BMP: the format that stores every pixel raw
BMP (Windows bitmap) is one of the oldest image formats still in circulation, and its defining trait is that it does not compress. Each pixel is written to disk as raw bytes, which made it easy for 1990s software to read and write but makes the files enormous by modern standards. The math is simple: a 1920x1080 image at 3 bytes per pixel is about 6 MB before it stores a single interesting thing. The same picture saved as JPG typically lands near 300 KB, roughly 95% smaller. That is the entire case for conversion: identical picture, one twentieth the storage, and a file that email and upload forms will actually accept. If you want lossless output instead, the PNG format is the middle ground: compressed, but exact.
Why BMP conversion is instant here
Unlike TIFF or HEIC, BMP is a format browsers still understand natively, a leftover of its Windows heritage. That means this page ships zero extra decoding code for BMP: no WebAssembly module, no JavaScript decoder, nothing to download before work starts. Your browser reads the bitmap with its built-in decoder and re-encodes it as JPG on your own device, so a batch of old Paint drawings or legacy software exports converts about as fast as you can drop it. And because no server is involved at any point, the files never leave your machine. Once converted, you can go one step smaller with JPG to WebP for images headed to the web, or compare against TIFF to JPG if your archive mixes both legacy formats.
Common questions
Why are my BMP files so large?+−
BMP is an uncompressed format: it stores every single pixel as raw bytes with no compression at all. A 1920x1080 screenshot at 24 bits per pixel is 1920 x 1080 x 3 bytes, roughly 6 MB, regardless of what the image shows. The same image as a JPG is typically around 300 KB, roughly 95% smaller, because JPG actually compresses the data.
Where do BMP files even come from these days?+−
Mostly from Windows software. MS Paint saved BMP by default for decades, older versions of Windows produced BMP screenshots, and plenty of legacy business, medical and industrial applications still export BMP because it is trivial to write. If a folder of mystery .bmp files landed on your desk, it almost certainly came from one of those.
Does converting BMP to JPG lose quality?+−
Technically yes, since JPG is lossy, but at the default 90% quality the difference is invisible for photos and screenshots in normal viewing. The BMP was never higher quality to begin with, just less efficiently stored. If the image is line art or text where you want a mathematically exact copy, convert to PNG instead, which is lossless and still far smaller than BMP.
Why is this converter so fast for BMP?+−
Because every browser can already decode BMP natively, no extra decoder needs to load, unlike formats such as HEIC or TIFF that require a bundled decoding library. Your browser reads the bitmap directly and re-encodes it as JPG using its built-in encoder. The work is a single decode and encode on your own device, so most files finish in well under a second.