Free tool

Pass ACX on the first try.

Drop a finished chapter and instantly see whether your peak, loudness and noise floor meet Audible's specs — with a plain-English fix for anything that's off. Runs entirely in your browser; your audio stays on your device.

Try it

Check a chapter against ACX specs

The fastest way to catch a rejection before you submit — no plugins, no signup.

Drop your chapter here

MP3, WAV, M4A or FLAC — up to 25 MB. We'll measure it against the Audible spec.

How it works

Your audio never leaves your device

The checker decodes your file and measures peak, RMS loudness and the quietest half-second of room tone — all on your machine, no server round trip.

Step 1

Drop the chapter

MP3, WAV, M4A or FLAC — up to 25 MB.

Step 2

We measure it

Peak, RMS loudness and noise floor are computed in your browser.

Step 3

Read the checklist

Each spec shows pass or fail with the number and a fix tip.

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Producing a whole audiobook?

Open AudioPod's Audiobook Studio to narrate, master to ACX specs, add chapter credits, and export an Audible-ready package — all on one free account.

Open Audiobook Studio