BMP is a raster image format closely associated with Microsoft Windows. The name comes from bitmap: a representation of an image as a grid of pixels. BMP files are structurally straightforward, but they are often larger and less convenient for delivery than modern compressed formats.
How BMP stores an image
A BMP begins with headers that describe details such as dimensions, color depth, and the location of pixel data. The remaining data represents rows of pixels, sometimes with a color palette and sometimes with direct color values.
Many familiar BMP files are uncompressed, which makes their storage requirements predictable but large. The specification includes compression options, yet real-world support can differ between variants and applications.
Where BMP still appears
BMP may be found in:
- legacy Windows applications;
- old software assets and installation resources;
- simple programmatic image output;
- device or industrial workflows built around established specifications; and
- archives of early desktop graphics.
Broad operating-system history does not make BMP the best general-purpose choice for a new project. It simply explains why the format is still encountered.
File size and compression
An uncompressed full-color bitmap records a large amount of data for every pixel. A high-resolution image can therefore become much larger than an equivalent PNG, JPEG, or modern web image.
Large files take longer to transfer and consume more storage. They also provide no scaling advantage: BMP remains a fixed-resolution raster image regardless of its size on disk.
Transparency and color support
BMP capabilities depend on the version and application. Some variations include alpha information, but transparency handling is not as predictable across general publishing workflows as it is with PNG. If a transparent asset needs broad support, test carefully or use a format designed for that job.
Color profiles and unusual bit depths can also be interpreted differently by older software. Preserve an original and verify converted copies when color matters.
When to convert BMP
Use PNG when you need lossless compression and broad support for a raster graphic. Use a photographic format for continuous-tone photos, and use SVG for simple artwork that needs clean scaling.
Changing BMP to PNG can reduce storage without deliberately changing the decoded pixels when the conversion is performed correctly. It does not add detail or turn the image into vector geometry.
If a BMP contains a logo, icon, or line drawing, save a lossless PNG copy at the original pixel dimensions and consider tracing it with PNG2SVG. Inspect for jagged source edges and unwanted background pixels before treating the result as finished artwork.