Show HN: OnlyJPG – Client-Side PNG/HEIC/AVIF/PDF/etc to JPG

This started as a five-minute job and forty hours later...

I wanted to convert a HEIC without uploading it anywhere, so I wrestled Emscripten/WebAssembly to run Google's Jpegli inside a Web Worker. Now there's a small UI and it handles a bunch of formats.

Just about the only thing it can't decode is JXL - but there's still some JPEG XL magic in there: XYB perceptual color quantization is enabled by default via Jpegli.

The upside of all this over-engineering is privacy and compatibility: images are processed entirely on your machine and never touch a server; the output is a regular JPEG that works everywhere.

I could have used a CLI, sure — but where's the fun in that?

Would love feedback on edge cases and defaults.

Tested on Firefox, Chrome, and Safari.

Cheers!