What is a .bmp file?
Bitmap Image File · Image · Microsoft · 1987
BMP is an old, simple Windows image format that stores pixels with little or no compression. Files are large and quality is perfect, which suits some technical uses, but for everyday sharing almost anything else is a better choice.
What is a .bmp file used for?
A BMP is close to raw pixel data plus a small header. Because it barely compresses, files are big, but there is zero quality loss and the format is dead simple for programs to read and write.
It has faded from everyday use because PNG offers the same lossless quality at a fraction of the size, with transparency to boot.
You still meet BMP in older Windows software, some scanners and simple programming exercises.
How to open a .bmp file
The .bmp format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list. For a step-by-step walkthrough, see how to open a .bmp file.
Windows
- Photos
- Paint
- any browser
macOS
- Preview
- any browser
Linux
- Image Viewer
- GIMP
Web
- Most browsers
How to convert a .bmp file
You can convert a .bmp file to PNG, JPG, WebP using a conversion tool or the export menu of an app that opens it.
Convert images free: ImageConvert
.bmp file signature (magic bytes)
Programs recognise a .bmp file by the bytes at the start of the file, not by its name. These are the signatures for BMP. For a full breakdown, see the BMP file signature page.
| Hex signature | Offset | Note |
|---|---|---|
| 42 4D | 0 | 'BM' |
See the full magic-numbers reference for every format.
Frequently asked questions
What is a .bmp file?
BMP is an old, simple Windows image format that stores pixels with little or no compression. Files are large and quality is perfect, which suits some technical uses, but for everyday sharing almost anything else is a better choice.
Why is my BMP file so big?
BMP stores pixels with little compression. Convert to PNG for the same lossless quality at a much smaller size.