Same image, 5–10× smaller
BMP stores every pixel raw, with no compression at all — that's why a simple screenshot can weigh 4 MB. PNG stores exactly the same pixels losslessly compressed, and the same screenshot becomes a few hundred kilobytes. Nothing about the image changes: not the resolution, not a single color value.
BMP files usually come from legacy Windows software, scanners and old scientific tools — and refuse to upload to half the modern web. Converted to PNG they work everywhere. The conversion happens entirely in your browser.
Frequently asked questions
Is the conversion lossless?
Yes. PNG is a lossless format — every pixel of the BMP is preserved exactly. Only the file size changes.
Why is PNG so much smaller?
BMP is uncompressed by design. PNG applies lossless compression — like zipping the image, except image viewers can open it directly.
My BMP came from an old program — will it work?
Almost certainly. The browser's decoder handles the classic Windows BMP variants, including 8-bit palettes and 24/32-bit color.