Qidian's book number was a digital copyright identification code used to prove that a book had been published on Qidian. Qidian's role was to protect the author's intellectual property rights from unauthorized plagiarism and pirated versions. To create a new book on Qidian platform, one needed to obtain a book number before they could publish the new book on the platform. After the book was published, it would be marked as "published" to prevent other authors from copying the content of the book. The book number could also be used to calculate the author's income. On the Qidian platform, the author's chapter income would be calculated according to the number of words and clicks. Each chapter needed a book number to be included in the system. Therefore, having a book number could protect the author's income. Qidian's book number was one of the important measures taken by Qidian to protect intellectual property rights. It was an important guarantee for both authors and readers.