Swap a video's sound for another track, keeping every frame of the picture as it was
Processed in your browser. Nothing is uploaded. Updated on 24 Oct 2026.Replacing the sound of a video should not cost any picture quality, and here it costs none: the video frames are copied into the new file exactly as they were, so a 4K clip stays 4K and a 2 GB file is done in well under a minute. The old soundtrack is dropped, the new one is lined up where you put it, and anything longer than the video is cut at its last frame.
Press Choose video and pick the clip whose sound you want to swap.
Press Choose audio and pick the new track; Original sound is already at 0%, so the old soundtrack is left out.
Drag the Start the audio at slider, or type an offset, to line the new track up; anything past the last frame is cut.
Press Save the video with this sound to write the new MP4 with every frame copied.
This page puts a new sound track on a video: a song, a voice-over, a cleaner microphone recording, or nothing at all. It was built for the job of finishing AI-generated clips for YouTube, where the picture is final and only the sound changes, and for that job the one thing that must not happen is the picture getting worse.
So the picture is never re-encoded. Every video frame is read from your file and written into the new one byte for byte, which is why a 4K or 8K video keeps every pixel and why a long file finishes quickly: nothing is decoded, nothing is compressed a second time. The quality check behind this page compares the frames of the result with the frames of the original and requires them to be identical.
How the sound is written. When the new audio is AAC in an M4A or MP4 file and is heard exactly as it is from the first frame, its frames are copied too, and the whole file is lossless. Anything else is mixed and encoded to AAC at 256 kbps, which is transparent to the ear; the page says which, and why, before you press the button.
The rest of the article, and all 6 questions about Add Audio to Video, are on the Add Audio to Video page.
Drop the video and the music file here and save. The video frames are copied into the new file exactly as they were, not re-encoded, so a 1080p or 4K video keeps every pixel. Only the sound track is new.
Drop the video and the new audio, leave "Original sound" at 0%, and save. The old sound track is dropped and the new one takes its place, lined up where you put it and cut at the video's last frame if it is longer.
Yes. Set Original sound above 0% and the video's own sound stays, with the new audio mixed in at its own volume. For background music under speech, 100% original and 20 to 30% music is a common starting point; a fade-out at the end avoids stopping mid-note.
MP3, M4A, AAC, WAV, OGG, Opus and FLAC, and the sound of another MP4 or MOV. The video must be MP4, MOV or M4V. The result is always an MP4 that plays everywhere and uploads to YouTube as it is.
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Same job, other tools: Add Logo to Video – Put your PNG logo on a video, bottom right, sized and placed by dragging · Change Video Speed – Speed up a video or make slow motion, from 0.25x to 4x, with the sound kept in pitch · Compress Video – Make a video file smaller at a lower bitrate or resolution, right in your browser · GIF to MP4 Converter – Turn an animated GIF into a much smaller MP4 video, each frame kept for its own delay · Video to GIF – Cut up to 15 seconds out of a video and save it as a looping animated GIF.
On the related tools: Combine AI Video Clips – Join Google Flow, Veo or other AI clips into one video in story order.