BMP to WebP Converter

Convert BMP to WebP Online

A Windows bitmap is about the least efficient way to store a picture that is still in common use — it writes every pixel out raw. WebP is the opposite: it was built for the web, it does lossy and lossless in the same container, it carries an alpha channel, and it is now supported by every current mainstream browser. Converting a .bmp to .webp is usually the single biggest file-size win available for an image that is destined for a web page, and this converter gives you both compression modes plus the option to work back from a target file size.

How to Convert BMP to WebP

1. Upload Your BMP File: Drag your .bmp onto the page or click "+ Add Files". Queue as many bitmaps as you like and convert them in one batch.
2. Choose a Quality Preset: Quality Preset opens on "Very High (Recommended)", which is the lossy encoder at a high quality level. Drop it towards Medium or Low if you need a much smaller file and the image is photographic; raise it to Highest for the least visible loss.
3. Set Lossless and Resolution (Optional): Lossless? opens on No (Recommended) — switch it to Yes for an exact copy of the bitmap's pixels. Image resolution opens on Keep original, with a percentage, Preset Resolutions and explicit Width x Height available if you want to scale down in the same pass. You can also enter a Specific file size under Image Compression.
4. Convert and Download: Click Convert and save the .webp. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — no sign-up, no watermark, never shared or made public.

Lossy or Lossless: What We Measured

The Lossless? toggle is the fork in the road on this page. Both branches come from the same source: a 1920 x 1080 24-bit photographic bitmap measuring 6,220,854 bytes and containing 68,399 distinct colours, run through our own pipeline at the default quality level.

For reference, the same bitmap converted to a true-colour lossless PNG came out at 3,234,901 bytes, so lossless WebP was 39% smaller than lossless PNG on this image. Google's own published figure for the format is that "WebP lossless images are 26% smaller in size compared to PNGs", and that "WebP lossy images are 25-34% smaller than comparable JPEG images at equivalent SSIM quality index" — our result sits comfortably inside that story.

BMP and WebP Side by Side

Browser and Tool Support

Support is no longer a reason to avoid WebP. caniuse.com lists full support from Chrome 32, Firefox 65, Edge 18 and Safari 16, covering about 96% of tracked global traffic. The gaps are elsewhere: some desktop image editors, older document and print pipelines, and a fair number of internal enterprise tools still will not open a .webp. Treat it as a delivery format rather than a working format — keep a lossless master and export WebP for the web. If a specific tool rejects the file, BMP to PNG or BMP to JPG will get you a universally-accepted version.

Frequently Asked Questions

Is the default WebP output lossy?

Yes. Lossless? opens on No (Recommended), so the default path is the lossy encoder running at the "Very High" quality level. That is the right default for the web — in our testing it took a 6,220,854-byte bitmap down to 417,810 bytes, a 93% reduction, while keeping 50,582 of the source's 68,399 distinct colours. If you need an exact copy, switch Lossless? to Yes: the same image produced a 1,982,056-byte file that compared byte-for-byte identical to the bitmap, with zero differing pixels.

Lossless WebP or lossless PNG — which is smaller?

WebP, usually, and by a worthwhile margin. On our test image lossless WebP was 1,982,056 bytes against 3,234,901 bytes for a true-colour lossless PNG produced from the same bitmap, a 39% saving. Google publishes 26% as the typical figure across a broader corpus. PNG still wins on universality: it opens in every editor, every document tool and every browser going back decades, whereas WebP is a web-era format that some desktop software still ignores.

Does WebP keep transparency from a 32-bit bitmap?

Yes. WebP supports a full alpha channel in both its lossy and lossless modes, so alpha described by a BITMAPV4HEADER or BITMAPV5HEADER is carried through rather than being flattened onto a background. Google puts the cost of transparency in lossless mode at 22% additional bytes. Most .bmp files use the plain 40-byte BITMAPINFOHEADER and are fully opaque, in which case there is nothing to preserve and no penalty to pay.

Why is the WebP so much smaller than the bitmap?

Because BMP is barely a compressed format at all. It stores three bytes per pixel for 24-bit colour, and pads each row so its stride is a whole number of 4-byte DWORDs — which is why a 1920 x 1080 example measures exactly 6,220,854 bytes on our bench: 1,080 rows of 5,760 bytes, plus a 54-byte header. WebP applies real prediction and entropy coding on top of that, and in lossy mode also discards detail your eye is poor at noticing. Even the lossless mode, which discards nothing, cut the file by 68%.

Will a .webp open outside a web browser?

Usually, but check before you commit a workflow to it. caniuse lists full browser support from Safari 16, Chrome 32, Firefox 65 and Edge 18, so anything web-facing is safe. Desktop support is broad but not universal: current releases of the major image editors and the standard operating-system image viewers open WebP directly, while older installations may need a plugin. Print, prepress and archive pipelines are the most likely to refuse it. The safe rule is that WebP is a delivery format — if a particular application will not take it, convert a copy with BMP to PNG rather than fighting the tool.

How do I get the WebP under a specific file size?

Use Specific file size under Image Compression and enter the number you need — the encoder works back towards it and will scale the image down if quality alone cannot reach the target, telling you on the result card when it did. Doing it by hand works too: lower the Quality Preset a step at a time, and reduce the pixel dimensions under Image resolution, which is the stronger lever because pixel count falls with the square of the scale factor.

Should I convert to WebP, JPG, or PNG?

Match the destination, not the fashion. WebP for web pages and app assets — it is the smallest of the three at a given quality and handles both photographs and flat graphics well. JPG when the file has to be accepted by absolutely anything and the content is photographic. PNG when you need guaranteed lossless output, sharp text and line art, or the widest possible tool compatibility. Many teams ship WebP to browsers and keep a PNG or TIFF master on the side.

Does converting to WebP lose my image's metadata?

Assume it does. WebP can carry EXIF, XMP and ICC profile chunks, but the practical answer for this conversion is that there is very little to carry: a BMP header has essentially no metadata beyond pixel dimensions and a resolution field, with no EXIF block, no colour profile and no capture information. If your workflow depends on metadata, it needs to come from a format that actually stores it — which is one reason photographic pipelines use TIFF or JPEG rather than bitmaps.

Can I turn the WebP back into a BMP later?

Yes — WebP to BMP handles that direction. Be clear about what you get back, though: if the WebP was written in the default lossy mode, decoding it produces the compressed picture, not the original pixel values, so the round trip is not reversible. Only a file made with Lossless? set to Yes returns pixels identical to the bitmap you started with. Keep the source .bmp if the exact pixels might matter.