Will the WebP file be much smaller than the source BMP?

Usually, yes. Since BMP source files are typically stored uncompressed, converting to WebP is generally a large size reduction, though it isn't a lossless conversion and a smaller result isn't guaranteed for every source image.

Does the source BMP actually carry usable alpha?

It depends on the file. Older BITMAPINFOHEADER-based BMPs have no alpha channel at all, while newer V4/V5-header BMPs can carry real per-pixel alpha — but not every BMP-writing tool sets it even when the header supports it. WebP output keeps whatever the source actually has, when the encoder supports alpha.

Are my files uploaded?

No. Conversion runs locally in your browser and does not upload your file to Looty Tools servers.

What is validated before conversion?

The file must actually be a BMP — the tool checks the "BM" header bytes, not just the filename or extension, before decoding.

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BMP to WebP Converter

Convert BMP images to WebP directly in your browser — a modern format built for efficient web delivery, encoded with adjustable quality.

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BMP to WebP processes files locally in your browser.

What BMP to WebP conversion does

Convert an old, typically uncompressed BMP image to WebP directly in your browser, with adjustable quality — a reliable way to modernize a legacy bitmap asset for the web with broader compatibility than AVIF.

How to convert BMP to WebP

Choose a BMP file.
Adjust WebP quality if needed.
Select Convert & download.
Save the .webp file from your browser downloads.

Why use this conversion

WebP gives an old BMP asset efficient, well-supported delivery for modern browsers and software, without the narrower compatibility that comes with switching to AVIF.

Transparency and output quality

This tool does not flatten onto white. Whatever alpha the browser decoded from the source BMP can remain transparent when the browser's WebP encoder supports it. Since BMP source files are typically uncompressed, converting to WebP is generally a large size reduction. The quality slider defaults to 90%; lower values shrink the file further and can introduce compression artifacts, though a smaller result is not guaranteed for every source image.

Privacy and local processing

Processing occurs locally in the browser.
Files are not uploaded to Looty Tools for conversion.
Converted files remain on your device.

Limits and known issues

Input: BMP (.bmp) only, up to 25.0 MB and 8,192 px per side.
Encoding requires canvas WebP support. Unsupported browsers show a clear error and do not increment usage.
Whether output carries real transparency depends on the source BMP's header: older BITMAPINFOHEADER files have no alpha to encode, while newer V4/V5-header files with real alpha data can be preserved by a supporting encoder.
Metadata is not preserved in the downloaded file.

Related tools

Guides

BMP to WebP FAQ

Why convert BMP to WebP?: WebP gives an old BMP asset efficient, well-supported delivery for modern browsers and software, without the narrower compatibility that comes with switching to AVIF.
Will the WebP file be much smaller than the source BMP?: Usually, yes. Since BMP source files are typically stored uncompressed, converting to WebP is generally a large size reduction, though it isn't a lossless conversion and a smaller result isn't guaranteed for every source image.
Does WebP output keep transparency?: This tool does not flatten onto white. Whatever alpha the browser decoded from the source BMP can remain transparent when the browser's WebP encoder supports it.
Does the source BMP actually carry usable alpha?: It depends on the file. Older BITMAPINFOHEADER-based BMPs have no alpha channel at all, while newer V4/V5-header BMPs can carry real per-pixel alpha — but not every BMP-writing tool sets it even when the header supports it. WebP output keeps whatever the source actually has, when the encoder supports alpha.
Are my files uploaded?: No. Conversion runs locally in your browser and does not upload your file to Looty Tools servers.
What is validated before conversion?: The file must actually be a BMP — the tool checks the "BM" header bytes, not just the filename or extension, before decoding.