Understanding ACX’s Requirements for Audiobook Cover Art and Metadata

Creating an audiobook for ACX (Audiobook Creation Exchange) involves meticulous attention to cover art and metadata specifications. These requirements are not arbitrary—they directly affect whether your title passes quality assurance, appears professional, and gets discovered on platforms like Audible, Amazon, and iTunes. Every year, thousands of submissions face rejection due to preventable errors: wrong image dimensions, mismatched metadata fields, or promotional text on covers. This comprehensive guide explains every specification in depth, provides actionable advice from industry professionals, and links to official resources. By mastering these details, you will streamline your production process, reduce revision cycles, and maximize your audiobook’s visibility from day one.

ACX Cover Art Requirements

Your audiobook cover is the first thing listeners see—it must attract attention at thumbnail size and convey genre, tone, and professionalism. ACX enforces strict technical specs to ensure consistent display across devices. Beyond compliance, your cover should compel a click. Below we dissect each requirement, explain its purpose, and offer design strategies.

Size and Resolution

The image must be exactly 2400 x 2400 pixels at a minimum, with a maximum of 3000 x 3000 pixels. This square aspect ratio ensures uniform display on all listing pages. Why 2400 pixels? That resolution supports high-density retina screens found on modern phones and tablets. Using smaller files (e.g., 1600px) will result in pixelation when scaled up and immediate rejection. Always work at 300 DPI or greater; the DPI value itself doesn’t matter to ACX’s validation, but it indicates professional preparation. If you resize a lower-resolution image, it will look blurry. Start with a high-quality source file. For designers: export at 2400x2400 px, 300 DPI, RGB, JPEG quality 10–12 (or TIFF uncompressed). Avoid any lossy compression that introduces artifacts.

File Format and Color Space

ACX accepts only JPEG or TIFF files. JPEG is preferred for smaller file size; TIFF is lossless but larger—use it if you need absolute fidelity as an intermediate file. The color mode must be RGB. Print designers often work in CMYK. If your cover was created for a print edition, convert it to RGB using software like Adobe Photoshop, GIMP, or Affinity Photo. Note that conversion can cause color shifts—test the result on multiple screens. Also, ensure the file is flattened (no layers) and that any embedded color profiles (e.g., sRGB IEC61966-2.1) are intact. ACX’s validation tool will reject incorrect color spaces.

Design and Readability at Thumbnail Size

Your cover must be clear and legible when displayed as small as 90 x 90 pixels. On mobile app shelves and search results, tiny fonts or thin strokes become unreadable. Use bold, sans-serif fonts for the title and author name. Ensure high contrast—dark text on a light background or vice versa. Avoid gradients with low contrast between text and background area. Test your cover by shrinking a preview: can you still read every word? Also check how it looks in grayscale (some devices have accessibility settings). A common mistake is using artistic effects that obscure the title. Remember, the cover serves as signage for your book.

Content and Text Restrictions

Only the book title and author name are mandatory (plus optional subtitle and series name). Do not include promotional phrases like “Winner of…”, “Now a Major Motion Picture”, website URLs, barcodes, prices, or “Read by…” text. Award logos are allowed only if subtle and relevant—but generally less is more. ACX reviews covers manually, and violations cause rejection. Even a small tagline can trigger denial. If you have a print cover with such elements, create a separate audiobook-only version. For series, include the series name and number (e.g., “The Expanse, Book 1”) either in the title area or as part of the subtitle—just ensure it matches the metadata.

Additional Cover Best Practices

  • Bleed and safe zones: Keep all critical elements at least 0.125 inches (about 37px) from the edges to avoid cropping on different devices. Some platforms may subtly crop covers.
  • Professional design investment: Avoid clip art, low-resolution stock photos, or stretched images. Hire a designer who specializes in book covers or use reputable services like SelfPubBookCovers or 100 Covers. Share the ACX specs with them upfront.
  • Consistency with print: If you have a print edition, the audiobook cover can be identical, but ensure the file meets the 2400px minimum and RGB. Sometimes print covers are at 300 DPI but smaller pixel dimensions—you’ll need to upscale using vector or high-res source.
  • Test on devices: Preview your cover on Audible’s mobile app, Amazon product pages, and iTunes before submission. Look for cropping, color shifts, and readability.
  • Format-specific adjustments: On iTunes, your cover appears circular in some views—ensure the title and author aren’t cut off at the edges.

For the official ACX cover art policy, visit ACX Cover Art Requirements.

Metadata Requirements for Audiobooks

Metadata is the bloodstream of discoverability. Every field—from title to keywords—feeds search engines, recommendation algorithms, and catalog systems. Incomplete or mismatched metadata leads to low visibility, no recommendations, and even rejection. The following sections detail each element and how to optimize it.

Key Metadata Elements

  • Title: Must match the cover exactly, including subtitle, series info, and edition. Avoid all caps unless it’s a branding choice. Use standard title case. For series, you can enter the series name and number in a dedicated series field (if available) or append it to the title (e.g., “Leviathan Wakes: The Expanse, Book 1”).
  • Author: The primary creator of the underlying work. Use the full name as it appears on covers across all platforms. Pen names are fine—just ensure consistency. For co-authors, list all using the ACX multi-author field, but check that the order matches marketing materials.
  • Narrator(s): List the primary narrator first. ACX allows up to 20 narrator fields. Spell the name exactly as the narrator uses professionally. For multi-cast productions, list each narrator; many listeners search by narrator name.
  • Genre and Category: Choose up to two genres and one category. Be as specific as possible—e.g., “Mystery > Historical Mystery” rather than just “Fiction.” Research best-selling books in your niche to see which categories they use. Misclassification hurts discoverability.
  • Description (Summary): Write a compelling, spoiler-free blurb of 200–1000 characters. Start with a hook, describe the premise, and end with a call to action like “Listen today.” Include relevant keywords naturally but avoid spammy repetition. The first 200 characters often appear in truncated lists, so front-load the most important information.
  • Language: Select the primary language of narration. For bilingual works, choose the dominant language. ACX supports many languages; ensure metadata matches the audio.
  • Keywords: Add up to 7 keywords or phrases. Think like a listener: what would they type into a search bar? Use tools like Amazon’s autocomplete, KDP keyword research, or Keyword Tool to find high-volume, low-competition terms. Avoid repeating the title or author’s name. Examples: “gritty detective noir,” “romantic comedy 2025,” “space opera series.”
  • ISBN/ASIN: If you have an audiobook-specific ISBN, enter it. Otherwise ACX assigns an ASIN automatically. Never use the print edition ISBN—that will cause errors across platforms.
  • Audible and iTunes categories: ACX allows separate category selections for Audible and iTunes distribution. Optimize each: Apple’s categories may differ from Audible’s, so leverage the best niches for each store.
  • Narrator Bio (optional but recommended): Including a short narrator bio adds credibility and helps listeners connect. Keep it 2-3 sentences covering experience and accolades.

Metadata Formatting Tips

  • Capitalization: Use standard title case for title, author, narrator. All caps or all lowercase is rarely appropriate—unless it’s a deliberate brand (e.g., “THE GIRL ON THE TRAIN” is published in all caps, but that’s an exception).
  • Abbreviations: Spell out uncommon acronyms on first use in the description (e.g., “Central Intelligence Agency (CIA)”). For well-known ones like FBI, it’s fine.
  • Series information: Enter the series name and number in the dedicated fields if ACX provides them. Otherwise, incorporate into the title field (e.g., “Book Title (Series Name, Book X)”). Ensure consistency with the cover.
  • Multiple authors/narrators: Use the exact field format—typically “and” or commas. Check ACX’s interface for the correct delimiter.
  • Unicode characters: Avoid special characters like em dashes, smart quotes, or accent marks unless they are part of the official title. If used, ensure the system handles them without errors—some platforms may display them as question marks.

Common Metadata Mistakes to Avoid

  1. Mismatched title or author on cover vs. metadata: Even a missing comma or different spelling triggers rejection. Compare character by character.
  2. Misspelled narrator names: A typo in “Narrator” field prevents listeners from finding work by that narrator. Always copy-paste from the narrator’s official profile.
  3. Generic descriptions: “A thrilling story” tells nothing. Instead: “In 1920s Chicago, detective James Kline unravels a conspiracy linking the mayor to a string of arsons…”
  4. Keyword stuffing: Repeating the same term or using irrelevant keywords flags your submission as spam. Select 5–7 highly targeted phrases.
  5. Ignoring platform differences: Apple Books and Audible handle fields like series differently. For Apple, you may need to append the series to the title if no dedicated series field is used. ACX provides separate iTunes metadata fields—fill them appropriately.
  6. Description too short or too long: Under 200 characters may feel incomplete; over 1000 characters gets truncated on some pages. Aim for 400–700 for optimal display.

For official metadata guidelines, see ACX Metadata Requirements and Guidelines.

Advanced Tips for a Smooth Submission

Even if you meet all technical specs, a few additional practices can save you time and increase your audiobook’s performance.

Preparing Your Files

Beyond cover and metadata, your audio must meet ACX’s technical standards: -18dB RMS (plus or minus 2dB), no clipping, 44.1kHz sample rate, 192 kbps MP3 or 256 kbps AAC, with no background noise. The system reviews everything together—a rejection on audio also delays cover/metadata review. Have your audio professionally mastered if possible. Use ACX’s Audio Submission Requirements as a checklist.

Using ACX’s Validation Tools

Before final submission, use ACX’s built-in preview mode. It simulates how your audiobook will appear on Audible, Amazon, and iTunes. Check cover cropping, description truncation, and metadata displays. The validation tool catches obvious errors (like wrong image size) but won’t catch everything—like a subtle color shift. Manually double-check all fields.

Optimizing for Search and Discoverability

Write your description with the first 200 characters containing the most compelling urge and key search terms. Audible’s algorithm also considers metadata completeness and relevance. Fill every optional field (series name, narrator bio, etc.)—missing data signals lower quality. Use the 7 keywords to target long-tail phrases. For example, instead of “mystery,” use “cozy mystery small town.” Research competitor titles to see which keywords they rank for.

Handling Rejections

If your submission is rejected, read the rejection reason carefully. Common causes: cover blurry (re-export at higher quality), metadata mismatch (fix and re-check), audio levels off (remaster). Don’t just resubmit the same files; fix the root cause. ACX usually reviews within 10–15 business days. If you’re consistently rejected, consider hiring a specialist who knows ACX specs. For persistent issues, contact ACX support via your dashboard.

Final Pre-Submission Checklist

  • Cover dimensions: 2400x2400 to 3000x3000 pixels, at least 300 DPI.
  • File format: JPEG (quality high) or TIFF (uncompressed).
  • Color space: RGB (not CMYK).
  • Cover text: Only title, author, subtitle, series—no promotional text, barcodes, or URLs.
  • Title, author, narrator spelling matches cover exactly.
  • Description: 200–1000 characters, compelling, keyword-rich, no spoilers.
  • Keywords: 7 or fewer, relevant, niche-specific.
  • Language: correctly selected.
  • Optional fields filled: series name/number, narrator bio, etc.
  • Audio files: -18dB RMS, no clipping, 44.1kHz, proper format.
  • Previewed on all simulated platforms.

Conclusion

Mastering ACX’s cover art and metadata requirements is essential for any author, publisher, or narrator who wants to distribute a professional audiobook. These specifications exist to ensure a consistent, high-quality experience for listeners across devices and platforms. By following this guide—from the precise image dimensions to the strategic use of keywords—you will significantly reduce rejection risks and increase your audiobook’s discoverability. Remember, the effort you invest in these details pays off in fewer revision cycles, faster approval, and better sales performance. For further reading, explore Audible’s official best practices and Amazon Author Central for cross-platform metadata consistency. With careful preparation, your audiobook will meet the highest standards and reach the listeners it deserves.