Changing folders icons in new Thunderbird

Discussion of features in Mozilla Thunderbird
Posts: 211
Joined: June 7th, 2003, 12:45 am

Post Posted February 11th, 2021, 10:49 pm

Diorser wrote:The default folder.svg icon is in omni.ja file @ chrome/classic/skin/classic/messenger/icons/folder.svg

which code is:
Code: Select all
<svg xmlns="" width="16" height="16" viewBox="0 0 16 16">
  <path fill="context-fill" d="M13 4H7.85L6.38 2.54A1.93 1.93 0 005.02 2H2a2 2 0 00-2 2v9c0 1.1.9 2 2 2h11a2 2 0 002-2V6a2 2 0 00-2-2zM5 4l1 1H2V4zm8 9H2V6h5.8v-.01c0-."/>

Many thanks so far.

I am approaching a satisfying solution.

First of all:

A SVG CAN be (somehow) cropped!
Even better: It can be cropped easily.

1. Open SVG online editor service in Firefox
Other online SVG editors are available but I did not tried them like:
2. Load (File-->Open SVG) the folder.svg file provided by Diorser
3. As you can see there is lot of space around the core folder shape:


4. Now resize folder to fit the full SVG dimensions. Play around
It looks now something like this:


5. Save the new SVG (File--->Download)
6. Rename the just saved SVG to folder.svg and copy it tot the "chrome subfolder of TB
7. Add the following instruction to userChrome.css:
Code: Select all
treechildren::-moz-tree-image(folderNameCol) {
     list-style-image: url("folder.svg") !important;
     width: 16px !important;       /* no use; can be deleted */
     height: 16px !important;      /* no use; can be deleted */

#folderTree > treechildren::-moz-tree-image {
  width: 12px !important;
  height: 11px !important;

Thats it! As you can see the folders/folder tree looks much better:


v78.7.1 A is with the resized DEFAULT folder icon
v78.7.1 B is the resized folder icon with modified folder svg.

Ok, the folders "Draft", "Inbox", "Sent", "Junk", "Trash" look like now as a normal folder.
But thats acceptable for me.

It remains one question @diorser:

How did you extract the source of folder.svg from omni.ja?

I opened omni.ja in editor and searched for the string "1H2V4zm8" but did not found it.
Is it binary encoded?


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Posts: 1009
Joined: June 22nd, 2005, 6:57 am

Post Posted February 12th, 2021, 4:33 am

thoste wrote:A SVG CAN be (somehow) cropped !

Minor remark: "somehow" as you say.
If you edit a svg file in a text editor, it's hard to interpret what cropping means. You just resize something, change data in a text file.
But agreed, a SVG graphic tool understands what you want to achieve, assuming you even don't know what a 'viewBox' svg parameter is, or the difference between a real image file (png/jpeg etc), and svg which is a text file interpreted as an image.
[SVG Tutorial](

thoste wrote:How did you extract the source of folder.svg from omni.ja ?

It depends how it has been built. In a Debian firefox build, omni.ja is just a zip file.
Mozilla built is a bit special: it's a zip file, but with some header mistakes which can be corrected like this:

Code: Select all
zip -FF omni.ja --out

To extract 'chrome/classic/skin/classic/messenger/icons/folder.svg'
Code: Select all
unzip 'chrome/classic/skin/classic/messenger/icons/folder.svg'

Posts: 149
Joined: May 30th, 2005, 7:18 am

Post Posted August 14th, 2021, 8:05 pm

morat wrote:I don't know of an addon or theme to change the folder pane styling in Thunderbird 78.

I'm using the userChrome.css file to revert the changes. If you wish to try the style, then you would need to download the following images to the chrome folder.

Thank you so much for posting this!

I noticed that TB 91 has shrunk the spacing between the icons.
Is there any way to get the spacing back to what it used to be?

Posts: 4673
Joined: February 3rd, 2009, 6:29 pm

Post Posted August 15th, 2021, 5:00 am


Try increasing the row height. I think the default row height is 1.8em in Thunderbird 78.

More info: viewtopic.php?p=14873368#p14873368

The following addon can style the folder pane in Thunderbird 91.

Phoenity Icons

Posts: 149
Joined: May 30th, 2005, 7:18 am

Post Posted August 15th, 2021, 1:38 pm

Yes, that was spot and works like a charm!

Code: Select all
#folderTree > treechildren::-moz-tree-row {
  height: 1.8em !important;

Posts: 211
Joined: June 7th, 2003, 12:45 am

Post Posted August 28th, 2021, 1:02 am

In order to replace the default TB folder icons I copied the attached file "folder.svg" to the TB subdirectory "chrome"

Then I added in userChrome.css the following statement:

treechildren::-moz-tree-image(folderNameCol) {
list-style-image: url("folder.svg") !important;

The SVG looks good. It worked in former TB installations.

After TB start, NO icons are shown any more in folder tree pane on the left.


Yes, toolkit.legacyUserProfileCustomizations.stylesheets is set to "true"

folder.svg: ... folder.svg


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Posts: 34
Joined: October 13th, 2015, 5:21 am

Post Posted August 31st, 2021, 4:24 am

If anyone is interested, I have created a project on GitLab with a userChrome.css and 3 sets of SVG folder icons that I have tested with Thunderbird 78+ (including Thunderbird Beta).

Feel free to try them and, if you have suggestions for improvement, I would appreciate constructive suggestions.

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