Convert BMP to AVIF — Free, Fast & Private
This is the widest efficiency gap in image formats: from a container that performs no compression whatsoever to one derived from the AV1 video codec. A 1920 × 1080 24-bit BMP occupies roughly 5.9 MB no matter what it depicts. The same picture as AVIF is often under 100 KB. A 98% reduction is unremarkable here.
Converting from raw pixels is the ideal input
Most conversions on this site are re-encodings: something already compressed, being compressed again, with the second encoder obliged to faithfully reproduce the first one’s artefacts as though they were real detail. Not this one.
A BMP is usually the original capture — raw sensor or screen data with no prior lossy pass. AVIF therefore receives clean input and can spend its entire bit budget on the actual picture instead of on preserving someone else’s compression noise. It is the single best-case scenario for any lossy encoder, and it is why the quality at a given file size here is noticeably better than converting, say, a JPEG to AVIF.
When AVIF is the right choice, and when it is not
Choose AVIF when the destination is the web and you control the markup, so you can supply a fallback. Choose it for archives of instrument or capture data where storage cost dominates and you will always open the files in a modern browser or tool.
Do not choose it when the file has to be handed to arbitrary software. BMP is understood by essentially every Windows application ever written; AVIF is not. Older desktop tools, many print workflows and a good deal of line-of-business software will simply refuse it. If the BMP came out of an instrument and has to go into an analysis package, check that package first — PNG is the safer lossless target, and still an enormous saving over BMP.
Also consider the content. AVIF is superb on photographic material. On a screenshot full of small text, a lossy codec at default settings will soften the glyph edges, and a lossless PNG is both crisper and often not much larger for that kind of image.
Encoder availability
AVIF is encoded on your own device, so the format appears in the dropdown only when your browser provides a working encoder. MiniPx probes for one first, and then checks the produced file’s magic bytes — certain browsers report AVIF support and silently return a PNG, which for a BMP-sized image would mean a multi-megabyte file wearing the wrong extension. MiniPx rejects that rather than passing it on.
Encoding AVIF is also computationally heavy. A large batch of big bitmaps will take noticeably longer than the same batch to WebP. It runs off the main thread so the page stays responsive, but do expect to wait.
If AVIF is unavailable or too slow for your batch, BMP to WebP is far quicker and still cuts around 95%. Nothing is uploaded in either case — relevant when the bitmaps are instrument or medical captures.