Six checks catch most KDP coloring-book interior problems before upload: 300 DPI at the trim size used, 1-bit line art (no gray edge pixels), page count inside the printable range for the trim and paper chosen, the gutter matching that interior page count, safe margins respected on every page, and every page present — no missing, placeholder, or failed pages in the finished file.
The six checks
| # | Check | What it catches |
|---|---|---|
| 1 | 300 DPI at the trim's pixel size | Files too small for the print size |
| 2 | 1-bit line art, no gray pixels | Anti-aliasing and JPEG halos that print soft |
| 3 | Page count in the printable range | A too-short file that won't bind, or one over the trim's max |
| 4 | Gutter matches interior page count | Content pulled toward the spine after binding |
| 5 | Safe margins on every page | Content lost to trimming variance at outer edges |
| 6 | Every page present, none missing or failed | A dropped, placeholder, or blank-by-accident page that changes the count and the gutter band |
Why these six and not more
Each check corresponds to a distinct way a coloring-book interior can fail — they don't overlap. Resolution and color depth (checks 1 and 2) are both about whether a line reproduces cleanly, but they're independent settings that can each fail without the other (see the 1-bit vs. grayscale guide). Page count, gutter, and margins (checks 3–5) are all specific ranges, but each is keyed to something different — trim and paper for the count, interior page count for the gutter, a fixed inch minimum for the margins — so passing one says nothing about the others. Completeness (check 6) is what ties the others to reality: a page that never finished or was dropped changes the real page count, which can move the gutter band, so checks 3 and 4 are only trustworthy once check 6 passes.
Running the checks in order
Resolution and color depth should be confirmed per page before anything else, because a page that fails either one needs to be regenerated, which can change its dimensions and reset the other checks for that page. Page count, gutter, and margins are file-level: page count decides the gutter band, and both are worth locking before doing a margin pass on every page, since a page-count change after margins are set means redoing that pass. Completeness is the last check — confirming every page is present only makes sense once the file's final page count and layout are settled, and it is the one to repeat after any late regeneration.
What a checklist won't catch
A checklist run page by page can still miss how two facing pages look together once the book is bound and opened — content that's individually inside the safe margin on both pages can still look uneven across the spine. KDP's online previewer renders spreads the way a printed and bound copy will show them, which is the reason to open it before publishing even after every item on this list passes. A checklist reduces how much the previewer needs to catch; it isn't a replacement for it.
Automating it
Running six checks by hand across dozens of pages is where mistakes creep in — a page regenerated late in the process, checked individually, but not re-checked against the file's final gutter setting. CrayonMill's export check runs the same six — every page ready with none failed, 1-bit, interior page count inside CrayonMill's supported 24–300 window (KDP itself allows more), gutter for that count, outer safe margin, and resolution — from the book's current state before the download button unlocks, and re-evaluates the moment any page's status changes.
Sources
Last verified 2026-09-04. Updated 2026-09-04.