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BMP to PNG Converter

Turn an uncompressed Windows bitmap into a much smaller PNG without touching a single pixel value.

BMP file

Drop a file here, paste from the clipboard, or choose one

BMP, processed in this tab

PNG result

The result appears here

Result
Runs locally in your browser

About the BMP to PNG Converter

A BMP stores every pixel as raw bytes, which is why a plain 1920 by 1080 screenshot saved from Paint weighs about six megabytes. PNG keeps exactly the same pixel values but runs them through DEFLATE with a per-row filter, so the identical picture usually lands between a fifth and a twentieth of that size. This converter decodes the bitmap you choose, redraws it on a canvas, and asks the browser for a PNG, so the result is byte-for-byte the same image at a fraction of the weight.

Bitmaps with 1, 4, 8, 16, 24 and 32 bits per pixel are all handled, because the decoding is done by the browser image pipeline rather than by hand-written parsing. Top-down bitmaps, which some capture utilities write with a negative height field, load correctly too. If a 32-bit BMP carries an alpha channel, the transparency survives the trip into PNG.

One thing to watch: RLE-compressed 8-bit bitmaps are rare and some browsers refuse them, in which case you will see a decoding message instead of a result. Pick a smaller maximum width first if the bitmap is a scan and you only need a web copy. When you want the opposite direction, PNG to BMP writes a 24-bit bitmap back out.

How to use

  1. Drop the .bmp file on the left pane, or click it to browse.
  2. Leave Max width on Original to keep full resolution, or pick a smaller width for the web.
  3. Click Download to save the PNG next to your bitmap.

Common questions

Does converting BMP to PNG lose any quality?
No. PNG is a lossless format, so the saved file decodes back to exactly the same pixels the bitmap held.
Why is my PNG so much smaller than the BMP?
BMP stores raw pixel bytes with no compression at all, while PNG compresses runs of similar pixels. Flat graphics and screenshots shrink the most.
Can it read a 32-bit BMP with transparency?
Yes, and the alpha channel is carried into the PNG, so semi transparent corners stay transparent.
Is there a file size limit?
The limit is your device memory. Bitmaps of 50 megabytes or so convert without trouble on a normal laptop.