Online Tool Store
Video Merger
Join video clips into a single file in the order you choose, either instantly without re-encoding or re-encoded for mixed sources. Runs in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Or drag and drop video files here. Choosing again adds more clips to the end of the list.
No clips yet — they will be joined in the order you set here.
How it works
- Choose your clips, or drag and drop them onto the page. They stay on your device — nothing is uploaded at any point.
- Put them in order by dragging a clip, or with ↑ and ↓; the numbers are the play order.
- Pick fast join for clips of the same format, or compatible join for mixed sources.
- Press "Merge videos", watch the progress bar, then preview and download the result.
Why joining video is not like joining files
A video file is not a simple stream of pictures you can staple together. It is a container holding encoded streams plus an index describing where each frame lives, so the two join modes do genuinely different work:
fast join: copy compressed streams → rebuild the index
compatible join: decode every frame → normalise → re-encode → new index
Fast join never decodes a single frame, so there is no quality loss at all and the work is roughly proportional to file size — seconds, not minutes. The catch is that the streams have to be interchangeable: same codec, same resolution, same frame rate. Splice a 1080p30 clip onto a 4K60 one and the index no longer describes reality, which is why it fails rather than producing something subtly broken.
Compatible join takes the slow, safe road. Each clip is scaled to fit 1280×720 and padded rather than stretched, so a portrait phone video keeps its shape with bars either side instead of looking squashed, then everything is re-encoded at 30fps with 48kHz audio. That guarantees a single consistent stream, at the cost of one generation of quality loss and a much longer wait.
FAQ
Are my videos uploaded anywhere?
No. The joining is done by a version of FFmpeg compiled to WebAssembly that runs inside this page, so your clips are processed on your own machine. Nothing is uploaded, which is unusual for video tools and the main reason to use this one.
Which join mode should I pick?
Try fast join first — if the clips came off the same phone or camera they will share a format and it finishes in seconds without touching the video. Use compatible join when the clips come from different sources; it re-encodes everything to 720p at 30fps, which always works but takes much longer.
Why did fast join fail?
Because copying streams straight through only works when every clip has the same codec, resolution, and frame rate. A resolution mismatch — 1080p with 4K, say — is checked for and stopped before anything is written, so it fails immediately rather than handing back a file that looks fine but decodes wrong partway through. A codec or frame rate mismatch, like a phone recording with a screen capture, is caught by the join step itself instead. Either way, switch to compatible join and it will be handled.
Why does compatible join need audio on every clip?
It joins the video and audio tracks together in one pass, so a clip with no audio leaves a gap the filter cannot fill and the whole job fails. If one clip is silent, use fast join, or add a silent audio track to it first.
How big can the clips be?
Everything is held in the tab's memory at once — inputs and output together — so the practical ceiling is about 400MB in total, and you are warned above that. For a long project, merge in stages, or use a desktop editor.
Why is it slower than a desktop app?
WebAssembly runs at roughly half to a third of native speed, and it cannot use your graphics card for encoding the way a desktop app does. Fast join sidesteps this entirely by not re-encoding, which is why it is worth trying first.
How we compare
| Feature | Online Tool Store | Upload-based video sites | Desktop editors |
|---|---|---|---|
| Your footage never leaves your device | ✓ | ✗ | ✓ |
| No watermark, no sign-up, no queue | ✓ | ✗ | Free tiers often watermark |
| Lossless join when formats match | ✓ | Usually re-encodes everything | ✓ |
| Nothing to install | ✓ | ✓ | ✗ |
| Handles large or long projects | Around 400MB total | ✓ | ✓ |
| Trimming, transitions, titles | ✗ | Some offer a basic timeline | ✓ |
The case for this one is footage you would rather not upload — family video, client work, anything recorded off a screen — joined end to end with no watermark and, in fast mode, no quality loss at all. It joins; it does not edit. For trimming, transitions, or anything feature-length, a desktop editor is the right tool.