Windows Bitmap, an uncompressed (or lightly compressed) raster image format.
| 0x00000000 | 424D | BM | 'BM' header |
BMP stores pixels essentially raw, which makes files large but trivial to read and write; it is still common as an intermediate format on Windows. The two-byte header 'BM' is followed by the file size and pixel-array offset.
Have a file that might be BMP? Identify it with the File Type Identifier — it reads the magic number locally, nothing is uploaded. Or browse all formats.