Why doesn’t Thunar use your icon theme’s folder icons?

You change your icon theme and find that Thunar uses the stock Gnome icons for directories, like in this image:

Other file managers–Nautilus, Caja, PCManFM–use your theme’s folder icons, but Thunar refuses to obey. The official Xfce documentation gives you a few workarounds, but you quickly realise these are outdated and don’t have any effect.

How do you fix this?

For some reason, Thunar looks for an inode-directory icon for folder icons. Older themes often don’t have this icon, but you can easily create it as a symbolic link. Here is how you do that:

ln -s ~/.icons/my-icon-theme/scalable/places/folder.png ~/.icons/my-icon-theme/scalable/places/inode-directory.png

Adjust this command to your needs. Make sure you replace my-icon-theme with the name of your icon theme (for icon themes installed as root, look for them in /usr/share/icons/my-icon-theme). Also double check what file type your icons are. Many icon themes use .svg files (scalable vector graphics), instead of .png files (portable network graphics) as in the above example.

Once that is done, relaunch Thunar, and your directories will use the folder icons of your chosen theme.