Overview
BMP is the file form of the Device-Independent Bitmap (DIB) used by Windows since version 3.0 (1990). It stores pixel rows one after another, typically bottom-up, at 1 to 32 bits per pixel.
Most BMP files are uncompressed: a 12-megapixel photo takes about 36 MB. Optional RLE compression exists only for 4- and 8-bit palette images, and 32-bit alpha channels are supported inconsistently between programs.
Advantages
- +Extremely simple and fast to read and write
- +Lossless
- +Supported by Windows software and all browsers
Disadvantages
- −Very large files
- −Little metadata support
- −Transparency is not reliably supported
- −Unsuitable for the web
How BMP compression works
Usually none — pixels are stored as raw values. RLE4 and RLE8 run-length encoding is available for palette images only.
Common use cases
- Legacy Windows applications
- Embedded and industrial systems that need raw pixels
- Simple intermediate files
Browser and software support
All browsers display BMP, but it should not be used on websites because of its size.
How to convert BMP
Use the converter at the top of this page: drop your file, choose an output format and download the result. Conversions run in your browser, so nothing is uploaded.
- JPG has no transparency. Transparent areas will be filled with the background colour.
Processed locally in your browser
BMP FAQ
Why is my BMP file so large?
BMP stores every pixel without compression. Converting to PNG keeps the image lossless while typically making it several times smaller.
Does BMP support transparency?
32-bit BMPs can store alpha, but many programs ignore it. JFIF.IO writes 32-bit BMP with alpha only when the image actually has transparency.