How it works (and how to prove it to yourself)

SnapHEIC’s entire promise is that your photos never leave your device. This page explains the technical reality behind that claim — and shows you how to verify it independently, because you shouldn’t have to take our word for it.

The conversion runs in your browser

HEIC files are based on the HEVC codec. SnapHEIC includes a build of the libheif decoder compiled to WebAssembly — a fast, sandboxed format that runs directly in your browser. When you add a photo:

1. Your browser reads the HEIC file from disk into memory — it is never sent over the network.
2. The WebAssembly decoder turns it into raw pixels, which are drawn onto an in-memory canvas.
3. The canvas is re-encoded to your chosen format (JPG/PNG/WebP/PDF) and offered to you as a download.

On Safari, SnapHEIC uses Apple’s built-in HEIC support for an even faster result; on Chrome, Edge and Firefox it uses the bundled WebAssembly decoder. In every case the work happens locally.

Verify it yourself in 30 seconds

There are two easy ways to confirm nothing is uploaded:

• Airplane mode test: load this site, then disconnect from the internet (turn on airplane mode or pull the cable). Convert a photo — it still works, because there’s no server involved.
• DevTools Network tab: press F12, open the Network tab, then convert a photo. You’ll see no upload request carrying your image — only the static files for the page itself.

No hidden uploads, no app to install

There is no hidden upload, no tracking pixel attached to your files, and no “download our app to continue” step — SnapHEIC only ever gives you back your own converted image. You don’t have to trust that claim: the airplane-mode and Network-tab tests above let you confirm it yourself in under a minute.

Why this matters

In March 2025 the FBI warned that some “free online file converter” websites were uploading users’ files, harvesting data, and even pushing malware. SnapHEIC was built specifically to avoid that entire category of risk: nothing is uploaded, and we never ask you to install anything. Read more in is it safe to convert HEIC online?