A databook is an official companion book for a series, publishing reference information that the story itself does not contain: character profiles, statistics, birthdays, power system rules, timelines, and author commentary. Databooks are canon-adjacent sources of the first rank.
Databooks exist because long series outgrow their own pages. A weekly manga cannot stop to explain its power system's every rule or print a character's birthday, and readers who have followed a story for a decade want exactly those facts. The databook is the author's sanctioned overflow: organized, indexed, and sold as a companion rather than a chapter.
Their authority is what makes them valuable and occasionally contentious. A databook statement is the author or publisher speaking directly, which canon sheets treat as official word, ranked with the source itself unless the source later contradicts it. Fandom arguments are often settled by a databook page, and occasionally started by one, when a printed stat contradicts what the story showed.
This site leans on databooks openly. A subject's canon sheet lists which databooks it recognizes, and facts sourced from them are filed as such. The distinction the sheet protects is between the author's documented statements and the fandom's deductions: both circulate as facts online, and only one of them is. Collectors treat first databooks of major series as essential shelf furniture, and a subject's set of official guides is often where a fan's casual interest turns into reference-keeping.
In use"The character's birthday and the official name of that technique are not in the manga; they are in the databook."