Chicago A: 18th edition

The Chicago Manual of Style has two systems: author-date and notes and bibliography. This guide refers to the notes and bibliography system, based on the 18th edition. This is Chicago's oldest and most flexible system of source citation. For information about the author-date system, see the Chicago manual of style - Author-Date: Sample Citations.

This guide is designed to help you:

• apply the Chicago 18th A: Notes and Bibliography format to different types of resources
• check your work against examples.

If you require guidance on the previous edition, see our Chicago A (Notes & bibliography) 17th edition .

Additional resources

Some of the more important changes include:

• AI-generated content:  New guidance provided. (14.112)
• First Peoples' Knowledges: New guidance provided. (14.136-37)
• Ebooks: Books consulted in fixed-page format, where the online version matches a printed counterpart can be cited without naming the format (as if it were in print). Reflowable formats (for example, Kindle, Apple Books) should be noted. (14.58)
• Multiple authors:  Up to six authors are now listed in a bibliography or reference list entry; if more than six, only the first three are listed, followed by “et al.” In a shortened note or an author-date text citation, up to two authors are now listed; if more than two, only the first is listed, followed by “et al.” (13.23)
• First author names in bibliography: When listing authors whose cultural naming conventions place the family name first (as in many Asian, Hungarian, and other naming traditions), maintain this original order without inversion in the bibliography or reference list. (13.75)
• Title case: Title case (previously called headline style) is the capitalisation style used in the 18th edition. Prepositions of five or more letters are now capitalised in headlines.  For example, Words into Type, but Much Ado About Nothing. (8.160)
• Place of publication: This is no longer required in the citations of books and book chapters. (14.30)
• Page numbers of chapters: The page range for a cited chapter in an edited book is no longer required in a reference list entry (though a page range is still required for most journal articles). (14.8)
• URLs: Do not create shortened versions of URLs via third-party services such as TinyURL, Bitly or short DOI. (13.11)

For a full list of changes and clarifications, see the information listed under Chapters 13 and 14 of What's New in the 18th edition.