Replace Audio — MP4 Online

Mux a new audio track with MP4 video in your browser — previews and length matching.

Choose a compatible export format. Input is preserved when supported — private processing. No registration.

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Select video file

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Select audio file

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MP4 Replace Audio

Swap the audio track on MP4 in your browser. Free, no upload.

MP4 (often H.264 + AAC) is the default for sharing. This page highlights MP4 sources: replace the soundtrack, then export — usually MP4 for the widest playback.

When to use MP4 Replace Audio vs other formats

Use when your master is MP4. WebM is web-first; MOV suits some Apple editors. You can still export MP4, WebM, or MOV after processing.

Compatibility

Exported MP4 (H.264) plays broadly on phones, TVs, and browsers.

Quality considerations

Start from clean audio; level-match to avoid jumps after the swap.

Example use cases

  • Swap VO on phone MP4.
  • Music under a vertical reel.
  • Fix noisy room tone quickly.

Best practices

  • Keep an original without the swap.
  • Preview duration vs video.
  • Export MP4 when unsure about devices.

Common use cases

  • SocialNew track on short MP4.
  • FixesCleaner audio on clips.
  • LocalizationAlternate language mix.
  • DeliveryClient cut with final mix.
  • ArchiveCommentary version beside master.

Powered by browser video APIs and optimized encoding pipelines.

All video formats (MP4, WebM, MOV) · MP4, WebM, MOV

MP4 Replace Audio — Free Online