BMP to PNG
Repack a BMP as a PNG. Same pixels, a fraction of the bytes: this is the conversion changing the size of a file without changing the picture.
Runs on your device. The file is never uploaded.
BMP to PNG repacks the same pixels, and decoding both files gives matching colours. The exception is alpha: a 32-bit BMP whose alpha bytes are all zero reads back opaque, since the format leaves that byte undefined. The bytes a BMP spends on flat colour are the bytes deflate removes, so a photograph gains far less than a screenshot does.
Questions
Does BMP to PNG upload my files?
No. BMP to PNG runs inside this browser tab, in a Web Worker on your own machine, and no part of your file is sent anywhere. There is no upload step to skip — the tool cannot reach a server even if it wanted to, and the counter on the homepage shows the number of outbound requests the page has made: zero.
How many files can I use at once?
Drop as many as you like. Each file is handled separately and comes back as its own result, so twenty files in means twenty results out.
What can I change about the result?
Nothing to configure — it does one thing, and the result is the same every time you run it on the same input.
Is BMP to PNG free, and do I need an account?
It is free and there is no account, no sign-in and no quota. Nothing is metered because nothing runs on a server — the only limit is your own device's memory, which is what decides how large a file it can handle.
Does it work offline?
Yes. The whole site is stored in your browser after the first visit, so BMP to PNG keeps working with the network off. Tools that use a machine-learning model download that model once, on first use, and run offline afterwards.
Can I use BMP to PNG outside the browser?
Yes. Every tool here is the same code on three surfaces: this page, a CLI command, and an MCP tool an AI agent can call. `bmp-to-png` is the name it goes by on all three.