Chicago 17th vs 18th edition

In 2024, the 18th edition of the Chicago Manual of Style was released with updated guidelines to referencing. Some significant changes, clarification, updates, and additions were made to the 18th edition.

We are in the process of updating OWLL to reflect the 18th edition.

Key changes, clarifications, updates, and additions at a glance.

• Authors: Up to six authors are now listed in a bibliography (i.e. the note system) or reference list entry (i.e. the author-date system). If there are more than six authors, only the first three are listed, followed by “et al.” In a note or author-date text citation, only one or two authors are now listed. If there are more than two, only give the first author followed by “et al.” See section 13.23 and 13.107 for further detail.
• Journal month or season: A month or season does not need to be included for journals that have both a volume and an issue number. If there is no volume and/or issue, then include the month or season. Note: the season is capitalised in citations but is lower case in-text. See section 14.70 for further detail.
• Entries by the same author in the bibliography or reference list: Repeat the name of the author(s) rather than using an em dash to stand in for repeated names in bibliographies or reference lists. See sections 13.72 and 13.113 for further detail.
• Shortened citations: In notes, shortened citations are preferred over “Ibid.” Shortened citations can be used in the first reference in a note system which should have a full bibliography. “Ibid.” can only be used when it refers to the last item cited so if there is an intervening citation, then the shortened citation must be used. In a shortened citation, the page number must be repeated even if it is the same as the preceding note. See section 13.37 for further detail.
• Page range for an edited book chapter: It is no longer required to give the page range for a chapter in an edited book in the bibliography entry (although you should still give the page cited in your note). See section 14.8 for further detail.
• Publisher location: The place of publication is no longer required when citing books published since 1900. See section 14.30 for further detail.
• Omitted elements from a footnote: If a footnote element such as author or title is mentioned in-text, then it can be omitted from the footnote. See section 13.47 for further detail.
• Family name-first names: Authors who give their family name first (e.g. authors from China or Korea) are not inverted in the reference list or bibliography. See section 13.75 for further detail.
• “A”, “An” or “The” in titles: Ignore “A”, “An” or “The” when alphabetically ordering titles by the same author in a reference list or bibliography. Do not ignore non-English words like “Le” or “Un”. See section 13.100 for further detail.
• Shortened URLS: Do not use shortened versions of a URL created by a third-party such as TinyURL, Bitly or shortDOI. See section 13.11 for further detail.
• Numerals: Section 9.8 provides greater clarity about when numerals should be used and when numbers should be written as a word.
• Non-English words: Non-English words should no longer be italicised. See section 11.4 for further detail.
• Museum accession numbers: Include museum accession numbers if available when citing artworks. See Section 14.133 for further detail.

For a full list of changes see https://www.chicagomanualofstyle.org/help-tools/what-s-new.html

References and further reading

 

Disclaimer

These pages are provided as a guide to proper referencing. Your course, department, school, or institute may prescribe specific conventions, and their recommendations supersede these instructions. If you have questions not covered here, check in the style guide listed above, ask your course coordinator, or ask at Academic Q+A.

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Last updated on 10 June, 2025