Check Your Audiobook for ACX Compliance

A free browser-based tool that analyzes all your audiobook chapter files for ACX compliance and cross-chapter consistency. Upload every chapter at once — the tool checks RMS loudness, peak levels, and noise floor for each file, then highlights inconsistencies that could cause ACX rejection.

How to Use

1
Upload All Chapters

Drag and drop all your audiobook chapter files at once. The tool accepts MP3, WAV, FLAC, and other common formats.

2
Review Analysis

Each chapter is analyzed for ACX compliance. A sortable table shows RMS, peak, noise floor, and pass/fail status for every file.

3
Check Consistency

The deviation chart and consistency overview reveal whether your chapters have uniform loudness and noise levels.

4
Fix Issues

For chapters that fail, click "Fix in ACX Mastering" to open the auto-mastering tool and correct them.

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Verify loudness, peaks, and noise across all chapters before submitting to ACX

Drop all chapter files here or click to browse
MP3, WAV, OGG, FLAC, AAC, M4A, M4B, WMA, AIFF, OPUS, CAF ·
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RMS Consistency
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Range: —
Peak Levels
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Worst: —
Noise Floor
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Worst: —

Chapter Analysis

# File Duration RMS Peak Noise Sample Rate Channels Status

RMS Loudness by Chapter

Issues Found

    Fix in ACX Mastering
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    Features

    Full ACX Compliance Check Cross-Chapter Consistency Actionable Issue List

    FAQ

    Why does consistency matter for ACX?

    ACX reviewers check that all chapters have similar loudness, noise floor, and tone. Inconsistency between chapters (e.g., one chapter recorded in a different room) is the #1 reason audiobooks get rejected even when each chapter passes individually.

    What level of RMS variation is acceptable?

    ACX does not publish an official limit, but experienced narrators recommend keeping RMS within 2 dB across all chapters. This tool flags any chapter deviating more than 2 dB from the average.

    How many files can I upload?

    There is no limit on the number of files. Each file is analyzed individually in your browser. Processing time depends on file size and your device speed.

    Can I check files that are already mastered?

    Yes. Upload your final mastered files to verify they all pass ACX requirements before submitting. This is the last quality check before upload.

    Is this the same as the ACX Check plugin?

    The ACX Check plugin for Audacity checks one file at a time. This tool checks ALL chapters simultaneously and adds cross-chapter consistency analysis that no other tool provides.

    💡 Want us to improve this tool just for you?

    We can — and it's free! Just send us a quick message with your idea. If you'd like to discuss it in detail, leave your email and we'll get back to you. You can stay anonymous.

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    Who is this tool for?
    🎙️ Podcasters 📖 Audiobook Narrators
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