As opposed to the abominable Skype UI which is totally non-adjustable. Or Outlook with its three (count them) choices of insipid colour scheme.

If you don't like add-ons, then you have possibly missed a fundamental part of the Mozilla philosophy. Fine, use another product.

Modified by Zenos

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