Definition
Bleed
Bleed is printing past the trim line (usually 0.125") so ink reaches the page edge after trimming. Text-only book interiors don't need bleed; full-page images do.
Printers can't ink exactly to a cut edge, so edge-to-edge artwork is printed oversize and trimmed back. KDP asks you to declare bleed or no-bleed for interiors: novels and text-led nonfiction are no-bleed (pages exactly trim size), which is also the simpler file to verify. Offset printers that cut by crop marks expect a bleed area even around a text page — usually 3 mm (0.125 in) — with the marks set outside it, which is how Ceeryo's press-ready PDF is built.
Related tools & guides
Measure yours
Drop an interior PDF into the free KDP checker: it detects the trim, measures the inside margin on every page against the gutter your page count needs, and names the pages that fall short.