Upload a WebM file and convert it to MP4. When the codecs already fit the target container, the conversion is lossless and near-instant; otherwise the video is re-encoded.
Your file never leaves your device. All processing happens right in your browser, and nothing is uploaded to a server.
WebM comes out of browser screen recorders and web downloads, and promptly hits walls: iPhones, TVs, and many editors want MP4. This tool converts locally, copying streams when the MP4 container accepts them and re-encoding to H.264/AAC-compatible form when it does not.
Record in the browser, convert to MP4 here, then share, upload, or edit anywhere. Because conversion is also in-browser, the whole pipeline runs without installing software or uploading sensitive captures.