BMP, short for bitmap, is the native image format of Microsoft Windows. It dates from the earliest versions of Windows and stores images in a simple, direct way: usually one value for every pixel, with no compression.
How BMP works
A BMP file has a small header describing the image, then the pixel data, typically 24 bits per pixel (8 each for red, green and blue), stored row by row. Variants exist with colour palettes, light run-length compression, or 32 bits per pixel including an alpha channel, but the common case is uncompressed.
What BMP is good at
- Simplicity. Very easy for software to read and write, which is why scientific instruments, industrial cameras and older programs still use it.
- No quality loss. Every pixel is stored exactly.
Where BMP falls short
- Huge files. A Full HD screenshot is about 6 MB; a 12-megapixel photo about 36 MB.
- Limited web support. Browsers can display BMP, but most websites, forms and apps won’t accept uploads.
- Weak metadata and transparency support compared with modern formats.
BMP and other formats
PNG stores the same pixels losslessly in a fraction of the space, so BMP to PNG is the natural upgrade for screenshots, diagrams and graphics. For photos, BMP to JPG makes files around 90% smaller.