How to use it
- Drop in BMP files.
- They convert immediately, with no settings to worry about.
- Download.
The obvious upgrade for bitmaps
PNG and BMP both store images without loss, so nothing about the picture changes. The difference is that PNG compresses and BMP normally does not. For screenshots, diagrams, icons and scanned line drawings, PNG files are often a tenth of the BMP size or smaller. For photographs the saving is smaller, perhaps half, because photographic texture is hard to compress losslessly.
PNG also opens everywhere: in browsers, on phones, in every editor, in document software. BMP support outside Windows can be patchy.
Colour depth
Old software sometimes saves 8-bit BMPs with a palette of 256 colours, or even 4-bit and 1-bit files for simple graphics. These open fine and convert to standard full-colour PNGs, which can be larger than they need to be. To get back to a compact palette file, run the PNG through the PNG compressor at 256 colours; an image that only ever had 256 colours usually comes through unchanged.
Transparency
Most BMP files have no transparency. A few 32-bit BMPs carry an alpha channel, and if your browser reads it, the PNG keeps it.
BMP and PNG compared
| BMP | PNG | |
|---|---|---|
| First released | 1985 | 1996 |
| Compression | Usually none | Lossless |
| Transparency | Rarely | Yes, including soft edges |
| Animation or pages | No | Only as APNG, rarely used |
| Best for | Older Windows software and devices | Screenshots, graphics, text and transparency |
| Support | Most desktop software | Universal |
Questions people ask
Is BMP to PNG lossless?
Yes. PNG stores exactly the same pixels.
Why is a PNG of a photo still quite big?
Lossless compression cannot do much with photographic noise and texture. For photos, JPG is far smaller.
Can I convert BMP screenshots from an old program?
Yes, and PNG is the ideal format for them. Text and interface lines stay crisp.