Merge audio files into one
Add your MP3 or M4A files, put them in order and join them into one track. Listen to the result before you download it; nothing is re-encoded or uploaded.
Runs on your device · 0 bytes uploaded
Drag files to reorder, or use the arrows.
How to merge Audio
- Add two or more MP3 files, or two or more M4A files.
- Put them in order with the ↑ and ↓ buttons.
- Click “Merge audio”, listen to the result and download it.
Private by design — and you can check
Your files are never uploaded, because there is nowhere to upload them to.
- No upload step existsFiles are read and written inside this browser tab. There is no server that could receive them.
- The browser enforces itThis page’s Content Security Policy only allows connections back to this site, which serves nothing but the app itself.
- See for yourselfOpen developer tools, watch the Network tab and run a job: no request carries your document.
- Open sourceEvery line is on GitHub, built on qpdf, pdf.js & pdf-lib.
Frequently asked questions
Are my files uploaded anywhere?
No. Fizzdoc does the work inside your browser tab, using open-source engines compiled to WebAssembly and JavaScript. Your file is read from your device, processed locally, and the result is saved straight back to your device. You can check this yourself: open your browser’s developer tools, go to the Network tab, and run a job — no request carries your file.
Can I merge an MP3 with an M4A?
Not yet. Join files of one type at a time. Converting between formats is planned, and help is welcome on GitHub.
Why does it say my files use different audio settings?
Files recorded at different sample rates (for example 44.1 kHz and 48 kHz) cannot be joined without re-encoding, which Fizzdoc does not do yet. Files from the same phone, app or album almost always match.
Is Fizzdoc free?
Yes. There is no sign-up, no watermark and no daily limit. Fizzdoc is open source under the Apache-2.0 license.
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