File format guide
PNG vs ICO vs ICNS for folder icons
The artwork can look identical while the file format determines where it works. Use PNG for common macOS and Linux workflows and ICO for Windows folder properties.
Updated July 19, 2026
| Format | Best use | Transparency | FolderIcon.App |
|---|---|---|---|
| PNG | Mac Finder, Linux folders, and reusable source artwork | Yes | Export supported |
| ICO | Windows folders, shortcuts, and desktop icons | Yes | Export supported |
| ICNS | Packaged macOS application and resource icons | Yes | Not currently exported |
| SVG | Scalable source artwork and overlays | Yes | Accepted as a base or overlay |
Use PNG for a custom Mac folder
A PNG is a practical source for replacing a folder icon through Finder. Open it in Preview, copy the image content, select the small icon in the folder's Get Info window, and paste.
Use ICO for a custom Windows folder
Windows expects an icon file in the Change Icon dialog. Exporting ICO is different from simply renaming a PNG: the file has a different internal structure intended for operating-system icons.
Use PNG for a custom Linux folder
PNG is a practical exported format for Linux folder artwork. FolderIcon.App includes KDE Breeze and GNOME Adwaita bases, while the exact way you assign the image depends on the desktop environment, file manager, and icon theme you use.
When would you need ICNS?
ICNS is a macOS icon container commonly used when packaging application icons and other developer resources. You do not need it for the normal Preview-copy and Finder-paste method described in the Mac guide.
Which resolution should you choose?
128×128
Small download for compact use. Fine detail and long labels can become hard to read.
256×256
The recommended default for everyday folder icons on macOS, Windows, and Linux.
512×512
A larger master image for high-resolution displays and future reuse.
Design advice for every format
- Use a transparent background for overlay images.
- Avoid small text and intricate line work.
- Check both a large preview and a small Explorer or Finder view.
- Keep the original 512×512 artwork if you may need another export later.
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