Video Audio Adder Add background music or audio tracks to your videos.
Video Audio Adder
Add background music or audio tracks to your videos.
Upload Video & Audio
Upload your video file and the audio file to add.
Configure
Set audio volume and choose to replace or mix with existing audio.
Merge & Download
Click Merge and download your video with the new audio.
What Is Video Audio Adder?
The Video Audio Adder is a free browser-based tool that adds background music, voiceover, or any audio track to your videos. Upload both a video and an audio file, and the tool combines them into a single video with the new audio track. Choose to replace the original audio entirely or mix the new audio alongside it with adjustable volume levels. It's perfect for adding background music to silent videos, overlaying narration, or replacing unwanted audio. The tool uses Web Audio API for mixing and MediaRecorder for output. All processing happens locally in your browser.
Why Use Video Audio Adder?
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Add music, voiceover, or sound effects to any video
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Replace or mix with existing audio
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Adjustable volume balance between tracks
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No uploads — private processing on your device
Common Use Cases
Background Music
Add music tracks to silent or quiet videos.
Voiceover
Overlay narration or commentary on video content.
Audio Replacement
Replace poor-quality original audio with a clean recording.
Sound Design
Add sound effects or ambient audio to video clips.
Technical Guide
The Video Audio Adder uses the Web Audio API to mix multiple audio sources. The video's original audio is captured via createMediaElementSource(), and the new audio file is decoded into an AudioBuffer via decodeAudioData(). Both sources are routed through separate GainNodes for volume control, then mixed through a channel merger or directly to a MediaStreamDestination. In replace mode, only the new audio source is connected. In mix mode, both sources are connected with adjustable gain levels. The combined audio stream is merged with the canvas video stream and fed to MediaRecorder. If the audio is shorter than the video, it can loop or pad with silence. If longer, it's trimmed to match the video duration.
Tips & Best Practices
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1Match audio length to video length for best results
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2Use "Replace" mode to completely swap the audio track
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3Adjust volume balance to prevent one track from overpowering the other
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4For best mixing, use high-quality audio files
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🎬 Video ToolsFrequently Asked Questions
Q Can I keep the original audio too?
Q What if the audio is longer than the video?
Q What audio formats are supported?
Q Is my video kept private when adding audio?
Q Can I adjust the timing of the added audio?
About This Tool
Video Audio Adder is a free online tool by FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration or installation required.