Pixsqueeze

Convert BMP to WebP

BMP files are essentially raw pixel dumps — a 4000x3000 bitmap is around 48 MB with no compression at all. Converting to WebP routinely reduces that by well over 99%, and the result works on the web, which BMP effectively does not.

Best for: Getting legacy Windows bitmaps down to a sane size and into a format browsers actually want.

What to know

  • The size reduction here is enormous simply because BMP does no compression whatsoever.
  • BMP carries no standard metadata, so there is nothing to preserve.
  • If the bitmap is a screenshot or diagram, lossless WebP will still be a fraction of the original.

About BMP

Windows' uncompressed bitmap format. Essentially a raw pixel dump with a header.

  • Usually no compression whatsoever — a 4000x3000 image is around 48 MB.
  • Poor support outside Windows.
  • No standard metadata support.
Support:
Most browsers, though it is rarely used on the web.
Transparency:
Inconsistent; usually absent.

About WebP

Google's 2010 format, now the pragmatic default for the web: meaningfully smaller than JPEG and PNG, and supported everywhere that matters.

  • Does both lossy and lossless, so it replaces JPEG and PNG with one format.
  • Transparency in lossy mode — something JPEG cannot do and PNG pays dearly for.
  • Encodes fast enough to convert hundreds of images without waiting around.
  • Universal browser support since Safari 14 in 2020.
Support:
All current browsers, including Safari 14+ and Edge. Roughly 97% of users.
Transparency:
Full alpha, in both lossy and lossless modes.

Frequently asked questions

Why are BMP files so large?
Because they are stored uncompressed. Every pixel takes three or four bytes on disk with no encoding applied, so the file size is simply width x height x bytes-per-pixel. Any modern format will be dramatically smaller.
Is converting BMP to WebP lossless?
It can be. BMP is uncompressed, so lossless WebP reproduces it exactly while still being far smaller. Lossy mode will be smaller again if the image is photographic.

Related conversions

Converting from something else? Convert any image to WebP