Put music, a voice-over or a new soundtrack on any video. Replace the original sound or mix both, choose where the audio starts, set the volumes and add fade-in and fade-out, preview it live, then download the new video. Everything happens in your browser.
Your video appears here. Press play on it to preview the new sound.
Timeline
Sound of the new video
Video output settings
Choose a video and an audio file to begin.
Starting…
The video is recorded in real time. Keep this tab open and visible.
Your video with the new sound is ready
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How to use the Add Audio to Video
Open your video in the first box.
Add the audio: drop an MP3, WAV, M4A, OGG or FLAC file in the second box.
Choose Replace or Mix, then set the volumes, where the audio starts, fades and looping. The timeline shows how it lines up.
Press play on the video to hear the result live and adjust until it sounds right.
Press Create video, wait while it records in real time, then download the new file.
Replace or mix: which to choose
You want to…
Mode
Suggested volumes
Put music on a silent clip, a screen recording or a time-lapse
Replace original
New audio 100%
Swap a noisy soundtrack for a clean voice-over
Replace original
New audio 100%
Add background music under people talking
Mix with original
Original 100%, music 25–40%
Add a voice-over on top of ambient sound
Mix with original
Original 30–50%, voice 100–130%
Add a sound effect at one moment
Mix with original
Original 100%, effect 100%, set Start in video
Volumes above 100% amplify the sound. If the result distorts, lower the volumes: when two loud sources are mixed, their sum can exceed the maximum level. A change of 50% is about −6 dB; 200% is about +6 dB.
How the timing works
The new audio is placed on the video's timeline. Start in video is the moment the audio begins; Skip start of audio cuts that many seconds from the beginning of the audio file. The audio then plays until the audio file ends or the video ends, whichever comes first, so the new video always has exactly the length of the original. With Loop on, the audio repeats from the skip point until the video ends.
The fade-in starts where the audio starts. The fade-out ends where the audio ends: at the end of the audio file, or at the end of the video when the audio is longer. Fades are linear changes in volume over the number of seconds you set.
Tips for good results
Use the live preview: play the video, then adjust volumes and timing while you listen. The timeline shows the volume curve as a line over the audio waveform.
To start the music on a specific event, pause the video at that frame and press Start audio at current video time.
Keep the original resolution for the best picture; choose 720p for smaller files to share in chat apps.
Recording happens in real time, so a 3 minute video takes about 3 minutes. Keep the tab visible so no frames are dropped.
Frequently asked questions
How do I add music to a video without losing the original sound?
Choose Mix with original sound. Both play together, and you can lower the music (for example to 30 to 50%) so voices in the video stay clear, or lower the original sound to make the music stand out.
Can I start the music later in the video?
Yes. Set Start in video to the second where the audio should begin, or drag the audio on the timeline. Use Skip start of audio to begin the song at its chorus or to cut a silent intro.
What happens if the audio is longer or shorter than the video?
The new video always keeps the length of the original video. Longer audio is cut at the end of the video, and the fade-out is applied there. Shorter audio stops when it ends, or repeats from the skip point if Loop audio is on.
Why does creating the video take as long as the video itself?
Browsers have no built-in video editor, so the tool plays the video once in the background, draws each frame and records it together with the new sound using the browser's MediaRecorder. That runs in real time: a 2 minute video takes about 2 minutes. Keep the tab visible while it works.
Which formats do I get?
Chrome, Edge and Safari can create MP4 files (H.264 video with AAC or Opus audio), and Firefox creates WebM (VP8 or VP9 with Opus). Both play in browsers, VLC and most phones; MP4 is the safer choice for sharing and social media.
Is it really private?
Yes. Your video and audio files are opened with the browser's own media decoder and recorded on your device. Nothing is uploaded to a server, and the result has no watermark.