How to use
- Add one or more videos; the container and codecs of each are detected.
- Choose the output format, and optionally a video codec or a maximum resolution. The page lists which encoders your browser has.
- Convert, check whether each stream was copied or re-encoded, and download.
Worked example
A .mov with H.264 video and AAC audio converts to .mp4 by copying both streams (no re-encoding, so quality is unchanged and it takes seconds). A WebM with VP9/Opus becomes H.264/AAC in MP4.
Supported formats and limits
| Input | MP4, MOV, WebM, MKV, MPEG-TS |
|---|---|
| Output | MP4, WebM, MOV, MKV, M4A, MP3, WAV, Ogg Opus |
| Limits | Input files up to 4 GB are read in pieces; the converted file is built in memory, so outputs above about 2 GB may fail. Needs a browser with WebCodecs (current Chrome, Edge, Safari 17+ or Firefox 130+). Other browsers are told so before any work starts. |
| Engine | Mediabunny (WebCodecs): streams are copied when compatible, otherwise re-encoded; MP3 via a WebAssembly encoder |
Limitations
- Which codecs can be encoded depends on the browser and device (for example, H.265 encoding is often unavailable); the tool checks before converting.
- HEVC (H.265) decoding depends on your device and browser.
- AVI, WMV and FLV files cannot be read by browsers' media engines and are not supported.
- Only the main video and audio track are kept; subtitle and extra audio tracks are left out.
Questions
Does converting reduce quality?
Not when the streams can be copied. With Automatic, H.264 video and AAC audio from a MOV go into MP4 unchanged, which takes seconds. When the target format needs another codec, or you choose a smaller resolution, the video is re-encoded.
Is extracted audio copied as is?
No. The audio track is re-encoded into the format you pick, even AAC to M4A at the same bitrate.
Which tracks are kept?
The main video track and the main audio track. Subtitle tracks and extra audio tracks are left out.
Privacy
Runs on your device. Files and text are processed in this browser tab and are not uploaded.
See the privacy policy for how toolsdocks handles data.