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BMP: the uncompressed Windows bitmap

BMP is the Windows bitmap format. It usually stores pixels with no compression at all, so files are very large — a full-HD image is about 6 MB. It is still required by some older software and devices; for anything else, PNG stores the same pixels exactly in a fraction of the space.

BMP at a glance

File extensions
.bmp, .dib
MIME type
image/bmp
Compression
Usually none. A simple run-length option exists for palette images.
Transparency
32-bit BMPs can carry alpha, but many programs ignore it.
Animation
None.
Colour
1, 4 or 8 bits with a palette, or 16, 24 or 32 bits per pixel.
Browser support
All major browsers display BMP, but it is not used on the web.
In ImageDoctor
Opens BMP files and converts, resizes or compresses them to PNG, JPEG, WebP or AVIF. It does not save BMP.

Why BMP files are so big

A standard 24-bit BMP stores three bytes for every pixel, one each for blue, green and red, with nothing compressed. The arithmetic is simple: a 1920 × 1080 image is 2,073,600 pixels × 3 bytes ≈ 6.2 MB, whatever the picture shows. The same image as a lossless PNG is typically a fraction of that — often much less for screenshots and graphics — and as a JPEG photo, a few hundred kilobytes.

Where BMP is still used

  • Older Windows software and some industrial, medical or embedded devices that only read BMP.
  • Firmware and boot screens on some hardware, where a decoder-free format is convenient.
  • Programming exercises, because the format is simple to read and write by hand.

If a device or program asks for BMP, give it BMP. Everywhere else — email, the web, documents, storage — there is no advantage to it.

Converting BMP

BMP to PNG is lossless: every pixel is kept exactly, and the file shrinks. Choose it for screenshots, graphics and anything you may edit again. BMP to JPEG is lossy but much smaller for photographs. Both are one step in the Image Converter; add several files to convert a folder at once.

When to use BMP

  • Only when a specific program or device requires it.

When not to

  • Anything you share, upload or store. PNG keeps the same pixels in far less space.
  • Images with transparency. Alpha support in BMP is inconsistent between programs; use PNG or WebP.

Tools for BMP files

Image ConverterConvert between JPG, PNG, WebP and AVIF with control over quality, transparency and background colour.Image CompressorShrink JPG, PNG and WebP files by quality or to an exact target size, with a side-by-side quality check.Batch Image ToolsApply resize, compression, conversion and watermarks across dozens of images, then export a ZIP.

Keep reading

All image formats