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AudioMaster LUFS

Master audio to a loudness target using FFmpeg's loudnorm filter in a measured two-pass process: the first pass measures your audio's integrated loudness, true peak, and loudness range; the second pass normalizes using those measurements; then the finished file is re-measured — so the result you get back is a measured value, not an estimate. It runs entirely on your own computer: no uploads, no account.

Measured output — a real run

Loudness targets

• Spotify — −14 LUFS — Spotify and most music streaming.
• YouTube — −14 LUFS — YouTube uploads.
• Apple — −16 LUFS — Apple Music / Apple Podcasts loudness.
• Podcast — −16 LUFS — spoken-word podcast distribution.
• Custom — any value from −36 to −5 LUFS; you set the number.

Every master holds a true-peak ceiling of −1 dBTP. Output is 16-bit PCM WAV at 48 kHz.

Formats and limits

• Input — WAV, MP3, M4A, FLAC, OGG (AAC also accepted).
• Limits — up to 200 MB per file and up to 30 minutes long.
• Optional web UI — the download also includes a local app.py interface; the command-line tool needs nothing beyond Python + FFmpeg.

How to use it

1. Download and unzip the free ZIP above, and confirm ffmpeg -version works in a terminal.
2. Master a test file first — python cli.py my-track.mp3 my-track-mastered.wav --target spotify — and listen to the result before processing a full release.
3. Check the printed measurements — the JSON summary reports the measured output loudness and true peak.
4. Listen before you ship — loudness-correct is not the same as sounds-right; if the mix is harsh or muddy, fix the mix and re-master.

The honest limits

AudioMaster normalizes loudness to the target you select; it does not guarantee acceptance by any streaming platform, broadcaster, or distributor — platforms apply their own measurement and playback normalization, and their policies change. Master from the best-quality source you have: loudness processing cannot restore quality lost earlier. Full tips and troubleshooting are in the guide.

More free tools: TextClean Transformer cleans pasted text right in your browser, and Accessibility Content QA scores static HTML for accessibility issues, offline. All three are also in the free tools section on the home page.