Related tools
Why replace video audio?
Swap narration, music, or fix bad room tone without re-exporting an entire edit — useful for quick social cuts, language swaps, or dropping in a mastered mix while keeping the same picture.
Benefits
- New soundtrack: Lay in music, voiceover, or a cleaned-up mix.
- Picture unchanged: The video stream can be copied or re-wrapped depending on the pipeline; visuals stay as captured.
- Flexible output: Export MP4, WebM, or MOV when supported.
- Local processing: Designed to run in your browser without uploading your media to our servers.
- Simple flow: Two files, preview, one export button.
How this tool works
You provide a video and a replacement audio file. The tool decodes the new audio, aligns length with the video (trimming or looping in the WebCodecs-style path, or shortest stream matching in the fallback path), multiplexes with the video, and writes a new file. One video and one audio file per run.
Workflow (overview)
- Video: Load the clip.
- Audio: Load the new track.
- Preview: Confirm files and duration hints.
- Format: Choose container for export.
- Export: Mux, encode if needed, download.
Facts
Before you export, keep these in mind.
Key points
- Original audio is not recoverable from the new file — keep your source video if you need the old mix.
- Re-muxing or transcoding can still affect timestamps and compatibility; test playback on your target device.
- Very long videos need more time and memory in the browser.
- Supported codecs depend on your browser and the conversion path (primary engine vs fallback).
- Stereo vs mono and sample rate are normalized during encode to the pipeline’s AAC settings when applicable.
Best practices
Get cleaner results with less friction.
Audio and quality
- Use a mastered file at consistent loudness to avoid jumps after the swap.
- Match duration closely when you can; extreme trims can clip phrases or music unexpectedly.
- Prefer lossless or high-bitrate sources before final encode.
- Keep an unmodified video master for future changes.
- If lip-sync matters, prepare audio timed to picture in your editor first — this page is for straightforward track replacement.
Common use cases
- Quick fixes: Replace noisy camera audio with a studio take.
- Music: Drop in a licensed track for a vertical cut.
- Localization: Swap a VO track for another language.
- Social: Refresh audio on a repost without re-rendering effects.
- Archiving: Create a listening copy with commentary track.
Technical overview
The primary path reads encoded video packets, builds a new container with an AAC track synthesized from your audio buffer, and finalizes. A fallback path uses compatible fallback copy of video and AAC from your audio, with duration matched via shortest stream. All intended to stay client-side.
Process
- Load: Video and audio are read from your device into the browser.
- Decode: Audio is decoded to a buffer for timing alignment when using the advanced pipeline.
- Mux / encode: Video and new audio are combined into the selected output format.
- Download: You save the file locally.
- Privacy: Processing is intended to stay on your machine without uploading files to our servers.
Powered by browser media APIs and optimized encoding pipelines.
Frequently asked questions
Will my video quality drop?
Picture quality is preserved when the video stream is copied in the fallback path; the primary path may re-encode video depending on settings. In both cases the goal is minimal unnecessary change to the image.
What if audio is longer than the video?
The advanced pipeline trims audio to the video duration. The in-browser media engine fallback uses -shortest so output ends when the shorter stream ends.
What if audio is shorter?
The advanced pipeline can loop the audio to fill the video duration. in-browser media engine fallback still uses -shortest, which may end the file earlier — check previews and choose the path that fits your clip.
Is my data secure?
Processing is designed to run locally in the browser without uploading your video or audio to our servers.
Can I restore the old audio?
Not from the exported file. Keep your original video if you need the previous mix.
Multiple videos at once?
Process one pair of files per run; repeat as needed.
Which formats can I export?
Typically MP4, WebM, or MOV depending on support and the active conversion path.