What BMP to PNG does
BMP is the uncompressed Windows bitmap format: simple, universal on Windows, and enormous — a 1920 × 1080 screenshot is 6 MB. PNG stores exactly the same pixels with lossless compression, usually at a tenth of the size or less, and is accepted by every website, editor and messaging app. This tool converts BMP files to PNG in your browser with no change to a single pixel. Select several to receive a ZIP. Nothing is uploaded.
BMP vs PNG
| BMP | PNG | |
|---|---|---|
| Compression | None (RLE rarely used) | Lossless Deflate |
| 1920 × 1080 screenshot | ≈ 6.2 MB | ≈ 0.2–1 MB |
| Transparency | Rare (32-bit BMPs only, poorly supported) | Full alpha |
| Web support | Poor — many sites reject it | Universal |
| Origin | Windows 3.0, 1990 | 1996, designed to replace GIF |
| Where you still see it | MS Paint default, old games, embedded devices, Windows wallpaper | Everywhere |
Quality
The conversion is lossless. PNG's compression is like a ZIP for pixels — the decoded image is identical to the source. There is no quality setting because there is nothing to trade off. If you want a still smaller file for a photograph and can accept lossy compression, use BMP to JPG or the Bulk Image Converter with JPG or WebP output.
Supported BMP variants
- 24-bit and 32-bit RGB (the common cases), including 32-bit with alpha where the browser honours it.
- 8-bit, 4-bit and 1-bit palette images, expanded to full colour.
- 16-bit (565 / 555) high-colour images.
- Top-down and bottom-up row orders; RLE-compressed 4- and 8-bit BMPs in most browsers.
- OS/2 bitmap headers are generally supported; exotic bitfield layouts may fail in some browsers.
Common uses
- Uploading a Paint drawing or an old screenshot to a site that rejects BMP.
- Shrinking a folder of BMP exports from a scanner, a game or a scientific instrument before archiving.
- Attaching images to email without hitting size limits.
- Converting sprite sheets and textures from legacy software for use in modern tools.
- Sending Windows wallpapers or exports to Mac and Linux users.