Knowledge
Rules
Citeable definitions for submission rules Cermify tracks. Public fields only — not detection or repair logic.
- Invalid HTML/CSS construct (RSC-005 family) — Your EPUB contains HTML or CSS that KDP's validator flags as invalid (commonly reported as RSC-005). This usually comes from exporters like …
- Missing or mismatched NCX / nav document — Kindle needs a table-of-contents navigation file (NCX for EPUB 2, nav doc for EPUB 3). Yours is missing or doesn't match your chapter headin…
- Table of contents points to missing content — One or more TOC entries link to an id or file that no longer exists in your book, which breaks Kindle's chapter navigation.…
- Missing required metadata (title, language, identifier) — Your package file (OPF) is missing required metadata KDP expects: title, language, or a unique identifier.…
- Reading order (spine) is empty or broken — Your book's reading order (the 'spine') is missing entries or points to files that don't exist, so Kindle doesn't know what order to show pa…
- Incorrect or missing mimetype / manifest entries — Your EPUB's mimetype file or manifest doesn't correctly declare all the files inside the package, which is a hard requirement for EPUB valid…
- Non-UTF-8 encoded content file — One of your chapter files isn't encoded as UTF-8, which can cause garbled text or validator failures on Kindle.…
- Severe HTML nesting errors — Some HTML tags in your book are nested incorrectly (e.g. a paragraph inside another paragraph), which can break rendering.…
- Broken or malformed ebook link — A link inside your book points to a missing EPUB file or anchor, or an external URL is missing its protocol.…
- Risky CSS for Kindle layout — Your stylesheet references an external CSS resource or forces global text justification, which can create Kindle upload or layout problems.…
- Referenced image file is missing — Your book references an image file that isn't included in the EPUB package. We report this but do not generate replacement art.…
- Font file not declared in manifest — A font file exists in your EPUB but isn't listed in the manifest, so it may not load correctly.…
- Full wrap size does not match trim + spine + bleed — The uploaded cover canvas or PDF page box does not match the expected KDP full-wrap size for your trim, spine width, and bleed settings.…
- Spine width differs from page count / paper calculation — The spine band width on your cover does not match the width calculated from final page count and paper type, so spine text and folds can mis…
- Missing bleed or artwork does not reach bleed edge — Bleed is required for your paperback settings, but the artwork or background does not extend to the full bleed boundary.…
- Text or critical art outside the safe zone — Critical cover content sits too close to trim or fold edges and may be clipped or hard to read after binding.…
- Content collides with KDP barcode clear zone — Text, logos, or artwork overlap the paperback barcode clear zone on the back cover, which can block KDP's barcode or make it unreadable.…
- Raster cover below print-quality DPI — The cover raster resolution is below ~300 DPI at print size, or DPI metadata is missing, so print output may look soft or pixelated.…
- Front-only cover uploaded where full wrap is required — The upload appears to be a front-only cover, but KDP paperback export needs a full wrap that includes back cover, spine, and front cover.…