Add Music / Voiceover
Add background music, replace a video's audio, or record a voiceover right on your device — start offset, loop-to-fit, and volume mixing included. Your video is never re-encoded, so this stays fast.
About this tool
What you provide
- A video file (MP4, MOV or WebM)
- An audio file (MP3, M4A, WAV or OGG), or a recording from your microphone
- Mode — replace, mix or voiceover — plus start offset, loop-to-fit and volume levels
What you get
- An MP4 carrying the new audio, with the video stream copied unchanged
Limits
- The video is never re-encoded, so its quality is unchanged; the audio is encoded to AAC at 128 kbps.
- Mix mode needs the video to already have an audio track — otherwise use Replace.
- Everything runs on your device, so very large files depend on your device's memory.
How to use it
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Add your video
Drop an MP4, MOV or WebM file onto the dropzone, or tap it to choose one.
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Choose a mode
Pick Replace to swap the audio out, Mix to lay music over the existing sound, or Voiceover to narrate.
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Supply the audio
In Replace and Mix, choose a file in the "Audio file" field; in Voiceover, tap Record then Stop to capture from your microphone, or tap "Audio file" to upload instead.
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Adjust and save
Set the "Start offset (seconds)", tick "Loop audio to fill the video" in Replace or Mix, move the Video volume and Music volume sliders that Mix adds, then tap "Add Music / Voiceover" and "Save / Share".
Frequently asked questions
How do I add music or a voiceover to a video?
Upload your video and an audio file, choose music, narration, or both, then export. The audio is merged without re-encoding the video.
Does adding audio reduce my video's quality?
No, the video track is copied as-is rather than re-encoded, so its original quality is preserved.
Is this tool free and does it upload my files?
Yes, it's free to use, and the merge happens entirely on your device without uploading your video or audio.