I built a free AVIF to JPG converter that never uploads your files here's how it works

#webdev #javascript #tools #privacy

Most online image converters do something that bothers me — they
upload your files to their servers. Your private photos, your
design work, your documents — all going through someone else's
server just to convert a file format.

So I built one that works entirely in the browser.

How it works

The converter uses the browser's built-in Canvas API and
FileReader to handle the conversion client-side. Here's the
basic approach:

User selects AVIF file
FileReader loads it into memory locally
Canvas API decodes and re-encodes as JPG
Download link generated no server involved

Zero files leave your device. Zero uploads. Works offline after
the first page load.

Why AVIF to JPG specifically?

AVIF is a fantastic format better compression than WebP,
better quality than JPG at the same file size. But compatibility
is still catching up. Many email clients, older software, and
some social media platforms still struggle with AVIF files.

JPG meanwhile works literally everywhere. So the conversion need
is real and frequent.

What I learned building this

Browser-based file conversion is more capable than most
developers realize. The Canvas API handles surprisingly complex
image operations without any server dependency. The main
limitation is very large files browsers have memory limits
that server-side tools don't.

For most use cases though profile photos, design assets,
downloaded images browser-side conversion is faster and more
private than any server-based alternative.