Batch Add Audio to Video
Drop in your soundtrack, queue every clip, and click run. The browser handles the mix locally—no uploads—and you can either download the finished videos or send them all into one folder for quick handoff.
No audio selected yet.
No videos queued yet.
3-5% works well for background music.
Mix strategy
Output folder (optional)
Leave this empty to download files through the browser. Pick a folder if you want every export written to the same destination automatically.
File System Access API is only available in Chromium-based browsers.
FFmpeg status
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FFmpeg log
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How the workflow works
Pick a soundtrack
Upload or pick a WAV/MP3 once, then set the mix volume.
Queue your videos
Use the system video picker as often as you need to build a queue of MP4/MOV/WEBM clips.
Export anywhere
Send exports straight to your Downloads or grant local folder access so each render lands exactly where you want it.
Why editors use this tool
No server uploads
Files stay in browser memory. It mirrors the behavior of your local shell scripts (like merge-video-audio.sh) but wrapped in a friendly UI.
Folder-aware saving
Grant Chrome/Edge access once, then drop every new render into the same local exports directory for instant handoff.
FFmpeg mixing logic
We ported the same amix pipeline from your bash scripts - looped music, custom volume, optional video-audio blend, and mp4/webm aware codecs.
Batch-proof feedback
Progress bars, FFmpeg logs, and per-file status help you spot failures quickly and download only what you need.
FAQ
Can it handle short-form batches for TikTok, Reels, or Shorts?
Yes. Load the 15-60 second vertical clips you cut for TikTok, Instagram Reels, or YouTube Shorts, pick one trending track, and the tool loops it across every video. Because everything runs locally, you can test multiple music vibes before uploading to each platform's scheduler.
What about long-form videos for YouTube or LinkedIn?
Editors use this to add subtle background beds to 10-minute tutorials, webinars, or LinkedIn thought-leadership clips. The original dialog stays intact (mix mode) while the music sits at a low 3-5% volume, so you don't have to remix audio in Premiere or Final Cut every time.
I run a social agency - can I keep files organized per client?
Use the output folder picker to point every finished file at a /Clients/Acme/Delivered directory on your machine. That way TikTok, Facebook, and paid ads variations stay grouped without manual moves.
Will this re-encode my video or hurt quality?
Most MP4/MOV/M4V files keep their original video stream - you only get a new audio track. WEBM clips keep VP8/VP9 with fresh Opus audio. If a codec mismatch appears, the tool automatically re-encodes to MP4/H.264 and flags the file in the status column so you know it changed.
Can I run different songs for different campaigns?
Each batch shares the same soundtrack, which keeps brand sound consistent. If you need a second vibe for a separate Instagram or Snapchat campaign, simply rerun the tool with a new audio file and a different set of videos.
Does it work with iPhone MOV files and 4K exports?
Yes. MOV and 4K MP4 clips from iPhone, Android, mirrorless, or DSLR cameras are supported. The main limitation is RAM inside your browser, so process very large shoots in waves of a few clips at a time.
Will captions, metadata, and aspect ratio stay intact?
The video stream is copied whenever possible, so burn-in captions, resolution, frame rate, and color profiles stay untouched. Only the audio track changes, and the new file inherits the original aspect ratio for TikTok, Twitter, or YouTube uploads.
Can I preview the mix before running 50 clips?
A quick trick: add one test video first, confirm the 3-5 percent music level you like, then queue the rest. You can also duplicate the tab to run another batch with a louder mix for platforms like Facebook that compress audio more.
Does it run on Windows, macOS, or ChromeOS?
Any desktop that can run a Chromium-based browser (Chrome, Edge, Brave, Arc) works. The processing happens inside the tab, so there is nothing to install beyond opening the page.
Can I stay offline?
After the initial FFmpeg.wasm download (about 30 MB), you can keep the tab open and work without an internet connection. Everything else uses your local CPU, so it is safe to run on shoots with limited Wi-Fi.
How do I share the finished files with clients?
Use the "Choose output folder" option to save exports into a dedicated local directory (for example /Projects/Client/Delivered). Every new render gets the suffix "-with-music" so you can copy the final folder to whatever delivery method you prefer.
What if I need to revert to the original audio?
The tool never overwrites your sources. It creates copies with the "-with-music" naming pattern, so you can discard or archive them anytime while keeping the raw footage untouched.
Does the output work for podcasts, webinars, or long LinkedIn videos?
Absolutely. Many teams add low-volume beds to 20-minute webinars or podcast highlights before uploading to YouTube, LinkedIn, or Vimeo. Just keep the volume slider near 3 percent so voice tracks stay clear.
Can I keep track of which clips succeeded?
Yes. Each video in the queue shows a badge (pending, processing, success, or error) plus a status note. You can filter by removing finished results or re-run only the items that reported an error.
What happens if I mix super loud music?
The slider goes up to 100 percent, but for social channels like TikTok, Facebook, or X, keeping the value under 10 percent prevents clipping after the platform re-encodes your upload. You can always rerun the batch with a softer level and overwrite the exported files.