The icons used in the Blender user interface, as well as in add-ons, are embedded in the program libraries and are not stored separately. If you need these icons separately for something, you can get them from the Blender developers website.
Copy of Blender icons on Patreon
Previously, the Blender source code, and accordingly the icons, were hosted on the developer.blender.org domain. From Blender 3.4, all developer resources migrated to projects.blender.org.
Icons in .svg format, as before, are stored in the …/datafiles/icons_svg/ directory. However, now each icon is in a separate file.
To download icons:
- Follow the link to the official Blender development repository: https://projects.blender.org/blender/blender/src/branch/main/release/datafiles
- and open the “icons_svg” folder
You can download icons separately or together with all the source files at once.
But remember, although Blender is distributed under the GPL license, each icon has an author!