BMP (Bitmap) is a raster image format native to Windows operating systems. It stores raw pixel data with no compression (or minimal RLE compression), resulting in very large files. A 1920×1080 BMP image occupies roughly 6MB, compared to about 500KB for the equivalent JPEG. BMP supports various color depths (1, 4, 8, 16, 24, and 32-bit).
BMP's main advantage is simplicity: it requires no encoding or decoding overhead, making it fast to read and write. It was the native format for Windows Paint and early Windows applications. Today, it's rarely used except in specific Windows programming contexts or when lossless uncompressed data is required for processing.
For virtually all use cases, PNG is a better alternative: lossless like BMP, but with significantly smaller file sizes due to DEFLATE compression. If you have BMP files, convert them to PNG or JPEG using FileCurve to reduce file size while maintaining quality.