Merge Video with Audio
Combine a video file with an audio track. Max file size: 250MB
Merge Video + Audio
Drop video files here or
Maximum file size: 250MB • Files: 0 / 1
Accepted format: video files
Drop audio files here or
Maximum file size: 50MB • Files: 0 / 1
Accepted format: audio files
Download Merged Video
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Upload and merge video and audio files to see them appear here for download.
Combine a video file with a separate audio track in your browser to replace or add sound to any video. The merge tool supports sync offset adjustment, audio replacement, and common format combinations — all processed locally with FFmpeg-WASM for full privacy.
Merge Video and Audio Files Online — Replace Audio in Browser
Adding or replacing a video's audio track is a common task for content creators, video producers, and educators. Whether you want to dub a video with a new language soundtrack, add background music to a silent clip, or replace poor-quality recorded audio with a professionally mixed track, this browser-based merge tool handles the job entirely in your browser using FFmpeg-WASM.
The tool accepts separate video and audio files and combines them into a single output. You can replace the video's existing audio track completely or mix the new audio on top. A sync offset control lets you shift the audio track forward or backward in time relative to the video, ensuring your dubbed voiceover or background track aligns perfectly with the action on screen.
Output compatibility is broad — the tool supports MP4, WebM, MOV, and MKV containers. When replacing audio, the video stream is copied losslessly (no re-encoding) to preserve original video quality. The audio is re-encoded to the target container's preferred codec (AAC for MP4, Opus for WebM). Because all processing happens locally via FFmpeg-WASM, your video and audio files never leave your device.
Replacing Video Audio with a New Soundtrack
Swap a video's original audio with a clean music track, professional voiceover, or dubbed soundtrack for localization and content repurposing.
Adding Background Music to Silent Video
Combine a muted screen recording or silent video clip with an audio file to add a background soundtrack before sharing or publishing.
Dubbing for Localization
Attach a translated voiceover audio file to an existing video to create a localized version for a different language audience.
- 1
Upload the Video File
Select your source video (MP4, WebM, MOV, or MKV). The video stream will be copied without re-encoding to preserve original video quality.
- 2
Upload the Audio File
Upload the audio track you want to merge into the video. Supported formats include MP3, AAC, WAV, OGG, and FLAC.
- 3
Set Sync Offset (Optional)
If the audio needs to start later or earlier than the video, enter a positive or negative offset in seconds. This aligns the audio track with any specific point in the video.
- 4
Merge and Download
Click Merge to combine the streams using FFmpeg-WASM. Download the resulting video file with the new audio track embedded.
Audio Sync Offset Control
Shift the audio track forward or backward by any number of seconds to precisely align a voiceover, music track, or dub with the video content.
Lossless Video Stream Copy
The video track is merged without re-encoding, preserving the original video quality, resolution, bitrate, and codec.
Multiple Audio Format Support
Accepts MP3, AAC, WAV, OGG, and FLAC audio files as input, making it easy to work with audio from any source.
Private Browser-Based Processing
FFmpeg-WASM handles all stream merging locally in your browser. Neither the video nor audio file is ever uploaded to a server.
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