TonniTools is built to run locally in your browser. Since no data ever leaves your device, everything works, even without internet.
Trim long videos (even multi-gigabyte, 30–60 minute files) and add, replace, or remove their audio — all in your browser, with the video stream copied bit-for-bit. Nothing is ever re-encoded, so there is zero quality loss and exports are fast. Set in and out points on a timeline with keyframe-snapped trimming, a frame preview at the playhead, and a waveform of the current audio. Supports H.264, HEVC, AV1, and VP9 source video; output container follows the codec (MP4 or WebM). Audio is copied when it is already compatible, or re-encoded to AAC or Opus only when needed (where your browser supports it). Everything is streamed to disk, so memory stays low no matter how long the file is, and your video never leaves your device.