ICO (Windows Icon)
ICO is the Windows icon container, and the traditional format for a website’s favicon.
- File extension
- .ico
- MIME type
- image/x-icon
- Compression
- Lossless
- Transparency
- Yes, full alpha channel
- Animation
- No
- Type
- Raster (pixels)
Where ICO files come from
Website favicons and Windows application icons.
Universal for its one job: favicons and Windows icons.
What ICO is good at
- Holds several sizes in one file so each context picks the sharpest
- The one favicon format every browser understands, including very old ones
- Supports transparency
Where ICO falls short
- Only useful for icons — sizes are capped at 256x256
- Not a general-purpose image format
- Awkward to create in most image editors
Should you use ICO?
Use it when the image must survive editing and re-saving without degrading, or when transparency matters. Avoid it for large photographs that only need to be viewed, where a lossy format will be a fraction of the size with no visible difference.
Convert from ICO
Convert to ICO
Frequently asked questions
What is ICO (Windows Icon)?
ICO is the Windows icon container, and the traditional format for a website’s favicon. Universal for its one job: favicons and Windows icons.
How do I open ICO files?
Any tool that lists ICO support will open one. If yours will not, the quickest fix is to convert it to a format your software already understands — the converters linked on this page do that in your browser without uploading the file.
Is ICO lossy or lossless?
ICO is lossless — every pixel is stored exactly, and re-saving it repeatedly costs you nothing in quality. The trade-off is a larger file.
Does ICO support transparency?
Yes, ICO carries a full alpha channel, so soft edges and drop shadows survive intact. Converting to a format without alpha — JPG most commonly — flattens those areas onto a solid colour.