Replace Audio
Put new music or a voice-over on a video, replacing or mixing with the original sound.
Free · No upload · 100% on your device
Replace Audio
Choose the video, or drop it here.
MP4, MOV, MKV, WebM, AVI and more · No size or length limit. Nothing is uploaded.
100% on your device
How to use Replace Audio
- Choose your video, or drop it on the page.
- Pick the settings in the side panel.
- Select “Replace audio”. The first use downloads the video engine once.
- Download the result. Your original file is left unchanged.
Private by design. Your files are processed in this browser tab and are never uploaded to KittySuite.
About Replace Audio
Choose the video first, then the new audio (any audio file, or a video whose sound you want). The picture is copied without re-encoding. The new audio is cut at the end of the video; if it is shorter, the rest of the video is silent. Mix keeps the original sound under the new one.
Processing happens in this tab with FFmpeg compiled to WebAssembly; your files are never uploaded. The first video or audio tool you use downloads the 10 MB engine once and keeps it cached for next time. Long or high-resolution videos take longer than on a desktop editor, especially on phones, where files are processed one at a time to stay within memory. Keep the tab open until the download appears.
Replace Audio: frequently asked questions
How do I add music to a video?
Choose the video first, then the audio file. Choose Replace to swap the sound, or Mix to keep the original sound under the new one.
What if the music is longer or shorter than the video?
Longer audio is cut at the end of the video. If it is shorter, the rest of the video is silent.
Can I use the sound from another video?
Yes. Choose a video as the new audio and its soundtrack is used.
Is the picture re-encoded?
No. The video picture is copied as it is.