NEW · FFmpeg.wasm · 100% Browser-Based

Free Video Merger

Concatenate multiple videos into one — no re-encode when codecs match. Drag to reorder, preview, export MP4. Browser-based, no upload.

🎬
Drop a video file
MP4 · MOV · WebM · MKV · AVI · GIF
Files stay on your device · Never uploaded

Why Do This in Your Browser?

Joining several video clips into one is conceptually the simplest video edit there is — and yet most online tools insist on re-encoding the result, which takes minutes and degrades quality slightly. FFmpeg's concat demuxer can stream-copy clips together in seconds when they share a codec and container, with zero re-encoding.

This tool does exactly that. Drop in multiple videos, drag to reorder, click Merge. When the clips share the same codec (the most common case if they all came from the same phone or camera), the merge is a stream copy — fast and bit-exact. When codecs differ, the tool transcodes the misfits to match the longest clip's codec, then concatenates.

How It Works

Stream-copy concat works by reading the bitstream of each video sequentially and writing it to a new container. No decode, no encode — every byte is preserved. The output is identical to manually splicing the source files in a hex editor (but obviously safer).

When the input clips have different codecs, resolutions, or framerates, the tool falls back to a transcode-then-concat pipeline. All clips get normalized to the dominant codec (H.264) at the dominant resolution and 30fps. This takes longer but is necessary — direct concatenation of mismatched streams produces broken playback.

Tip: Pair the Video Trimmer with the merger to build multi-cut edits — trim each segment, then merge. If your clips have mismatched codecs, run the odd ones through the Video Converter first to avoid a slow transcode-then-concat path.

Common Use Cases

Combine Phone Clips
Stitch multiple short phone recordings into one video — all share codec, so the merge is a stream copy and completes in seconds.
Highlight Reels
Trim individual highlights separately, then merge them into a single clip.
Tutorial Compilation
Combine recorded segments of a screen capture tutorial into one finished video.
Multi-Camera Rough Cut
Lay multiple camera angles end-to-end as a rough cut before fine editing in a proper NLE.
Lecture Recordings
Join multiple class sessions into a single archive video.
Loop Compilation
Stitch 10 copies of a short loop into a longer video for playback or background use.

How We Compare

Honest read on free, paid, and self-hosted options for this kind of job:

UDT Video Merger (this tool): Free, browser-based, stream-copy when codecs match. No upload, no watermark, no signup.
Clideo Merge: Free tier watermarks. $9/mo to remove. Cloud-based — every clip uploaded to their servers.
Kapwing Combine: Free 4-min cap + watermark. $16/mo. Cloud.
FreeConvert Merger: Free tier 1GB upload cap + queue waits. $9/mo. Cloud.
FFmpeg concat demuxer: Free, open-source, runs locally — fastest possible merge. Requires command line and creating a concat-list file manually. This tool wraps that exact workflow with a drag-to-reorder UI.

Frequently Asked Questions

Is the merge re-encoded?
When all input clips share codec, container, resolution, and framerate, no — it's a stream copy. When any mismatch exists, the tool transcodes the misfits to match the dominant clip, then concatenates.
How fast is the merge?
Stream-copy merges of 5–10 clips usually complete in under 10 seconds regardless of clip length. Transcode-then-concat takes proportional to total duration — roughly 30–90 seconds per 5 minutes of 1080p footage.
Are my videos uploaded anywhere?
No. The merge runs entirely in your browser via FFmpeg.wasm. The 32MB engine downloads once and caches.
How many clips can I merge?
No hard limit — but each clip stays in browser memory during the merge, so total combined size should stay under ~2GB for most laptops, ~500MB for phones.
Can I reorder clips after adding them?
Yes — drag clips up or down in the queue to set merge order. The order in the list is the order in the output.
Will there be a visible cut between clips?
Stream-copy merges have a hard cut on the exact frame where one clip ends and the next begins. For smooth transitions (crossfades, dips to black), use a proper NLE like DaVinci Resolve (free).
What if my clips have different aspect ratios?
The tool will warn you, then either letterbox or center-crop to the dominant aspect ratio. For mixed-ratio content, pre-normalize with the Video Resizer first.
Can I add audio to a silent clip during merge?
Not directly in this tool — use the Audio Extractor + a proper NLE for audio-replacement workflows. The merger only combines existing video tracks.

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