ICO is a container format for favicons and Windows icons. Current browsers open ICO, but support in programs and services is uneven.
BMP is Windows' basic bitmap that stores pixels as they are, without compression. When you convert ICO to BMP, you can open it in more places and a solid background replaces transparency. See the comparison below for what changes.
This converter reads the file itself to confirm it is ICO, then converts it to BMP right in your browser. Your image is never uploaded.
ICO vs BMP: what's the difference?
| Item | ICO | BMP |
|---|---|---|
| Compression | Lossless | None (uncompressed) |
| Transparent background | Yes | No |
| Animation | No | No |
| Introduced | 1985 | 1990 |
| Support in programs and upload forms | moderate | broad |
| Shown directly in browsers | Yes | Yes |
| Photo file size (JPG = 1) | n/a | about 12× |
What is ICO?
ICO is the format used for Windows icons and website favicons. Its distinguishing feature is that one file can hold several sizes, such as 16×16, 32×32 and 256×256.
What is BMP?
BMP is a bitmap format from Windows that mostly stores pixel values as they are, without compression. Its simple structure makes it easy for programs to read, but the files are so large that it is rarely used on the web.
What changes when you convert ICO to BMP
Transparent areas are filled with the background color you choose
BMP can't represent transparency. Transparent and semi-transparent areas are composited onto the background color in the options (white by default), so pick a matching color first if the image will be used on a dark screen.
Pixel values are preserved exactly
ICO and BMP are both lossless, so there is no change in quality. Only the file structure, compatibility and size differ.
An ICO with several sizes uses just one of them
An ICO can hold multiple sizes such as 16×16, 32×32 and 256×256. The result is one of those images. If you need a large image, use an ICO that contains the biggest size.
With no compression, the file size grows a lot
BMP stores pixels as they are. A 1920×1080 image becomes about 6MB, so unless equipment or software requires BMP, another format is recommended.
BMP has no quality setting
BMP is none (uncompressed), so the quality slider doesn't apply. Instead, when converting from ICO you can manage file size by resizing (exact width and height, or a percentage).
How the file size changes
ICO files are small icons, so the size difference after any conversion is only a few KB.
BMP opens in more places
Support for ICO in programs, document tools and upload forms is moderate, while BMP is broad. If you need to upload somewhere ICO wouldn't open, try again after converting.
When to convert
- You need to upload to a program, messenger or upload form that can't open ICO
- You need to feed legacy equipment or embedded software that only reads BMP
- You want to pull a favicon or icon file out as an ordinary image for editing or documents