Video Joiner
Merge several video clips into one continuous file, in the order you list them, with a fast or a safe merge mode.
Convert with this tool
or choose a file from your device — it is processed in this tab and never uploaded
Accepted: MP4, MOV, MKV, WebM, AVI — up to 12 clips
Files stay on your device. There is no upload, no queue and no watermark, so a conversion works even with the network switched off after the page has loaded.
Supported formats & processing
| Accepted input | MP4, MOV, MKV, WebM, AVI — up to 12 clips |
|---|---|
| Produced output | One MP4 (re-encoded) or MKV (stream copy) |
| Processing | FFmpeg.wasm (video engine, downloaded on first use) |
| Upload required | No — the file is read locally and never transmitted |
How to use this tool
- Add two or more clipsThey appear in a list in the order they will be joined.
- Reorder by removing and re-addingA removed clip is appended to the end when you add it again.
- Choose the merge methodMKV stream copy is fastest; MP4 re-encoding is safest across mixed sources.
- JoinProgress comes from the encoder as it works through the timeline.
- Preview the resultCheck the seams in the built-in player before downloading.
About this tool
Joining video is simple in principle and fiddly in practice, because clips have to agree on codec, resolution and frame rate for a clean merge. This tool offers two routes: a stream-copy concat that is instant but demands matching clips, and a re-encoding concat that normalises everything and always works.
The FFmpeg concat demuxer is used in both cases, which is the correct approach — simply appending file bytes produces a broken file with a valid first clip and garbage after it. The clip order is the order shown in the file list, and the result card reports how many clips were joined and which method was used.
Features
- Uses FFmpeg's concat demuxer, the correct joining method
- Fast stream-copy mode for clips with matching codecs
- Re-encoding mode that normalises mixed sources
- Up to 12 clips in a single job
- Clip order taken from the visible file list
- Output to MP4 or MKV
Frequently asked questions
Why did my joined file only play the first clip?
That happens when files are concatenated by appending bytes instead of using a proper concat demuxer. This tool uses the demuxer, so the result has a correct index and plays through to the end.
What happens if the clips have different resolutions?
Stream copy will fail or produce a broken file. Use the MP4 re-encoding mode, which normalises resolution, codec and frame rate as it joins.
How many clips can I join at once?
Up to 12 in a single job. For more, join in batches and then join the results.
Does joining take as long as playing all the clips?
In stream-copy mode it is nearly instant because no frames are decoded. In re-encoding mode it takes roughly the combined duration of the clips.