App icon checklist before converting PNG to ICO

Start with a square transparent PNG

Use a square source image with transparent padding around the mark. Avoid putting the artwork right against the edge because small icon sizes need breathing room.

Check the smallest sizes

The most important test is not the largest icon. Look at 16x16, 32x32 and 48x48. If text disappears or outlines collapse, simplify the source image and export again.

Include multiple ICO sizes

Windows chooses the best bitmap inside the ICO depending on where it is shown. Keeping 16, 32, 48 and 256 pixel sizes in the same file usually gives better results across shortcuts, folders and installers.

Useful tools for this job

Use these tools when you are ready to try the workflow on your own files.