Mix audio with a video in your browser. Your files are never uploaded.
1. Choose a video
Click or drop one video
2. Choose music
Click or drop one audio file
The preview keeps a separate audio player synchronized with the video so you can test the music start time and volume. During export, FFmpeg WebAssembly detects the original audio stream, loops or trims the music to the video length, and creates the final MP4.
Start around 60–70% music volume when keeping speech or ambient sound, then lower it if voices become hard to hear. Move the music start time past an intro when the opening needs to stay quiet.
No. FFmpeg WebAssembly reads and processes both files locally in your browser.
Yes. Leave the original-audio option on. The tool detects an audio stream during export and mixes it with your music when present.
The song loops from its beginning and the final audio is trimmed to the video duration.
The download is an MP4 with H.264 video, yuv420p pixel format, AAC audio, and fast-start metadata.
Browser processing holds media and encoder data in memory. Use smaller files if your device runs low on memory.
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