Add Audio to Video Online — Free Background Music Adder
Replace or add an audio track to any video. Upload your video and audio separately — download an MP4 with the new sound. No software, no sign-up needed.
1 · Video file
Drag & drop your file here, or
Max 100 MB • Max 10 min duration • Max 1080p
2 · Audio file
Drag & drop your file here, or
Max 100 MB • Max 10 min duration • Max 1080p
Output: MP4 (H.264 + AAC) — original audio removed, new audio track added. Output length = shorter of the two files.
How to Add Audio to a Video Online — 3 Steps
Upload your video and audio separately — our server replaces the audio track and gives you back a clean MP4 in seconds.
Upload your video
Select any video file — MP4, WebM, MKV, MOV, AVI, FLV, or WMV — up to 100 MB. The original audio track will be replaced.
Upload the replacement audio
Select any audio file — MP3, WAV, FLAC, AAC, OGG, M4A, or OPUS. This audio will become the new soundtrack of your video.
Download the combined MP4
Click Add audio to video and download the result. The output is MP4 H.264 — compatible with YouTube, TikTok, Instagram, and every major video editor.
When to Add or Replace Audio in a Video
The most common reasons creators need to swap or add audio to their footage.
Frequently Asked Questions
Does this replace or mix the audio?
It replaces the audio. The original audio track is removed and the new audio track takes its place entirely. If you need to mix (overlay) the new audio with the original, use a desktop editor like DaVinci Resolve, Kdenlive, or CapCut, which supports multi-track mixing.
What if the audio is shorter than the video?
The output is trimmed to the length of the shorter stream. If your video is 3 minutes but your audio is only 1 minute, the output video will be 1 minute long. To fill the full video length, either use longer audio or loop the audio in an audio editor first.
What if the audio is longer than the video?
The audio is automatically cut at the end of the video. Only the portion of the audio that aligns with the video duration is included in the output.
Can I add audio to a silent video that has no audio track?
Yes. If the video has no existing audio track, the new audio is added as the first and only audio track. The result is identical — you still get a clean MP4 with the new audio.
What formats are supported?
Video: MP4, WebM, MKV, MOV, AVI, FLV, WMV. Audio: MP3, WAV, FLAC, AAC, OGG, M4A, OPUS. Each file can be up to 100 MB. The output is always MP4 H.264 + AAC.
Is this tool completely free?
Yes — no account, no watermarks, no subscription. Upload your files and download the result.
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