Library Guides: Chicago Style (18th Edition) Citation Guide: What's New in the 18th Edition

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.” (See 13.23 and 13.78)
If the same person is cited as both author and editor of a work, the name is given in full for both roles (See 14.12)
An illustrator of a children's book can be cited similarly to an editor or translator (See 14.6)
Chicago now prefers repeating the name of the author(s) rather than using a 3-em dash to stand in for repeated names in bibliographies or reference lists (See 13.72)

An initial “A,” “An,” or “The” in a title is ignored when alphabetizing successive works by the same author by title in a bibliography or reference list (but a “Le,” “Un,” or the like is not ignored) (See 13.100)
The subtitle “A Novel” can usually be omitted when the title of a book is mentioned or cited, even if it appears on the title page (See 13.91)

Digital Object Identifiers (DOIs) should be formatted as a URL, such as: https://doi.org/10.1086/718629. Formatting DOIs as doi:... is considered a deprecated usage (See 13.7)

Caution against using older secondary sources of indigenous knowledge; acknowledging oral sources is preferable (See 14.136–37)

A month or season can now usually be omitted in citations of journal articles (See 13.26 and exceptions 14.70)
For articles published online in advance of a print issue, include "ahead of print" as well as the posted publication date, volume, and issue (if available) (See 14.75)
For articles that have been accepted for publication but not copyedited yet, use "forthcoming" and indicate the date the article was accepted (See 14.75)
Preprints are cited similar to journal articles; include "preprint" followed by the name of the preprint server in place of the journal volume or issue number (See 14.76)

A place of publication is no longer required in citations of books published since 1900 (See 14.30)

The page range for a cited chapter in an edited book is no longer required in a bibliography or reference list entry (though a page range is still required for most journal articles) (See 14.8)
When citing entries in reference works, in the footnote, use "under" rather than "s.v." or "s.vv." (See 14.130)

Information about a cited presentation is no longer enclosed in parentheses in a note (See 14.115)