Everything happens in your browser — your files are never uploaded anywhere.
The new audio is mixed with the video's existing sound. To replace the sound entirely, use the Remove audio tool first.
Start together — audio starts at the beginning of the video and stops when it ends or the video ends, whichever comes first.
End together — audio is delayed so it finishes exactly when the video does. Only shown when audio is shorter than the video.
The output keeps the video's original format and quality — only the audio track is changed.
You can also drop a static image (JPG, PNG, WebP) instead of a video. The image will be held for the full duration of the audio and exported as an MP4 — useful for turning a podcast or song into a shareable video.
Common issues
"Your browser does not support the required features" — On Android, refreshing the page usually fixes it. On iOS, the tool now uses a single-threaded fallback that should work — if you still see this error, try refreshing.
Image + audio downloads with no sound — Can happen on some phones in Fast mode. Use the tool again with the muted video as input, or switch to Phone-safe mode which always includes audio.
Image + audio on iPhone/iPad — Not supported on iOS due to browser encoding limitations. The image option is hidden on iPhone/iPad. Use a desktop or Android device to combine a static image with audio.