Format at a glance
- Full name
- Bitmap Image File
- File extensions
- .bmp
- MIME types
- image/bmp
- Category
- Images
- Compression
- Lossless
- Transparency
- Depends on the content
- Animation
- No
- Properties
- Alpha channel
Suitable tools
What is this format?
A BMP file combines a file header, bitmap information, optional palettes and pixel rows. Rows are often padded to four-byte boundaries and may be stored bottom-up.
Different BMP variants support color depths, bit masks, alpha channels and lossless RLE compression. Applications do not implement every historic variant equally.
What is it used for?
- Windows resources and legacy software
- Uncompressed intermediate images
- Simple pixel and test data
- Legacy exchange with BMP-dependent applications
Which programs can open it?
- Windows Photos and Paint
- macOS Preview
- GIMP, Krita and Photoshop
- ImageMagick
Support across devices and browsers
Windows Photos or specialist image software opens BMP, sometimes with an extension.
Preview, Quick Look and image editors support compatible BMP files.
GIMP, Krita, ImageMagick and desktop viewers handle BMP depending on installed libraries.
Gallery and editing apps support BMP depending on the system version.
Photos, Files and image applications open supported BMP variants.
Native display and Canvas decoding depend on the browser; LocalFileLab uses local decoders when necessary.
Advantages
- Simple and documented structure
- Lossless storage of pixel values
- Broad image-software support
Disadvantages
- Usually very large files
- Inconsistent alpha and color-profile support
- Inefficient for websites and photographs
Comparison with alternatives
PNG compresses losslessly and supports transparency more consistently, replacing BMP in most workflows.
JPEG is much smaller for photographs but changes image data through lossy compression.
TIFF offers richer metadata, color spaces and compression options for professional work.
LocalFileLab support
BMP is recognized as an input. Image data is read locally through browser or WebAssembly decoders.
BMP is available as a local output; available settings depend on the format.
LocalFileLab can compress BMP locally or package it in a supported archive; already compressed content will not necessarily become smaller.
A local preview is available when the browser can display or play the content.
Complete preservation of format-specific metadata is not guaranteed.
Related formats
Frequently asked questions
Is BMP always uncompressed?
No. BMP supports RLE and other variants, although common files store pixels uncompressed or with simple masks.
Can BMP be transparent?
Some variants have an alpha channel, but interpretation is less reliable between programs than with PNG.
Why is BMP so large?
Uncompressed pixels require width times height times color depth, plus row padding and headers.