Image format
What is a .bmp file?
BMP is the classic Windows bitmap format. It usually stores every pixel with no compression, so it’s simple to read but very heavy.
Almost everything opens it. For nearly any modern use, PNG keeps the same pixels in a much smaller file.
fileclay opens and writes BMP
BMP vs PNG vs JPG
| BMP | PNG | JPG | |
|---|---|---|---|
| Compression | Usually none | Lossless | Lossy |
| File size | Very large | Medium | Small |
| Transparency | Limited support | Yes | No |
| Support | Almost everywhere | Everywhere | Everywhere |
| Best for | Old software | Graphics, screenshots | Photos |
When to use BMP
Good for
- Old programs that only read BMP
- Embedded systems with simple decoders
- Raw pixels for technical work
Not a good fit
- Websites: files are huge
- Email and sharing
- Storing photos: PNG or JPG take far less
How to open .bmp files
| Platform | App | Notes |
|---|---|---|
| Windows | Photos, Paint | Built in |
| macOS | Preview | Built in |
| Browsers | Chrome, Safari, Firefox, Edge | Drag the file into a tab |
| Editors | Photoshop, GIMP | Opens and saves |
Convert BMP files
How to identify a .bmp file
Every BMP starts with the two letters “BM”.
42B
4DM
It’s read here, in your browser. Only the first bytes.
Your file
What comes after
File headerType, size and where the pixels start
DIB headerWidth, height and color depth
PaletteColors, in images with few of them
PixelsThe image, usually from the bottom row up
Questions about BMP
Why are BMP files so large?
Each pixel is usually stored as it is, without compression.
Does converting BMP to PNG lose quality?
No. PNG is lossless and the file gets much smaller.
Is BMP better than PNG?
Rarely. PNG keeps the same pixels and adds real transparency support.
Does BMP support transparency?
Only in some variants, and many programs ignore it.