How the processing works
Every other online converter follows the same shape: you upload a file, a server processes it, you download the result. That design has three consequences you feel directly. You wait for the upload and the download. You accept a file size limit and a daily quota, because the operator is paying for every conversion. And your image sits on someone else’s disk for a while.
This site inverts it. The codecs — mozjpeg, libwebp, libavif, libpng, libheif — are compiled to WebAssembly and run inside a background worker in your own browser. Your file is read straight from disk into memory, converted there, and written back out as a download. There is no upload step because there is nowhere to upload to.
That is also why there are no limits. A 200 MB TIFF costs us exactly nothing, so there is no reason to cap it, no reason to meter your daily usage, and no reason to ask you to sign up. The only real constraints are your device’s memory and how fast its processor decodes pixels.
Why you can check this claim rather than trust it
“We never see your files” is easy to say and hard to verify. Here it is enforced by the browser itself: every page is served with a Content Security Policy whose connect-src 'self' directive forbids the page from opening a connection to any other host. Even if we wanted to send your image somewhere, the browser would block the request.
You can confirm it in about ten seconds. Open any converter, press F12 to open developer tools, switch to the Network tab, and convert a file. You will see the page load its code and codecs and then go completely silent while it works. Nothing carrying your image ever appears, because nothing ever leaves.
What this approach is not good at
Being honest about the trade-offs: the first conversion of a session is slower than a server-based tool, because the codec has to download before it can run. It is a few hundred kilobytes and it caches afterwards, so only the first file pays. AVIF encoding in particular takes seconds rather than milliseconds — that is the codec, not the delivery method.
A handful of formats genuinely cannot be handled in a browser today, mostly exotic camera RAW variants and PostScript-derived files. Rather than quietly routing those to a server and breaking the promise this site is built on, we simply do not offer them yet.
Pages ship wave by wave, and one goes live only when its tool actually works and its content says something specific about that conversion rather than restating a template. There are 6 format guides and 16 converters so far. The about page sets out the rest of the editorial rules — measured numbers, dated tables, and a section on every page explaining when the tool is the wrong choice.