Chicago Citation Guide: Chicago Manual of Style 18th Edition Made Clear

By MLA Generator Editorial Team · Updated May 27, 2026

Chicago is the style of historians, art historians, musicologists, and a long list of humanities and social-science fields that the Chicago Manual of Style has shaped since 1906. The current edition is the eighteenth, released in 2024, and it documents two parallel citation systems rather than one. Pick the right system for your discipline and the mechanics below tell you everything else.

The shortest version of Chicago: two systems share one manual. Author–date uses (Author Year) in the text with a “References” list at the back. Notes–bibliography uses superscript footnotes with a “Bibliography” at the back. This tool generates author–date.

What Chicago is and when you’ll use it

Chicago has been the in-house style of the University of Chicago Press since Manual of Style: Being a Compilation of the Typographical Rules in Force at the University of Chicago Press first appeared in 1906. The eighteenth edition, published in 2024, runs over a thousand pages and is the version this guide tracks. Where a rule below is keyed to a specific edition, the edition is Chicago 18.

What makes Chicago unusual among the major academic styles is that the Chicago Manual of Style (University of Chicago Press, 2024) documents two complete and parallel citation systems. Notes–bibliography uses superscript footnote or endnote numbers in the body of the text and a “Bibliography” at the end; it is the default in history, art history, religion, music, philosophy, and most humanities. Author–date uses parenthetical (Author Year) citations in the text and a “References” list at the end; it is the default in economics, political science, and most natural and social sciences that follow Chicago rather than APA. Same manual, same source data, two valid presentations. You pick one based on your discipline or your professor’s preference and you use it consistently throughout the paper. If you’re unsure which to use, our notes–bibliography comparison walks through the trade-offs in detail.

This tool generates Chicago 18 author–date citations. The engine ships the author–date variant of the official Chicago CSL style, so everything in the long in-text and reference-list sections below describes exactly what the generator produces. Notes–bibliography appears further down in its own section; if your assignment requires footnotes, you can still use the generated reference list as a starting point and adapt the in-text footnotes by hand using the rules in that section.

Author–date in-text citations

Chicago author–date is, on the surface, the same shape as APA: in-text citations with surname and year in parentheses at the end of the sentence. The differences live in the punctuation. Chicago drops the comma between author and year ((Chen 2021), not (Chen, 2021)) and writes the page number after a comma with no p. abbreviation ((Chen 2021, 47)). The author and year in the parenthetical must match the first author and year in the reference-list entry exactly.

One author

Cite the surname and the year. If the author’s name appears in the sentence, the year goes in parentheses immediately after the name and the rest of the citation does not repeat.

Parenthetical: Working memory capacity correlates with reading comprehension across age groups (Chen 2021).

Narrative: Chen (2021) found that working memory capacity correlates with reading comprehension across age groups.

Two authors

Name both authors in the parenthetical, joined by the word and (not an ampersand — Chicago is unambiguous on this). Order matches the reference-list entry.

Example: (Lin and Patel 2022)

If the names appear in the sentence, omit the parenthetical authors and keep the year: Lin and Patel (2022) argue that cross-modal attention emerges earlier than developmental psychology has typically allowed.

Three or more authors

Use the first author’s surname followed by et al. (set in roman, no italics) from the very first citation, including for three-author works. Chicago 18 collapses three-author in-text citations the same way it collapses larger groups; there is no “spell them all out the first time” phase the way some older style guides require.

First and every subsequent citation: (Goldstein et al. 2024)

The full author list appears only in the reference-list entry, up to six authors. For seven or more authors, list only the first three followed by et al. — Chicago 18 eliminated the older ellipsis convention.

Organization as author

Spell out the organization the first time and use the same form thereafter. Unlike APA, Chicago does not encourage acronym substitution in the parenthetical unless the abbreviation is genuinely standard in the discipline.

Example: (U.S. Department of Education 2023)

If you cite the same agency repeatedly and the full name becomes unwieldy, you may introduce a short form in prose (“hereafter ED”) and use it in subsequent parentheticals, but document the choice on first use.

No named author

When a work has no identified author, move the title into the author slot. Use a shortened form of the title in the parenthetical: italicized for standalone works (books, reports) and in quotation marks for shorter pieces (articles, web pages).

Web article with no author: (“Cognitive Load” 2023)

Book or report with no author: (Reading Proficiency and Learning Loss 2023)

When the source genuinely has no date, use n.d. (lowercase, with periods, no spaces). The same abbreviation appears in the reference list.

Direct quotes

Direct quotations require a locator — usually a page number, occasionally a paragraph or section number for unpaginated digital sources. The locator follows the year, separated by a comma, with no p. abbreviation.

Short quote: Working memory is “a flexible mental workspace, not a fixed bin of slots” (Chen 2021, 47).

For a website without page numbers, point the reader to whatever locator the source provides: a paragraph number (par. 4), a section heading, or a video timestamp. If nothing is available, the parenthetical is just the surname and year — do not invent a page number by counting screens.

Quotations of five or more lines (or more than one hundred words) become block quotations: indented from the left margin, no quotation marks, with the citation after the closing punctuation.

Citing multiple sources at once

When a single parenthetical points to multiple sources, separate them with semicolons. Chicago does not insist on alphabetical order the way APA does; the conventional choice is alphabetical or chronological, whichever serves the passage.

Example: Three studies converge on this pattern (Chen 2021; Lin and Patel 2022; Goldstein et al. 2024).

Two works by the same first author published in the same year are distinguished with lowercase letters appended to the year (2024a, 2024b) in both the in-text citation and the reference list.

Author–date reference list

The reference list goes on its own page at the end of the paper, with the word References centered at the top in the same font as the rest of the paper. Chicago does not bold the heading — that is APA’s convention. Every source cited in the body must appear here, and every entry here must be cited at least once in the body.

Entries are alphabetized by the first author’s surname. The page is double-spaced and each entry uses a hanging indent of half an inch, so the first line is flush left and any continuation lines are indented. Most word processors apply hanging indents through the paragraph formatting menu rather than through manual tabs.

The first author of each entry is inverted — surname first, then given name or initials. Subsequent authors appear in normal order. The year follows the author block immediately, with a period after each: Chen, Margaret S. 2021. This author-then-year placement is one of the visible cues that distinguishes a Chicago reference list from APA’s, which puts the year in parentheses: Chen, M. S. (2021).

Capitalization is title case across the board — for book titles, journal titles, article titles, chapter titles, and report titles alike. (Chicago 18 renamed the convention from “headline-style” to “title case”.) This is one of the cleaner differences between Chicago and APA: APA uses sentence case for article and chapter titles, while Chicago uses title case everywhere. The Chicago Manual of Style (University of Chicago Press, 2024) defines title case specifically: capitalize the first and last words, all nouns, pronouns, verbs, adjectives, adverbs, and subordinating conjunctions; lowercase articles, coordinating conjunctions, and prepositions of four or fewer letters unless they are the first or last word of the title. Prepositions of five or more letters are now capitalized — a change from Chicago 17, which lowercased prepositions of any length.

Chicago 18 prefers DOIs for journal articles and any other source where one exists. Format DOIs as full URLs (https://doi.org/10.1037/cogdev0000412) at the end of the entry. When no DOI is available, include the URL; Chicago retains the https:// protocol prefix on plain URLs — different from MLA, which strips it. Access dates are optional for sources with stable publication dates and recommended for sources that might change (live web pages, frequently revised reference articles, social media posts).

Source-type examples (author–date)

The references below use the fixture data referenced throughout this guide and show each common source type formatted as Chicago 18 author–date prescribes. Render them double-spaced with a half-inch hanging indent in your own document.

A few details to notice across the table. Chicago 18 made place of publication optional. Earlier editions required it, and the convention of including it (Cambridge: Cambridge University Press) is still common in humanities work, though it can now be omitted. This is a change from Chicago 17 — and another point where Chicago and APA have converged (APA 7 dropped place of publication outright). The chapter entry inverts the chapter authors but presents the editor in normal order with the edited by phrase, similar to MLA. The journal entry writes the volume and issue as 19 (2) with no italics on either; the page range follows after a colon. Page ranges use elided form per Chicago convention (142–68, not 142–168) and an en dash, not a hyphen. The dissertation puts the title in quotation marks rather than italics because Chicago treats unpublished theses as articles rather than as standalone works. If you’re entering one of these into the generator, the tool assembles the punctuation, italics, and hanging indent for you; the underlying logic is what’s shown above.

Notes–bibliography alternative

History, art history, religion, and most humanities default to notes–bibliography rather than author–date. The reference-list rules above mostly translate, but the in-text mechanics are different and the punctuation in the back matter changes.

In notes–bibliography, every citation in the body is keyed to a superscript number that points to a footnote (at the bottom of the page) or an endnote (collected at the end of the chapter or paper). The first time you cite a source, the note carries the full bibliographic information; subsequent citations of the same source use a shortened form. Whether you use footnotes or endnotes is a matter of preference — use whichever your professor or journal expects, and use the same kind throughout. The Chicago Manual of Style (University of Chicago Press, 2024) treats both as equally valid.

The two contrasting formats below show the same book — the Chen monograph from the fixture set — in both author–date and notes–bibliography. Compare them side by side and the punctuation differences become visible at a glance.

Three differences carry most of the work. First, the year moves: the author–date reference list places the year right after the author, while the notes–bibliography bibliography places the year at the end of the entry. Second, the punctuation between elements differs: the bibliography entry uses periods to separate author, title, and publication info, while the first footnote uses commas and wraps the publication info in parentheses. Third, the author’s name is inverted in both the reference list and the bibliography (Chen, Margaret S.) but stays in normal order in the footnote (Margaret S. Chen). The subsequent shortened note uses just the surname, a short title, and the page number — and the Chicago Manual (2024) discourages the old Ibid. shortcut in favor of this short-form approach.

Common mistakes

These five errors account for most of the marks students lose on Chicago assignments. Each shows the wrong version above the right one.

Comma between the author and the year. Wrong: (Chen, 2021) Right: (Chen 2021)

The comma is APA’s convention. Chicago author–date drops it. If you’ve taken classes in both styles, the muscle memory will fight you.

Ampersand between authors in the parenthetical. Wrong: (Lin & Patel 2022) Right: (Lin and Patel 2022)

Chicago spells out and in both the in-text citation and the reference list — no ampersand in either. APA uses an ampersand in parentheticals, which is the source of the confusion.

Sentence case in a title. Wrong: Chen, Margaret S. 2021. The architecture of working memory. Right: Chen, Margaret S. 2021. The Architecture of Working Memory.

Chicago uses title case for every title — book, journal, article, chapter. Sentence case is APA’s habit, not Chicago’s, and using it makes a Chicago reference list look amateur at a glance.

Stripping the protocol prefix from URLs. Wrong: www.psychologytoday.com/intl/blog/working-memory-reading-comprehension Right: https://www.psychologytoday.com/intl/blog/working-memory-reading-comprehension

This one trips writers coming from MLA. MLA 9 strips http:// and https:// from plain URLs; Chicago retains the protocol prefix. DOIs keep the https://doi.org/ prefix in both styles because the prefix is part of the canonical identifier.

Using Ibid. for repeated footnote citations. Wrong: 7. Ibid., 92. Right: 7. Chen, Architecture of Working Memory, 92.

The Chicago Manual of Style (University of Chicago Press, 2024) discourages Ibid. in favor of the shortened-citation form. The shortened form is easier for readers because it stays informative even when the previous note has scrolled off the page or has been moved during revision.

What’s new in Chicago 18

The eighteenth edition is the first major revision of the manual since 2017, and the changes mostly run in the direction of expanded coverage for digital sources and inclusive language. If you’ve worked with Chicago 17, these are the differences that matter.

Explicit guidance on AI-generated content. Chicago 18 added formal rules for citing AI-generated text, images, and other outputs. Treat the AI service as the author, include the prompt or a short description of what you asked for, and record the date you used the tool. The seventeenth edition predated the explosion of generative AI in academic workflows; the eighteenth catches the manual up.

Expanded digital-source treatment. Chicago 18 added or revised worked examples for preprints (arXiv, SSRN, bioRxiv), social-media posts across platforms, podcast episodes, streaming video, and dataset citations. Earlier editions handled some of these in scattered notes; the eighteenth treats them as first-class source types.

Author–date as a more visible default. Chicago 17 already documented both systems, but the eighteenth edition surfaces author–date earlier and more prominently and notes its growing adoption outside the social sciences. The manual no longer treats notes–bibliography as the “real” Chicago and author–date as an alternative; both are equal first-class citizens.

Inclusive-language updates. Chicago 18 expanded its guidance on singular they, on identity-first versus person-first language for disability and neurodivergence, on bias-free language for race and ethnicity, and on the treatment of pronouns in author bylines. These changes parallel similar updates in APA 7 and MLA 9 but go further in places.

Shortened-citation preference over Ibid. Chicago 17 already preferred shortened citations to Ibid.; the eighteenth makes the preference firmer. Ibid. is still permitted but is no longer recommended.

Et al. threshold lowered for in-text citations. Chicago 17 spelled out two- and three-author works in full in the in-text citation and reserved et al. for four or more authors. Chicago 18 lowers the threshold: three or more authors now collapse to First et al. from the very first citation. The reference-list cutoff also moved — Chicago 17 listed up to ten authors before switching to an ellipsis convention; Chicago 18 lists up to six authors and uses First three et al. for seven or more, eliminating the ellipsis entirely.

Place of publication is now optional. Chicago 17 required the publisher’s city in book and report entries. Chicago 18 makes it optional (§14.30). Including the city is still common in humanities work, but you may now omit it — bringing Chicago closer to APA, which dropped place of publication outright in APA 7.

Title case capitalizes longer prepositions. Chicago 17 lowercased prepositions of any length in titles. Chicago 18 capitalizes prepositions of five or more letters and lowercases only those of four or fewer. The manual also renamed the convention from “headline-style” to “title case.”

The mechanics most readers care about — author–date parentheticals, alphabetized reference lists with hanging indents, title case across the board, the bibliography-versus-footnote distinction in notes–bibliography — are broadly continuous with Chicago 17. The eighteenth edition refines and expands; it does not rebuild.

Editorial methodology and sources