Read every field of a BMP file - header version, bit depth, compression, palette, bitfield masks, alpha, DPI and colour space - and find out why it looks wrong or will not open. Need a smaller file? BMP to PNG is lossless.
BMP files are big because they are rarely compressed. BMP to PNG keeps every pixel and is often 90% smaller.
| Header | Size | Adds |
|---|---|---|
| BITMAPCOREHEADER | 12 bytes | OS/2 1.x - width, height, bit depth |
| BITMAPINFOHEADER | 40 bytes | Compression, DPI, palette size - the common one |
| V3 | 56 bytes | Alpha bitfield mask |
| V4 | 108 bytes | Colour space and gamma |
| V5 | 124 bytes | ICC profile and rendering intent |
Most apps read the 40-byte header. V4 and V5 files from Photoshop or GIMP can carry real transparency that older viewers ignore.
Only 32-bit BMPs can hold alpha, and many 32-bit files leave the 4th byte empty.
The analyzer samples the pixel data and tells you which one you have: real transparency, an unused 4th byte, or alpha that only some apps understand.
For transparent images on the web, convert to PNG.
Try Image Repair for damaged files.
Drop it in. The Colour line shows the bit depth and colour type, and Details explains the header fields.
Most are not. The Compression line shows None, RLE4, RLE8, bitfields, JPEG or PNG.
The analyzer samples the alpha bytes and the colour stats count see-through pixels - so you know whether the alpha is real or empty.
They usually store every pixel uncompressed: a 1920 x 1080 picture is about 6 MB. BMP to PNG keeps the exact pixels in a fraction of the size.
BMP stores pixels per metre. The analyzer converts it to DPI. Change it losslessly with the Image DPI Checker.
No. The BMP is read in your browser and never leaves your device.
