Convert BMP to AVIF
Drop a BMP file below and get a AVIF back. The conversion happens on your own machine, so nothing is uploaded and there is no size or quantity limit beyond what your browser can hold in memory.
Drop images here
Ctrl/⌘ VPaste a screenshot or copied image
Accepts BMP
Lower means a smaller file. 75 is a good default for photos.
100% in your browser Files are never uploaded.
Why convert BMP to AVIF?
For the same picture, AVIF usually lands well under the size of the BMP original. That matters when you are trimming page weight or squeezing under an upload limit.
AVIF supports an alpha channel, so you can cut out a background after converting. The conversion itself will not invent transparency that the BMP file never had.
This is the widest gap on the site: a format from 1986 that barely compresses at all, converted to the most efficient one in mainstream use. The size difference is spectacular. Whether it is the right move depends almost entirely on what the BMP actually contains, and for a lot of BMPs the answer is no.
Before you convert
Most BMPs hold exactly the content AVIF suits least
AVIF's compression comes from AV1, designed for video — smooth gradients, photographic texture, natural detail. BMP files, by contrast, are overwhelmingly screenshots, scans, diagrams and exports from old software: flat colour and crisp text. Lossy AVIF on that material softens edges in a way that is immediately obvious on text, and the efficiency advantage narrows sharply because there is little photographic detail to be clever about. Lossless WebP or PNG will usually serve this content better.
When the BMP is a photograph, this is excellent
Scientific instruments, older cameras and some industrial equipment do write photographic data as BMP, and for that material this conversion is close to ideal — a 25 MB BMP can land under 300 KB as AVIF with no visible difference. If that describes your file, the size reduction here is the largest available anywhere on this site.
Encoding a large BMP takes real time
BMP files are big by nature and AV1 encoding is slow by nature, so this is the slowest combination available here. A large uncompressed image can take a noticeable number of seconds in the browser. That is the encoder searching for redundancy, which is where the compression comes from — it is working, not stuck.
What carries over
- Pixel dimensions
- Transparency, if the BMP had it
- Photographic content, visually intact
What does not
- Almost all of the file size
- Edge crispness on text and diagrams
- Fast encoding
BMP vs AVIF at a glance
| Property | BMP | AVIF |
|---|---|---|
| Compression | Lossless | Lossy |
| Transparency | No | Yes |
| Typical file size | 800-1200% of an equivalent JPEG | 40-55% of an equivalent JPEG |
| Compatibility | Supported by all current browsers and most apps | All current browsers; some older desktop apps lag behind |
| Usually comes from | Older Windows software and scanners | Websites optimising page weight |
Frequently asked questions
Are my BMP files uploaded anywhere?
No. The decoder and encoder are WebAssembly modules that run inside this page. The network tab may show a codec downloading the first time you use a format, but no request contains your file. On supported browsers, a codec that has already been used is cached so the same conversion can work offline.
Is there a file size or quantity limit?
There is no limit imposed by us. The practical ceiling is your device’s memory, since the image has to be held uncompressed while converting. On a typical laptop, images up to around 100 megapixels convert without trouble.
Will converting to AVIF lose quality?
AVIF is a lossy format, so some data is discarded. At the default quality setting the difference is not visible at normal viewing sizes. If you need an exact copy of the pixels, choose PNG instead.
Does it work on a phone?
Yes. The same WebAssembly modules run on mobile browsers. Conversion is slower than on a desktop because phone CPUs are weaker, and very large images are more likely to hit memory limits.
Why is my BMP file so large?
BMP stores pixels essentially uncompressed, so a single photograph can run to tens of megabytes. That alone usually makes the conversion worthwhile — expect the AVIF file to be a small fraction of the original with no visible difference.
Where does AVIF actually work?
Every major browser decodes AVIF natively, so it is safe for use on the web. Desktop applications lag further behind — plenty of image viewers and editors still cannot open it. Encoding is also noticeably slower than the other formats here, so expect a large image to take a few seconds.