Convert between image formats without uploading

Conversion is nearly always compliance with somebody else's rule: a portal that accepts only JPEG or PNG, a design handoff that wants WebP, an old system that wants BMP. The files being reformatted to satisfy those rules are receipts, identity documents, signed pages and screenshots far more often than they are holiday photographs.

Know what each format is for before you pick. JPEG is universally accepted and is good at photographs and bad at sharp edges. PNG is lossless and correct for screenshots, diagrams and anything with text. WebP and AVIF hold detail at smaller sizes and are the sensible modern choices where the destination supports them. BMP exists for systems that demand it.

Two conversions surprise people. An animated GIF becomes a single still, its first frame, because none of the output formats carries animation. And a transparent PNG converted to JPEG loses its transparency, so a logo meant to sit on any background comes out with a solid block behind it: convert logos to WebP or AVIF, or leave them as PNG.

The check is the same and it is quick: disconnect the network, convert an image, and watch it complete and download anyway. Nothing about reading pixels and writing them out in a different container requires a server, which is why it keeps working when the network is gone.