How to Add Background Music to a Video Online
Adding audio to a video — background music, a voiceover, sound effects, or a royalty-free music track — transforms raw footage into polished content. This guide explains how to add audio to any video online, when to replace vs layer audio, and where to find royalty-free music that will not get your content flagged.
What This Tool Does: Audio Replacement
The Add Audio to Video tool replaces the original video audio track with your new audio file. The original audio is discarded; the new audio becomes the complete audio track of the output video. Use this when you have footage with unwanted audio (background noise, wind, unlicensed music) and a clean replacement (royalty-free music, a voiceover recording).
If you want to mix the original audio with new audio — for example, keep a presenter's voice while adding background music underneath — you need to mix the audio tracks first in Audacity (free) or GarageBand, then add the mixed result to the video using this tool.
- Mute the video first with the Mute Video tool, then add your replacement audio here for a clean two-step workflow
- Record your voiceover as an MP3 or WAV, then use this tool to attach it to the silent video
- The audio file does not need to be the same length as the video — it is trimmed or left silent to match
Finding Royalty-Free Music
For YouTube and social media, you need music that is in the public domain, licensed Creative Commons, or explicitly royalty-free for commercial use. Using copyrighted music — even for a few seconds — triggers automated Content ID and can result in your video being muted, taken down, or monetised by the rights holder.
The best free sources: YouTube Audio Library (free, most tracks need no attribution), Pixabay Music (CC0 — completely free, no attribution required), and Freesound (mixed licensing — check each track individually). For paid options with clearer licensing: Epidemic Sound and Artlist are the industry standards for content creators.
- YouTube Audio Library — best free source for YouTube creators; filter by mood, genre, and attribution requirements
- Pixabay Music — CC0 licence means zero restrictions, zero attribution required
- Epidemic Sound — best paid option; flat monthly fee covers all platforms including YouTube, Instagram, TikTok
- Never use a popular song, even for 5 seconds — Content ID detection is immediate and automatic
How to Add Audio to a Video Using MediaFormatter
Go to the Add Audio to Video tool, upload your video file (MP4, MOV, MKV, WebM, or AVI, up to 500 MB) and your audio file (MP3, WAV, FLAC, AAC, or OGG, up to 100 MB). Confirm you own both files and click Combine. The output is an MP4 with the original video stream and your new audio track.
Processing time is fast because the video stream is copied without re-encoding — only the audio track changes. A 200 MB video typically completes in under 30 seconds.