How VisualRefiner converts HEIC, compresses images, and transcodes video with no server, no upload, and no account — using the Canvas API, WebCodecs, and a little WebAssembly. Most "free online converters" work like this: you pick a file, it's uploaded to a server, converted there, and sent back...
Source: [Dev.to](https://dev.to/ken_lee_fc82a8ce3a147aea6/building-image-video-conversion-that-never-leaves-the-browser-iga)