Chicago Author-Date Citations

What Chicago author-date is

The Chicago Manual of Style, published by the University of Chicago Press, describes two complete systems of citation. The author-date system cites sources in the text by the author's surname and the year of publication, and lists every source in a reference list at the end of the work. The current edition, the 18th, was published in 2024.

The system is built around one idea: the author and year in the text are the first two things in the reference list entry, so a reader moves from one to the other without numbers or notes.

When to use it

Author-date is common in the physical, natural and social sciences, where the date of a finding matters and sources are cited often and briefly. Many journals and departments that otherwise follow Chicago ask for author-date; historians and many humanities fields more often use notes and bibliography.

The decision is rarely yours alone. Follow your instructor's, department's or publisher's instructions first; they may name a system, or a style based on Chicago such as Turabian.

• Not sure which style you need? Try the Citation Style Finder

Author-date and notes and bibliography

Both Chicago systems record the same information about a source; they differ in where the citation goes and in the order of the elements. The Chicago Manual of Style's own samples for the same book show the difference.

In author-date the year moves up to follow the author; in a bibliography it comes at the end, with the publisher. ResearchKit's author-date generator produces author-date only; notes and bibliography have their own guide and generator.

• Chicago Notes and Bibliography guide
• Chicago Notes and Bibliography Citation Generator

In-text citations

Cite a source in the text wherever you use its words, ideas or data. A citation gives the surname of the author, or the organization or title that stands in for one, and the year, with no punctuation between them. A page number, when you refer to a particular passage, follows a comma.

• (Yu 2020) cites the work as a whole.
• (Yu 2020, 45) points to page 45.
• (Binder and Kidder 2022, 117–18) points to a range of pages.
• No “p.” or “pp.” is used before page numbers.

Parenthetical citations

A parenthetical citation puts the author, year and page together in parentheses, usually at the end of the clause or sentence it supports, before the final punctuation.

Narrative citations

When the author's name is part of your sentence, only the year, and any page, goes in parentheses straight after it. This is not the parenthetical citation with its parentheses removed: the name stays in the sentence, and the year still sits in parentheses.

• Dittmar and Schemske (2023, 480) found that selection varied over time.
• As Yu (2020) shows, the narrative frame shapes the reader's view.
• Snyder et al. (2025) describe a detection method that needs no labels.

Reference lists

Every source cited in the text appears in the reference list, titled References, at the end of the work, in alphabetical order by the first author's surname. Each entry gives the author, the year, the title and the publication details, separated by full stops, with a hanging indent.

1. Author, first author inverted.
2. Year of publication, or n.d.
3. Title: italic for a book; in quotation marks for an article or web page.
4. Publication details: publisher; or journal, volume, issue and pages; or website.
5. DOI or URL.

One author

The author's name is inverted, family name first, followed by the given names as the source gives them. In the text, use the surname alone.

Two authors

Only the first name is inverted; the second follows in normal order after a comma and “and”. In the text, name both, joined by “and”, never an ampersand.

Three or more authors

In the reference list, list up to six authors. For more than six, list the first three followed by et al. (“and others”). In the text, from three authors on, give only the first author followed by et al.

Organization authors

When no person is named as author, Chicago allows the organization responsible for a work to serve as its author. Its name is written in full and never inverted. If real people are named as authors, cite them instead, even when an organization published the work.

When the organization's website has the same name as the organization, as in the Yale example, the name isn't repeated. When an organization is both the author and the publisher of a book, ResearchKit names it in both places and tells you so, because no Chicago rule it could confirm says to leave the publisher out.

Books

A book reference gives the author, year, italic title, edition if it isn't the first, and publisher. A place of publication is no longer required in the 18th edition. Add a DOI or URL if you consulted the book online.

The Borel sample in the Chicago Manual of Style ends with the database it was read in, EBSCOhost; the generator doesn't record databases, so its entry stops at the publisher. Tables on this page can't show italics: book and journal titles are italicized in real references.

Journal articles

An article title goes in quotation marks; the journal title is italicized. The volume follows the journal, the issue in parentheses, then a colon and the article's full page range. In the text, cite the specific page.

• When a journal numbers articles instead of paginating them, the article ID takes the place of the page range: PLOS ONE 20 (3): e0318239.
• Chicago also allows the form 202, no. 4 (April): 471–85 when the issue's month or season is cited. Choose one form and use it throughout.
• Use the year of the numbered issue, not the date the article first appeared online.

Web pages

The Chicago Manual of Style notes that web content can often simply be described in the text. When a formal citation is needed, give the author or the organization responsible, the year, the page title in quotation marks, the name of the site (not italicized), the month and day if the page gives them, and the URL.

The month and day are written as the page labels them: Google's policy is “Effective November 15”; a page might instead say “Last modified” or “Published”. The generator gives the date without a label, so add the page's own wording.

DOIs and URLs

For a source consulted online, end the reference with a URL, preferably one based on the work's DOI, written as a https://doi.org/ link. A DOI keeps working when a publisher's web addresses change.

• Give the DOI link in place of any other URL: https://doi.org/10.1086/725865.
• Copy URLs in full, including https://.
• End the reference with a full stop, even after a URL.
• Instead of a URL, Chicago also allows the name of the database where you found the source; the generator doesn't support database names.

• DOI Foundation (external link)

Page locators

Add page numbers to a text citation when you quote or refer to a particular passage. The reference list gives the full range of an article, never the page you cited.

Chicago shortens the second number of a range. Up to 100, and for multiples of 100, use all the digits (71–72, 100–104). For 101 to 109 (and 201 to 209, and so on), show only what changes (101–8, 1103–4). Otherwise use two digits, or more where they change (321–28, 1496–500).

• (Binder and Kidder 2022, 117–18)
• (Kwon 2022, 1842–43)
• For other locators, such as a chapter in an ebook without fixed pages, Chicago uses abbreviations such as chap.: (Roy 2008, chap. 6). The generator formats page numbers only.

Missing dates

When a source gives no date of publication or revision, Chicago uses n.d. (“no date”) in place of the year. For web content, add the date you accessed it, before the URL. In a parenthetical citation, a comma comes before n.d., so it isn't read as part of the name.

Look carefully before using n.d.: copyright lines, “last modified” notices and the issue a journal article appeared in all supply dates. Never guess a year.

Same author, same year

When your reference list includes two or more works by the same author from the same year, Chicago adds lowercase letters to the year, 2024a and 2024b, assigned by the alphabetical order of their titles, and uses the same letters in the text: (Smith 2024a, 12).

The letters depend on the whole reference list, which a generator formatting one source at a time can't see. ResearchKit's generator doesn't assign them; add them yourself once your list is complete.

Common mistakes

Citing consistently

• Make sure every text citation has a reference list entry, and every entry is cited.
• Check that the author and year in each citation match the entry exactly, including any 2024a and 2024b letters.
• Choose one form for journal volumes and issues and for web dates, and use it throughout.
• Give DOIs wherever works have them, and URLs only otherwise.
• Use the same name for an organization every time it appears.

When author-date may not be the right choice

Author-date works best when sources are recent, authored and dated. It is awkward for undated archival documents, manuscripts, legal and public documents, and works known by title rather than author, all of which Chicago's notes and bibliography handle more naturally. It also gives no room for commentary, which notes allow.

If your sources are mostly of these kinds, or your field expects footnotes, ask whether notes and bibliography is expected instead.

Moving between the two Chicago systems

Because both systems record the same details, converting between them is mostly a matter of moving the year and changing punctuation. Keep complete details for every source from the start, and either system can be produced later.

• Author-date reference: the year follows the author, and elements are separated by full stops.
• Bibliography entry: the year moves to the end of the publication details.
• Text citation becomes a numbered note giving the author's name in normal order, the title, the publication details in parentheses, and the page.

Using the ResearchKit Chicago Author-Date Citation Generator

1. Keep the source open while you work.
2. Choose whether it is a book, a journal article or a web page.
3. Enter each author in their own fields, as the source names them, or an organization if no person is named.
4. Enter only details you can see on the source; leave the rest blank.
5. Add a page number if you are citing a specific passage.
6. Read “Validation and notes” for anything missing or that Chicago allows in more than one form, and “How this was built” for each decision.
7. Compare the result with the source and your instructions, then copy it.

The generator runs entirely in your browser. Nothing you enter is sent anywhere or saved, and it does not look up details from a DOI or URL: it formats exactly what you give it.

• Open the Chicago Author-Date Citation Generator

Limitations of automated citation

• This generator produces author-date citations only; Chicago notes and bibliography have a separate generator.
• Headline-style capitalization and shortened titles need your judgment, so titles are used as you type them.
• Year letters such as 2024a depend on the whole reference list.
• Editors, translators, chapters, news articles, databases and other sources aren't supported yet; the generator says so rather than approximate them.
• A perfectly formatted reference can still contain a wrong date or a misspelled name. Formatting is not verification.

Learn more and check the rule

The Chicago Manual of Style is the authority for both Chicago systems; its website publishes sample citations and answers to questions from writers and editors. Your instructor's or publisher's requirements come first where they differ.

• University of Chicago Press. (2024). The Chicago manual of style (18th ed.).

• Chicago Manual of Style: author-date sample citations (external link)
• Chicago Notes and Bibliography
• MLA 9 Citation and Works Cited Guide
• APA 7 Citations and References
• How to choose a citation style

Frequently asked questions

Related guides

• Chicago Notes and Bibliography

  Learn Chicago's notes-and-bibliography system: full notes, shortened notes and bibliography entries for books, journal articles and web pages, and how it differs from author-date.

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• How to cite a website

  What to record when you use a web page, how to handle a missing author or date, when to give an access date, and how the same page is cited in APA, MLA, Chicago, IEEE and Harvard.

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• Reference list or bibliography?

  The difference between a reference list, a Works Cited list and a bibliography, which one APA, MLA, Chicago, IEEE and Harvard use, what each should contain, and how to order it.

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• How the Reference Checker Works

  What ResearchKit's Reference Checker checks in APA 7, MLA 9, Chicago, IEEE and Harvard, how it matches citations to a reference list, what it can't check, and how to read and fix what it reports.

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