Merge videos

Merge Videos Online — Combine Clips Into One File

Drop in two or more clips, reorder, hit merge. The output is one file you can play, share, or hand to an editor. Runs entirely in your browser via FFmpeg compiled to WebAssembly — your videos never get uploaded.

  • No upload
  • No signup
  • Playable MP4 output
  • Up to 800 MB total
  • Audio preserved
Clips are normalized before merging so the final download plays past the first segment and keeps audio in later clips. Very large merges are still better handled with a native desktop editor.

Files never leave your browser. Merge runs locally via FFmpeg/WebAssembly.

When merging is the right move

A few obvious cases: an interview cut into Q&A chunks that needs to be one deliverable, a screen recording that auto-split into chunks because the recorder hit a duration limit, b-roll plus the main take that should ship as a single video, or multiple speakers each recorded separately on their own machine. The browser tool now normalizes clips before joining them, so ordinary MP4 files keep playing after the first segment and retain audio in later segments.

How it works under the hood

We use FFmpeg's concat demuxer after first re-encoding each clip to a common H.264/AAC shape. That costs more time than stream-copying, but it avoids the common broken output where only the first MP4 segment plays or later audio disappears.

When you need a desktop tool instead

If your clips are very large, very long, or came from high-bitrate cameras, browser-side FFmpeg can run into memory limits. You can pre-convert one-clip-at-a-time with our WebM → MP4 converter or MOV → MP4 converter and then merge — or skip the browser memory ceiling entirely and use HandBrake, FFmpeg locally, or a video editor on your machine. For mixed-source merges at scale, desktop is faster.

Recording in chunks on purpose?

If you're recording a long session and worried about losing it all to a crash, chunked recording is sensible — but the easier path is a recorder designed for long sessions to begin with. Clipy handles long takes natively, ships you a sharable link without an upload-step round trip, and never asks for a signup on the viewer side. Use this merge tool to tidy up after the fact; use Clipy if you'd rather not need to merge.

Common questions

Why does merging fail with 'invalid data found' or weird audio?

The tool normalizes each clip before concatenating, which fixes the most common MP4 failures. If it still fails, the browser FFmpeg runtime most likely ran out of memory or hit a damaged source file.

Why is merging slower than before?

We re-encode clips to a common H.264/AAC format before joining them. That is slower than stream-copy, but it produces a playable file instead of a brittle concat that can stop after the first segment.

Can I drag clips to reorder them?

We kept the UI to up/down arrows on each clip, which is faster than full drag-and-drop on a touch device and works the same on mouse. Each click swaps a clip with its neighbor.

What's the size limit?

About 800 MB combined input — that's the WebAssembly memory ceiling we comfortably stay under. For larger merges, run FFmpeg locally or use a video editor; the math doesn't change, just the runtime.

Does the output preserve audio?

Yes. Audio is normalized to AAC and joined with the video, so later clips should remain audible in the merged MP4.

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