Merge Videos
- Free
- No upload
- No watermark
Quick answer
To merge videos, you join clips end to end into one continuous file. The catch is that clips only join cleanly when they share the same resolution, codec and frame rate — so this tool normalises every clip to one common format (the first clip’s frame size and frame rate, H.264 with AAC sound) as it joins them. It runs in your browser with ffmpeg.wasm and uploads nothing; a one-time ~10 MB engine loads on first use, and short clips are ideal.
Step by step
How to merge videos
- 01
Add your clips
Drop two or more videos in, then use the arrows to put them in the order you want them to play. The first use downloads and caches the ~10 MB engine.
- 02
Merge
Every clip is scaled to the first clip’s frame (with bars where the shape differs), converted to one frame rate and re-encoded, so the joins play without glitches. A clip without sound plays silent while the others keep theirs.
- 03
Download
Save the single combined MP4. Re-encoding runs on a single thread in your browser, so a longer total runtime takes a while.
In depth
Why do clips have to match to merge?
Joining video is not like joining text. Each clip is a stream of encoded frames with a specific resolution, codec, pixel format and frame rate baked in. To play as one continuous file, the joined stream has to be internally consistent — a player cannot switch from 1080p H.264 at 30 fps to 720p VP9 at 24 fps mid-file without stuttering, desyncing audio, or failing outright. That is why this tool re-encodes every clip to one common format as it joins them: slower than copying streams, but it gives a clean, seamless result even from clips that started out different.
| Property | Must match? | What the tool does |
|---|---|---|
| Resolution | Yes | Scales every clip to the first clip’s frame, adding bars where the shape differs |
| Codec | Yes | Re-encodes everything to H.264 |
| Frame rate | Yes | Converts to the first clip’s rate (at most 60 fps) |
| Pixel format | Yes | Normalised during the re-encode |
| Audio | Yes | Re-encodes to AAC stereo; a silent clip gets silence |
How do you control the order and the joins?
Clips play in the order you arrange them, top to bottom — use the arrows beside each clip to move it — so set that before exporting. The first clip also sets the frame size and frame rate of the result. A few practical tips for smooth joins:
- Trim each clip to its exact in and out points first with trim video, so the cuts land where you want.
- If a clip is the wrong shape, crop it to match the others before merging.
- Sideways clip in the batch? Rotate it upright first — a mismatched orientation will not fix itself in the join.
- Keep the clips short; total runtime is what determines how hard the encode works.
What are the browser limits?
Merging is the most demanding job in this set, because it re-encodes multiple inputs and their combined length on the single-threaded engine, all held in the tab’s memory at once. Keep the total runtime modest — a handful of short clips, not a folder of long ones — and the workbench will warn and offer cancel if the batch is too large.
Are my videos uploaded to merge them?
No. Every clip is processed in your browser through ffmpeg.wasm — read into memory, normalised, joined and handed back as a download, with nothing sent to a server. Confirm it in DevTools → Network: merging makes no upload request, and it works offline once loaded. Your footage stays on your device.
Related video and subtitle tools
Prep each clip before joining: trim, crop or rotate so they match. After merging, compress the combined file for upload, and add subtitles across the whole thing — build or convert the caption file first with the subtitle converter.
Your files never leave your device
Processed locally in your browser — nothing is uploaded. You can verify it yourself: open your browser’s developer tools, watch the Network tab, and use the tool — no upload request is ever made.
- No file is ever uploaded to a server
- Works offline after the first visit
- No account, no watermark, no limits
A little more clarity
Frequently asked questions
01How do I join two videos into one?
Add both clips, put them in order with the arrows, and merge. The tool re-encodes them to one common format — the first clip’s frame size and frame rate, H.264 with AAC sound — and joins them into a single MP4.
02Do all my clips need to be the same format?
No. MP4, MOV, WebM, MKV and AVI clips can be mixed; every clip is re-encoded to match. Clips from the same camera simply join with no visible change.
03Can I merge a portrait clip with a landscape one?
Yes. Every clip is fitted inside the first clip’s frame, so a clip of a different shape gets bars. For a full-frame result, crop the clips to the same aspect ratio before merging.
04What if one of my clips has no sound?
It plays silent in its part of the merged video, and the other clips keep their sound.
05Does the order of the clips matter?
Yes. Clips play in the order listed, top to bottom; use the arrows beside each clip to move it. Set the order before merging; rearranging afterwards means merging again.
06How many clips can I merge at once?
A handful of short clips works well. Merging re-encodes and holds the inputs in the tab’s memory, so a large batch of long clips can run the browser out of room on the single-threaded engine.
07Will merging reduce quality?
Re-encoding adds the small loss any encode does. The merge encodes at a high quality setting, so on a normal screen it is usually hard to spot. Clips larger than the first clip’s frame are scaled down to it.
08Are my videos uploaded to merge them?
No. Everything runs locally in your browser through ffmpeg.wasm. You can confirm there is no upload request in the Network tab of your developer tools.
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