BMP Header and DIB Info Viewer
Drop in a Windows bitmap (.bmp) to read its BITMAPFILEHEADER and DIB info header: exact pixel dimensions, bits per pixel, compression method, print resolution in DPI, palette size, and where the pixel data starts. The file is parsed entirely in your browser and never uploaded.
How to view a BMP header
- Drag a .bmp file onto the box, or click browse to pick one.
- Read the dimensions, bit depth, compression, and DPI that appear instantly.
- Check the data offset and palette size to understand the file layout.
Examples
A 24-bit photo bitmap
screenshot.bmp (an uncompressed 24-bit BMP)
1920 x 1080, 24 bpp, BI_RGB (none), 96 DPI, no palette
Frequently asked questions
Is my BMP uploaded anywhere?
No. The file is read and parsed entirely in your browser using JavaScript. Nothing is sent to a server, so even private images stay on your device.
How does it read the header?
BMP stores its fields little-endian. The tool reads the 14-byte BITMAPFILEHEADER (the BM signature, file size, and pixel data offset) and the DIB info header that follows it (width, height, bit depth, compression, resolution, and palette count).
Why is the height shown as positive when the file says negative?
A negative biHeight means the rows are stored top-down instead of the usual bottom-up order. The viewer reports the absolute height and flags it as a top-down bitmap separately.
What does the compression field mean?
Most BMP files use BI_RGB, which is uncompressed. Other values indicate run-length encoding (BI_RLE8 or BI_RLE4) or bit-field masks (BI_BITFIELDS) used by 16 and 32-bit images.
How is DPI calculated?
BMP records resolution in pixels per meter. The tool divides by 39.3701 (the number of inches in a meter is 1 / 0.0254) and rounds to give dots per inch. A value of 0 means the resolution was not set.
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