Chicago Style 18th Edition: A Complete Guide

Updated May 2026.

Chicago Style, set out in The Chicago Manual of Style, is the citation and editorial framework used in history, art history, theology, religious studies, music, philosophy of religion, and most of trade book publishing. It is the most comprehensive of the three major American style guides, covering not just citation but also editing practice, manuscript preparation, copyright, publishing workflow, and writing mechanics across more than a thousand pages.

The current edition is the 18th, published by the University of Chicago Press in September 2024. It is the first major revision in seven years and the most extensive update in two decades. If you are writing for a Chicago-style discipline or publisher today, the 18th edition is the version you should be applying, unless your instructor or publisher has told you to use the older 17th edition for a specific reason.

This guide is the central reference point for Chicago Style at Editor World. It explains what Chicago covers, why the manual offers two complete citation systems (notes-bibliography and author-date) instead of one, what changed between the 17th and 18th editions, and which of Editor World's deeper Chicago articles to read for each specific question that comes up.

What Chicago Style Is

Chicago Style is the editorial framework set out in The Chicago Manual of Style, published by the University of Chicago Press. It has been in continuous publication since 1906, longer than any other major American style guide, and is currently in its 18th edition. The Chicago Manual of Style Online is the subscription-based digital edition that mirrors the print manual; the free Chicago Citation Quick Guide covers the most common source types in both systems and is accessible without a subscription.

Chicago is the default citation style across most disciplines where the documentary trail itself is part of the scholarship. The fields that use Chicago as the standard include history, art history, religious studies, theology, classical studies, musicology, philosophy of religion, and parts of literature and film studies. It is also the editorial framework most US trade book publishers use, the basis for the style guides of the American Anthropological Association and the Organization of American Historians, and the foundation for Kate Turabian's A Manual for Writers of Research Papers, Theses, and Dissertations, the simplified version of Chicago used in many graduate schools.

For an overview of how Chicago compares to APA and MLA, see Editor World's overview of citation styles, which explains when each style is required and how the discipline determines the choice.

Why Chicago Offers Two Systems

Chicago is unusual among major citation styles because it provides two complete, fully developed citation systems and asks the writer to choose between them based on discipline. APA has one system. MLA has one system. Chicago has two, and the choice is not optional. A writer using Chicago must pick one and apply it consistently throughout the document. The two systems serve different scholarly cultures.

Notes-bibliography

The notes-bibliography system uses superscript numbers in the body of the paper, full bibliographic information in numbered footnotes (or endnotes) at the bottom of each page, and a complete bibliography at the end of the document. This is the system used in history, art history, religious studies, theology, and most of trade nonfiction. It looks like the citation system in a serious nonfiction book because that is what it was designed for.

The reason historians and humanists use notes-bibliography rather than author-date is that the documentary trail in their disciplines is itself part of the argument. A historian writing about the French Revolution often needs to comment on the source, qualify the source, compare it to another source, or discuss how the source has been interpreted in earlier scholarship. A parenthetical in-text citation cannot carry that kind of commentary. A footnote can. Chicago's notes-bibliography system gives historians the space to think on the page about the evidence as well as to point to it.

Author-date

The author-date system uses parenthetical citations in the text, with the author's last name and the publication year, similar to APA. The full reference appears in a reference list at the end of the document, organized alphabetically. This is the system used in the natural sciences, the social sciences, economics, and some areas of political science when those fields use Chicago rather than APA.

The choice between the two systems is determined by discipline, not by writer preference. If you are submitting to a history journal, you use notes-bibliography. If you are submitting to a Chicago-style economics journal, you use author-date. Mixing the two systems in a single document, or choosing the wrong one for your discipline, is a fast way to have a manuscript returned for revision.

What Changed in the 18th Edition

The 18th edition of The Chicago Manual of Style was published in September 2024, replacing the 17th edition (2017). The publisher called the 18th edition the most extensive revision in two decades, and the description is accurate. Several changes affect day-to-day citation practice; several others affect editorial practice more broadly. The major changes are listed below.

• Publisher location dropped from book citations. Chicago 17th required the city of publication (and country, for foreign publishers) in book citations: The Science of Maps (New York: Yale University Press, 2021). Chicago 18th drops the city: The Science of Maps (Yale University Press, 2021). For books published since 1900, the city is no longer required in either the notes or the bibliography.
• Guidance added for AI-generated content. Chicago 18th introduced formal guidance for citing AI-generated text and images. Writers who use AI tools in research must disclose and cite that use, with specific formats for ChatGPT, image generators, and other generative tools. The guidance recognizes that AI output is not a stable, reproducible source the way a published work is.
• Ibid. replaced by shortened notes. Chicago 17th used the abbreviation ibid. ("in the same place") to refer to the immediately preceding source in a footnote. Chicago 18th recommends a shortened note instead, repeating a brief form of the author and title. The change makes the footnotes easier to read for the modern reader and parallels the move away from Latin abbreviations elsewhere in academic style.
• Expanded inclusive language coverage. Chicago 18th expanded the chapter on inclusive language with detailed guidance on writing about race, ethnicity, gender, sexual orientation, disability, age, and Indigenous peoples. The treatment parallels updates in APA 7th and MLA 9th.
• Page ranges no longer required for chapters in bibliographies. Chicago 17th required a page range when citing a chapter in an edited book in the bibliography. Chicago 18th makes the page range optional in the bibliography entry, though it remains required in the footnote and in most journal article citations.
• Expanded coverage of fiction and self-publishing. The manual has historically been oriented toward nonfiction, scholarship, and traditional publishing. Chicago 18th significantly expanded the treatment of fiction (punctuation in dialogue, scene breaks, fictional naming conventions) and self-publishing workflows (cover copy, metadata, ISBN registration, distribution).
• New guidance on accessibility. Chicago 18th added detailed guidance on making publications accessible to readers with disabilities, including alt text for images, captioning conventions, and formatting practices for screen readers.
• Expanded coverage of Korean, Indigenous languages, and non-English sources. Chicago 18th expanded the treatment of citations in non-English languages, with new sections specifically on Korean transliteration and on the citation of Indigenous-language sources.
• Mathematics chapter removed. Chicago 17th included a chapter on mathematics in type. Chicago 18th removed it, citing low usage. Writers preparing manuscripts with significant mathematical content should reference a discipline-specific style guide.

If your Chicago reference materials, templates, or citation manager were last updated before September 2024, they are still applying 17th-edition rules. The publisher-location change is the most visible difference and is the easiest one to miss when updating older citations.

How the Notes-Bibliography System Works

The notes-bibliography system is the more visible of the two, and the one most readers think of when they think of "Chicago Style." It has three components.

The superscript number

In the body of the paper, a superscript number is placed at the end of the sentence containing the cited material, after the closing punctuation. The number corresponds to a footnote at the bottom of the page (or to an endnote in the endnotes section, depending on the publisher's preference). Footnotes are numbered consecutively through the document, not restarted on each page or in each chapter.

The footnote

The first time a source is cited, the footnote contains the full bibliographic information, formatted as a sentence-style reference with commas separating the elements: author first name and last name, title, publication information in parentheses, and page number. For example:

1. Margaret Hollis, Maps of Power: Cartography and Empire (Yale University Press, 2021), 47.

Subsequent citations to the same source use a shortened note containing only the author's last name, a shortened version of the title, and the page number:

12. Hollis, Maps of Power, 84.

In Chicago 18th, the shortened note replaces the older "ibid." abbreviation that 17th-edition writers used to refer to the immediately preceding source.

The bibliography

At the end of the document, a bibliography lists every source consulted in the preparation of the paper, including sources read for background research that were not directly cited. Entries are organized alphabetically by the first author's last name. Each entry uses a hanging indent: the first line is flush left, and subsequent lines are indented half an inch. The bibliography is single-spaced within each entry with a blank line between entries, or double-spaced throughout depending on the publisher's house style.

Bibliography entries differ from footnote entries in two important ways. First, the author's name is inverted (last name, first name) for alphabetization. Second, the entry uses periods to separate the main elements rather than the commas used in footnotes:

Hollis, Margaret. Maps of Power: Cartography and Empire. Yale University Press, 2021.

For the full mechanics of Chicago bibliography formatting, including source-type breakdowns and the most common bibliography mistakes, see Editor World's guide on how to write a Chicago style bibliography.

How the Author-Date System Works

The author-date system is simpler and visually closer to APA. It has two components.

The in-text citation

In the body of the paper, sources are cited in parentheses with the author's last name and the publication year, no comma between them: (Hollis 2021). When citing a specific page, the page number follows the year, separated by a comma: (Hollis 2021, 47). For two authors, both names are joined by "and": (Hollis and Patel 2022). For three or more authors, the first author's name is followed by "et al.": (Hollis et al. 2023, 47).

The reference list

At the end of the document, a reference list (titled References) provides full bibliographic information for every source cited. Unlike a notes-bibliography bibliography, the reference list contains only the sources actually cited, not sources consulted for background research. Entries are organized alphabetically by the first author's last name, with the publication year placed immediately after the author's name to align with the in-text citation:

Hollis, Margaret. 2021. Maps of Power: Cartography and Empire. Yale University Press.

The early placement of the year is the most visible difference between Chicago author-date and notes-bibliography reference formats. Everything else is similar in spirit but differs in specific punctuation and structure.

Choosing the Right System

The choice between notes-bibliography and author-date is made by discipline, not by personal preference. Use this sequence to identify which system applies.

Step 1: Check the assignment, journal, or publisher instructions

Many instructors, journals, and publishers specify the system directly. If your syllabus says "Chicago notes-bibliography" or your journal's author guidelines say "Chicago author-date," use what they say. Submission instructions override discipline conventions.

Step 2: Identify your discipline default

In the absence of explicit instructions, the discipline determines the system. Notes-bibliography is the standard in history, art history, religious studies, theology, classical studies, musicology, philosophy of religion, parts of literature and film studies, and trade nonfiction publishing. Author-date is the standard in economics, anthropology, archaeology, parts of political science, and the natural sciences when those fields use Chicago rather than APA.

Step 3: Look at recent papers in your target venue

If you are still unsure, look at recent papers in the journal you are submitting to or the dissertations recently approved in your department. The system they use is the system you should use. Mixing notes-bibliography conventions with author-date conventions in a single document is one of the most-flagged errors in Chicago-style writing.

Most Common Chicago Mistakes and How to Fix Them

The same five issues appear in nearly every paper that comes back marked up for Chicago errors. Each one is correctable in a single editing pass once you know to look for it.

Mistake 1: Including the publisher's city in a citation

Before (footnote): 1. Margaret Hollis, Maps of Power: Cartography and Empire (New Haven: Yale University Press, 2021), 47.

After (Chicago 18th): 1. Margaret Hollis, Maps of Power: Cartography and Empire (Yale University Press, 2021), 47.

Chicago 18th dropped the publisher's city from book citations for works published since 1900. The city is no longer required in either the footnote or the bibliography. Citation managers and reference templates that were last updated before September 2024 are still inserting the city automatically, and that is now an error.

Mistake 2: Using ibid. instead of a shortened note

Before: 5. Ibid., 84.

After (Chicago 18th): 5. Hollis, Maps of Power, 84.

Chicago 17th used ibid. ("in the same place") to refer to the immediately preceding source. Chicago 18th recommends a shortened note instead. The change makes the footnotes easier to read and removes a Latin abbreviation that contemporary readers often have to look up.

Mistake 3: Mixing the two systems in one document

A paper using notes-bibliography uses superscript numbers in the text and full bibliographic information in footnotes. A paper using author-date uses parenthetical in-text citations and a reference list at the end. Mixing the two (footnotes in some places, parentheticals in others; a bibliography for some sources and a reference list for others) is a fast tell that the writer has not chosen a system and stuck with it. Pick one based on your discipline and apply it consistently.

Mistake 4: Confusing a bibliography with a reference list

A bibliography (used in notes-bibliography) includes every source consulted in the preparation of the paper, including sources read for background research that were not directly cited. A reference list (used in author-date) includes only the sources actually cited. The two are not interchangeable. Writers sometimes apply APA's "References" convention to Chicago notes-bibliography papers and end up with a list that omits the background sources the bibliography is supposed to include.

Mistake 5: Wrong punctuation between footnote and bibliography formats

Before (bibliography entry): Hollis, Margaret, Maps of Power: Cartography and Empire, Yale University Press, 2021.

After (bibliography entry): Hollis, Margaret. Maps of Power: Cartography and Empire. Yale University Press, 2021.

Chicago bibliography entries use periods to separate the main elements. Chicago footnote entries use commas. Mixing the two punctuation conventions is the single most-common Chicago error. The pattern to remember is this: footnotes read like sentences (commas, parenthetical publication info), bibliography entries read like a list of facts (periods, no parentheses).

When Chicago Is Not the Right Style

If your discipline is history, art history, religious studies, theology, musicology, philosophy of religion, or trade book publishing, Chicago is almost certainly the right style. If your discipline is something else, double-check before assuming Chicago applies.

Psychology, education, nursing, business, and the social sciences use APA. English, literature, languages, and most of the humanities outside history use MLA. Medical journals use AMA. Engineering and computer science use IEEE. Biology and the natural sciences use CSE. Within any of these fields, individual journals may have their own house style that overrides the discipline default.

Graduate students writing dissertations should also check whether their institution requires Turabian rather than full Chicago. Turabian is a simplified version of Chicago developed specifically for student papers, theses, and dissertations, and many graduate schools require Turabian formatting rather than Chicago for dissertation submission. The two are closely related but not identical; the institutional requirement is the authority.

The Editors Who Handle Chicago Editing at Editor World

Editor World's editors include credentialed humanities professionals with strong backgrounds in Chicago Style work across history, theology, philosophy, art history, and trade book publishing. Clients browse editor profiles, review credentials and verified client ratings, and choose the editor whose background matches the document. Below are several editors with credentials directly relevant to Chicago-style editing.

• BookDoc. MFA in Writing (New York University), Senior Copy Editor at NYU, certified editor with the International Association of Professional Writers and Editors. 4.92/5 client rating. Book editing is the home territory of Chicago Style, and BookDoc's NYU senior copy editor background is one of the strongest matches on the Editor World roster for Chicago-style manuscript work. View profile.
• TypeRighter. BA and MA in Philosophy, Certified Teacher with the Cambridge Institute of Education. 4.98/5 client rating across 1,300+ ratings. Strong background in humanities citation work, including Chicago notes-bibliography for philosophy and religious studies. View profile.
• WriteAid. BA in English Literature (Binghamton University), MS in Psychology, PhD candidate at Walden University. Over 20 years of editing, teaching, and writing experience. 4.92/5 client rating. Cross-disciplinary background applicable to Chicago author-date work in the social sciences as well as notes-bibliography work in the humanities. View profile.

A full list of currently available editors is at editorworld.com/editors. Clients select their editor before submitting a document and can request a free sample edit to verify fit before committing.

Why Choose Editor World for Chicago Editing

• Recommended by the Boston University Economics Department. Editor World is among the editing services recommended to Boston University students for academic editing support.
• Choose your editor. Browse profiles, credentials, and verified client ratings before submitting. You aren't assigned an editor at random.
• 100% human editing, no AI at any stage. Chicago compliance depends on judgment about edition-specific exceptions, system-specific conventions (notes-bibliography versus author-date), and publisher house overrides that AI tools handle poorly. Editor World's editors do not use AI tools to edit documents.
• Chicago 18th expertise. Editors apply Chicago 18th edition rules correctly, including the publisher-location change, the shortened-note replacement for ibid., the expanded inclusive language guidance, and the new AI-citation conventions that older templates do not include.
• Both systems supported. Editors work in Chicago notes-bibliography for history, humanities, and trade publishing, and in Chicago author-date for economics, anthropology, and the social sciences. Turabian is also supported for graduate-school dissertation work.
• Native English speakers from the USA, UK, and Canada only. Editors apply the conventions of the variety required by your document.
• Certificate of editing. Available as an optional add-on. Useful for journal submissions, dissertation submissions, and book manuscripts that require external editing verification.
• Fast turnaround. Same-day editing is available with 2-hour, 4-hour, and 8-hour options. Longer documents are scheduled for one-day, two-day, or three-day turnaround.

Get Your Chicago Manuscript Reviewed Before Submitting

Chicago compliance is the kind of work that takes attention to detail across every page of the document, and even careful writers miss things after weeks of revision. Editor World's academic editing services include Chicago review at the citation, footnote, bibliography, and document-formatting level. The book editing, dissertation editing, and journal article editing services apply the same standard to documents at each level.

Use the instant price calculator to see your cost before committing, or browse available editors to find someone with a background in your specific field.

Frequently Asked Questions About Chicago Style

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