kdp-cover-checker

name

kdp-cover-checker

description

Validate KDP book cover PDFs against Amazon's dimension, bleed, and DPI specifications, AND check that no cover TEXT sits in the trim-unsafe margin (the #1 reject reason). Checks cover width/height based on page count and spine calculation, verifies 0.125" bleed on all sides, ensures minimum 300 DPI, and renders a safe-zone overlay. Supports both 8.5x11 (portrait) and 8.5x8.5 (square) trim sizes. Can check a single book or scan all books in output/ folder. USE WHEN user says 'check cover', 'verify cover', 'validate cover', 'kiem tra bia', 'cover dimensions', 'cover size check', 'kdp cover check', 'cover compliance', 'check all covers', 'are my covers correct', 'cover specs', 'kiem tra kich thuoc bia', 'text too close to edge', 'cover bi tu choi', 'safe zone', 'chu sat mep'.

KDP Cover Checker

Validate KDP book cover PDFs against Amazon's exact dimension and quality specifications.

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When to Run

• After generating covers with /kdp-cover-creator or generate_cover.py
• Before uploading to KDP to catch dimension errors
• When KDP rejects a cover for wrong dimensions
• To audit all books in the output/ folder at once

How to Run

Execute the checker script:

# Check ALL books in output/
python .claude/skills/kdp-cover-checker/scripts/check_covers.py

# Check a single book
python .claude/skills/kdp-cover-checker/scripts/check_covers.py --theme cozy_cats_daily_life

# Verbose mode (show all details even for passing books)
python .claude/skills/kdp-cover-checker/scripts/check_covers.py --verbose

KDP Cover Specifications

These are the exact rules the checker validates:

Bleed (mandatory for covers)

• All covers MUST include 0.125" bleed on all 4 sides
• This is non-negotiable — KDP rejects covers without bleed

Spine Width Formula

spine_width = total_pages * 0.002252"

Where total_pages = the interior PDF page count (white paper, black ink).

Full Cover Dimensions

width  = 8.5" (back) + spine + 8.5" (front) + 0.125" (bleed left) + 0.125" (bleed right)
height = trim_height + 0.125" (bleed top) + 0.125" (bleed bottom)

Example for 8.5x8.5 square, 104 pages

• Spine: 104 * 0.002252 = 0.234"
• Width: 8.5 + 0.234 + 8.5 + 0.125 + 0.125 = 17.484"
• Height: 8.5 + 0.125 + 0.125 = 8.750"
• At 300 DPI: 5245 x 2625 px

Example for 8.5x11 portrait, 56 pages

• Spine: 56 * 0.002252 = 0.126"
• Width: 8.5 + 0.126 + 8.5 + 0.125 + 0.125 = 17.376"
• Height: 11 + 0.125 + 0.125 = 11.250"
• At 300 DPI: 5213 x 3375 px

DPI

• Minimum 300 DPI required

Text safe zone (the #1 reject — ALWAYS check this)

KDP trims the wrap ~0.125" in (bleed) and the printer can drift another ~0.25", so any TEXT within 0.375" of the trim line (= 0.5" / 150px from the file edge at 300 DPI) can be shaved off. The rejection email reads "move all text at least 0.375 inches (9.5 mm) away from all edges." This is the most common reason a cover comes back.

Run the safe-zone checker — it writes output/{theme}/cover_safe_check.png (green = trim, red = text-safe line) and prints per-edge ink %:

python scripts/check_cover_safezone.py <theme_key>
# or on an explicit file:  python scripts/check_cover_safezone.py --png output/<theme>/cover.png

The overlay is the real gate, not the number. OPEN cover_safe_check.png and confirm no letter, number, or text badge crosses the RED line. Decorative art (balloons, confetti, sparkles, gift boxes, bunting) crossing the red line is FINE — only text must stay inside. On full-bleed vibrant covers the ink % runs high on every edge (decoration bleeds); trust the picture. If any text crosses: for AI-baked front text, re-roll the front with the title/badges/ author pulled into the central ~75% (see the kdp-chatgpt-cover-creator prompt rules); for code overlays, move them inward (--headline-y, --badge-x, etc.).

Tolerance

• Dimension tolerance: +/- 0.01" (3 pixels at 300 DPI)
• This accounts for rounding in pixel-to-inch conversion

Understanding the Output

The checker reports for each book:

[PASS] cozy_cats_daily_life
  Pages: 104 | Size: 8.5x8.5 | Spine: 0.234"
  Expected: 17.484" x 8.750" | Actual: 17.484" x 8.750"

[FAIL] farm_animals_bold — WIDTH MISMATCH
  Pages: 56 | Size: 8.5x11 | Spine: 0.126"
  Expected: 17.376" x 11.250" | Actual: 17.250" x 11.250"
  Delta: width off by -0.126" (missing spine width?)

[SKIP] dragons_cute_friendly — no cover.pdf found

What to Do with Failures

• Width too small: Usually means spine width wasn't included or page count changed after cover was generated. Regenerate the cover.
• Height wrong: Check if the correct page size (8.5x11 vs 8.5x8.5) was used.
• DPI too low: The cover image was saved at less than 300 DPI. Regenerate with --dpi 300 or check the source image resolution.
• Missing cover.pdf: Run /kdp-cover-creator for that theme.

Page Count Detection

The script determines page count by:

1. Counting PNG images in output/{theme}/images/ directory
2. Calculating total pages: 2 (title + copyright) + (num_images * 2) + 1 (thank you), rounded up to even

This matches the logic in generate_cover.py and build_pdf.py.