BMP Format — Complete Guide & Converter

BMP (bitmap image file, also called a device-independent bitmap or DIB) is the native raster image format of Microsoft Windows. A BMP file consists of a small header describing the image's width, height, color depth and resolution, an optional color table, and then the pixel data itself, stored row by row, traditionally from the bottom of the image to the top. Most BMP files are uncompressed. That makes them extremely simple to read and write, because a program can load a BMP without any decompression library, but it also makes them very large. A 1920 × 1080 image at 24 bits per pixel takes about 6 MB regardless of what it shows. BMP supports color depths from 1-bit (black and white) through 4 and 8-bit palettes to 16, 24 and 32-bit color. An optional run-length encoding (RLE) exists for 4 and 8-bit images, and later versions of the header added alpha channels and color profiles, though many programs ignore them.

Today BMP is used mainly where simplicity matters more than size. Microcontroller and embedded display libraries (for Arduino, ESP32 and similar platforms) often load BMP images because decoding PNG or JPEG would need more memory and code. Label printers, industrial machines, medical and laboratory equipment, and legacy Windows software frequently read or write BMP. BMP is also a teaching format in programming and computer graphics courses, because its raw pixel layout makes it easy to parse and manipulate in code. Some game modding tools and older game engines still expect BMP textures and sprites. For everyday use, such as sharing, websites, email and storage, BMP is almost always converted to PNG (lossless, much smaller) or JPG (for photos).