A short history
BMP (Bitmap) is a Microsoft/IBM format dating to the earliest days of Windows and OS/2. It was designed for simplicity and device-independence rather than efficiency, at a time when storing an image as raw pixels was perfectly acceptable and compression was a luxury.
How it works
A BMP is about as simple as an image gets: a small header followed by the raw pixel values, almost always uncompressed. That makes it trivial for any program to read or write, but the files are enormous — a photo can be tens of megabytes where a JPEG would be a few hundred kilobytes. Standard BMP has no meaningful transparency.
When & how to use it
There’s rarely a reason to choose BMP today. It shows up in legacy Windows tooling, in raw intermediate steps of an image pipeline, or when a specific program simply demands it. For storage or sharing, convert to PNG (lossless, far smaller) or JPEG (for photos).
- A Microsoft/IBM format from the early Windows/OS-2 era.
- Stores raw, uncompressed pixels — simple to read, very large.
- No practical transparency support in the standard form.
- Almost always better replaced by PNG or JPEG today.