🎬

Video Audio Merger

Upload a video file and a separate audio file — merge them into one MP4 instantly. Runs 100% in your browser, nothing uploaded to any server.

🔒 100% Private — Files never leave your device. Powered by FFmpeg.wasm (WebAssembly).
  • First merge loads the FFmpeg engine (~30 MB, cached by your browser after that)
  • Large files may take 1–2 minutes depending on your device
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Video File
MP4 · MKV · MOV · AVI · WebM
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Audio File
MP3 · M4A · AAC · WAV · OGG
Loading FFmpeg…
💡 Tips
  • If the video is longer than the audio, it stops at the audio end
  • If audio is longer, it's trimmed to match video length
  • Original audio in the video is replaced

Frequently Asked Questions

Does this upload my files to a server?

No. Everything happens in your browser using WebAssembly. Your files are processed locally on your device and never sent anywhere.

What formats are supported?

Video: MP4, MOV, MKV, AVI, WebM. Audio: MP3, M4A, AAC, WAV, OGG, FLAC. The output is always MP4 (H.264 + AAC), which plays everywhere.

How long does merging take?

For a 5-minute 720p video with an MP3 it typically takes 10–30 seconds on a modern device. The first use downloads ~25 MB of FFmpeg (cached after that).

Is there a file size limit?

No hard limit, but processing happens in your device's RAM. Files over 500 MB may be slow or fail on low-memory devices. Best results under 200 MB.

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