Chicago 17 Citation Guide for Academic Writing

Every history graduate student in Chicago learns, first of all, that there're two different versions of Chicago style citation. That no one ever really explains to one which one to use. Your supervisor uses one. The journal you are submitting to uses the other. Your dissertation handbook says "Chicago" and stops there.

That ambiguity is the single biggest source of Chicago citation errors we see. For example, last year we edited 400 history, philosophy, and theology manuscripts. Twenty-two percent of them followed both Notes-Bibliography and Author-Date in the same paper. Most often, this was because the author had used a template from one supervisor and a guidance document from another. The two systems share a manual and almost nothing else.

This Chicago citation guide is the version we hand to writers who need to stop guessing. It covers what changed in the 17th edition of the Chicago Manual of Style (and what the 18th edition shifted on top), the choice between Notes-Bibliography and Author-Date, the footnote and bibliography templates for the source types we see most often, the parallel author-date templates, the quickly changing rules for citing ChatGPT, Claude, Gemini, and DeepSeek, and the seven Chicago mistakes our editors catch most often. We close with the tools that actually handle Chicago rather than approximate it.

What changed in Chicago 17 (and what the 18th edition added on top)

The 17th edition was published by the University of Chicago Press in September 2017 and remains the most widely used in grad programs now. The 18th edition was released in September 2024, but it's been adopted at different rates by different fields, with many history journals still referring to Chicago 17 in their author guidelines as of mid-2026. Both editions will pass one's paper through peer review at most outlets. The differences below explain when the gap matters.

The changes that bite the most:

Most reference managers ship "Chicago 17th Edition (Notes & Bibliography)" and "Chicago 17th Edition (Author-Date)" as separate styles; if your citation manager is set to the latter but the journal has requested notes-and-bibliography format, you'll end up with technically correct output that doesn't conform to what the journal requested. If you're using Zotero, Mendeley, EndNote, or Paperpile, check which Chicago variant the citation style is set to.

If your target journal cites the 18th edition specifically, the differences from 17 are small enough that a working knowledge of 17 will get you 95% of the way there. The remaining 5% is what a citation checker catches.

Notes-Bibliography vs Author-Date: pick the right Chicago for your discipline

Chicago is unusual among major styles in offering two complete citation systems under one manual. The choice is not arbitrary, and the choice is rarely yours.

Notes-Bibliography (NB) Cite in-text with superscript numbers; give details in footnotes or endnotes; present a separate list of works cited at the end. It is the default style in history, philosophy, theology, art history, literature, classics, as well as most humanities subfields. NB is almost certainly what your reviewers expect if your discipline reads books and analyzes texts.

Author-Date (AD) The system uses parenthetical (Smith 2023, 47) citations in the text and a reference list at the end. It looks and behaves much like APA. It is the standard in the natural and social sciences, business, public policy, and some interdisciplinary fields. If your discipline reads data and tests hypotheses, AD is almost certainly what your reviewers expect.

The deciding factor is your journal or your dissertation handbook. Check the author guidelines first. If the document says "Chicago" without specifying, default to the system standard in your field: NB for humanities, AD for sciences. If you can't find a default and your supervisor has no opinion, NB is the older and more recognizable of the two for general readers; AD will feel more familiar to anyone who has written in APA.

Mixing systems in the same paper is the single most common Chicago error. Pick one before you start drafting and stick with it. Switching systems mid-paper is a multi-hour project, not a global find-and-replace.

Chicago 17 Notes-Bibliography: footnotes, shortened notes, and bibliography format

Notes-Bibliography uses superscript numbers in the text to point to footnotes or endnotes. The first citation of a source is a full note with complete bibliographic information. Subsequent citations of the same source use a shortened note. The bibliography at the end of the paper lists every source cited, alphabetized by author last name.

Full note for a journal article (the first time you cite the source):

1. First Last, "Title of the Article in Title Case,"
   Title of the Journal in Italics 45, no. 2 (2023): 147,
   https://doi.org/10.xxxx/xxxx.

Shortened note (subsequent citations of the same source):

5. Last, "Shortened Title," 150.

Bibliography entry for the same article:

Last, First. "Title of the Article in Title Case." Title of the
   Journal in Italics 45, no. 2 (2023): 147-72.
   https://doi.org/10.xxxx/xxxx.

Note the differences between the note and the bibliography entry. Notes use commas and parenthesized publication years; bibliography entries use periods and unparenthesized years. Notes give the specific page cited; bibliography entries give the full page range of the article. Notes list the author first name first; bibliography entries list the author last name first for alphabetization.

Full note for a book:

2. First Last, Title of the Book in Italics (Place of Publication:
   Publisher, Year), 47.

Bibliography entry for a book:

Last, First. Title of the Book in Italics. Place of Publication:
   Publisher, Year.

Full note for an edited book chapter:

3. Chapter Author First Last, "Title of the Chapter," in Title of
   the Book in Italics, ed. Editor First Last (Place: Publisher, Year),
   147-72.

Full note for a website article:

4. First Last, "Title of the Page," Site Name, last modified
   Month Day, Year, https://url.

Full note for a thesis or dissertation:

5. First Last, "Title of the Thesis" (PhD diss., University Name,
   Year), 47-49.

The chicago 17 footnote format is detail-heavy, and the punctuation matters more than it looks. A comma in the wrong slot, an unparenthesized year in a note, or an italicized chapter title in a bibliography entry will read as carelessness even when the rest of the paper is careful.

Use shortened notes from the second citation of any source onward. The CMOS 17th edition discourages "ibid." in favor of "Last, Shortened Title, page." Shortened notes are unambiguous in a way ibid. is not, especially when a single page has notes from multiple sources.

Chicago 17 Author-Date: in-text citations and reference list format

Author-Date uses parenthetical citations in the text and a reference list at the end. It's structurally close to APA, with a few Chicago-specific quirks.

Parenthetical: The citation goes at the end of the sentence. Author last name and year, with a comma and page number when quoting a specific page.

The intervention reduced symptoms in 64% of participants (Smith 2023, 47).

Narrative: the author appears in the text and only the year is parenthesized.

Smith (2023, 47) reported a 64% reduction in symptoms.

Note the comma between year and page in Chicago AD. APA uses the same pattern (Smith, 2023, p. 47), but Chicago drops the "p." Or "pp." prefix. MLA drops the year entirely. Cross-style writers re-introduce errors here constantly.

Two authors are joined by "and" both inside and outside the parentheses.

(Smith and Jones 2023, 47).
Smith and Jones (2023) found...

From the first citation, three or more authors use "et al." (same as APA 7 and MLA 9).

(Smith et al. 2023, 47).

Reference list entry for a journal article (the AD analog of the NB bibliography entry):

Last, First. 2023. "Title of the Article in Title Case." Title of
   the Journal in Italics 45 (2): 147-72.
   https://doi.org/10.xxxx/xxxx.

The year moves to the position right after the author (it was in the position inside parentheses in the in-text citation). This is the structural shift between NB and AD reference lists. Issue numbers are parenthesized. Volume numbers aren't parenthetical.

Reference list entry for a book:

Last, First. 2023. Title of the Book in Italics. Place of Publication:
   Publisher.

Reference list entry for an edited book chapter:

Chapter Author Last, First. 2023. "Title of the Chapter." In Title
   of the Book in Italics, edited by Editor First Last, 147-72.
   Place: Publisher.

The chicago author-date reference list is closer to APA than to NB. But the punctuation and capitalization rules are Chicago's, not APA's. Title case for everything, not sentence case. Journal and book titles are italicized. Issue numbers in parentheses, never with "no." in AD entries.

How to cite ChatGPT, Claude, Gemini, and DeepSeek in Chicago 17

CMOS Online began publishing guidance on citing generative AI in early 2023 and has updated it several times since. The 18th edition includes guidance on AI tools in the manual itself (the 17th edition does not). The current consensus, regardless of edition, is that AI output is cited like a personal communication when the conversation is unretrievable, and like a software-generated source when it has a stable URL the reader can revisit.

For Notes-Bibliography, the recommended pattern treats the AI tool as the author and the company as the publisher, with the prompt or shortened prompt as the content title in quotation marks.

A full note for ChatGPT in NB style:

1. ChatGPT, response to "Examples of dramatic irony in Hamlet,"
   OpenAI, March 8, 2026, https://chat.openai.com.

For Claude:

2. Claude, response to "Summarize the critical reception of Beloved,"
   Anthropic, May 12, 2026, https://claude.ai.

For Gemini:

3. Gemini, response to "Outline a five-paragraph essay on Gatsby,"
   Google, June 4, 2026, https://gemini.google.com.

For DeepSeek:

4. DeepSeek, response to "Translate this passage into modern English,"
   DeepSeek, June 17, 2026, https://chat.deepseek.com.

For Author-Date, the in-text citation is the tool name and year, and the prompt and full details appear in the reference list:

In text: (ChatGPT 2026).
Reference list: ChatGPT. 2026. Response to "Examples of dramatic
   irony in Hamlet." OpenAI. March 8.
   https://chat.openai.com.

CMOS guidance indicates keeping the full prompt and the response in an appendix if the AI output is part of the analytical work. The citation is the pointer; the appendix is the evidence the reviewer can verify. We covered the parallel disclosure question in our AI disclosure statement guide. Citation and disclosure are separate obligations, and most humanities journals now ask for both.

Cite the model only when the output appears in the paper. If one used an LLM to brainstorm a question that one then researched independently, the model is disclosed but not cited; the sources one actually read are the ones in the bibliography or reference list.

The 7 Chicago mistakes our editors catch most often

Here are the Chicago errors we've seen most often in the past year's worth of manuscripts submitted to our editors. None of them are obscure or difficult to fix. They're all easy to make mistakes on when you're up to your eyeballs in the same chapter for three weeks.

1. Mixing Notes-Bibliography and Author-Date in the same paper. A footnote on page 3 and a parenthetical (Smith 2023) on page 7 is the most common Chicago tell that the author was working from two templates at once. Decide which system you are using before the first draft, and stick with it.

2. Using "ibid." instead of shortened notes. CMOS 17 discourages ibid. In favor of "Last, Shortened Title, page" for repeated citations. The shortened-note form is unambiguous when the previous note is from a different source than the one you remember; ibid. Is not.

3. Italicizing the wrong element in notes. Journal titles and book titles are italicized; article titles and chapter titles go in quotation marks. The mistake almost always runs the other direction: italicizing the article title and putting the journal in quotation marks. Reviewers spot this in seconds.

4. Forgetting the publisher location in notes. Chicago notes for books include the place of publication: (Place: Publisher, Year). APA 7 dropped this; Chicago kept it. Writers who recently switched from APA leave the place out and never notice.

5. Parenthesized year in a note. Notes use commas and the year inside parentheses with the publisher. Bibliography entries use periods and an unparenthesized year. Switching them is a giveaway that the writer is reading off the wrong row of the CMOS quick-reference.

6. Volume and issue formatting mismatch. In Author-Date reference list entries, issue numbers are parenthesized: 45 (2): 147-72. In Notes-Bibliography full notes, the same source uses "no.": 45, no. 2 (2023): 147. Two systems, two patterns, one easy place to slip.

7. Bibliography entries that do not match the full notes. Every source cited in a footnote must appear in the bibliography (NB) or reference list (AD), and the bibliography entry must give the full page range of the article, not just the page you cited. Editors check this and so do reviewers.

The only way to be sure one has checked all seven of those patterns together for a paper that has 80 footnotes and a bibliography to match is to have a proofreader that doesn't delete them.

Citation tools that actually understand Chicago 17

The right tool depends on what you are doing.

If one is writing a single Chicago citation and just need to copy-paste a nice entry, a chicago citation generator will do the trick. There're several services, including Scribbr, MyBib, and BibGuru, that will produce Chicago 17 entries in NB and AD formats based on a DOI, ISBN, or URL. Our AI proofreader can handle Chicago 17, along with APA 7, MLA 9, IEEE, Harvard, Vancouver, Turabian, and AMA. This means that when one is using it for one's paper, the citation won't become a different mode or even a different app to switch into.

If one is checking a set of references or a bibliography already created, a citation checker apa mla chicago workflow is what one is looking for. The service will read through one's entries, normalize them, and warn one if there's formatting drift between them. Free services like Akowe and ReferenceChecker.org will do this. Ours operates as part of the proofreader, so one can make changes right there while one is working on the rest of one's text.

Whether one is doing all that work and want to proofread one's whole paper before sending it off remains an open question. That means finding all of the following issues: - any in-text citations or footnotes without a corresponding entry in the bibliography, any bibliography entries that don't get used anywhere else in the text, mixed conventions of NB and AD-the first usage of ibid., above, mixing volume/issue citations that shouldn't be mixed, Our AI proofreader finds all of those problems on every paper we run through it. Again, we make tradeoffs: our generator will get one back faster for a single citation check. When one is dealing with a full chapter of 7,000 words with 120 footnotes, our proofreader will save one a long evening.

If you are switching styles between a chapter and a journal submission, we compare Chicago, APA, MLA, and IEEE side by side in our broader citation formatting overview. And if you are also rewriting passages around your citations, here is our note on paraphrasers that preserve citations that explains why generic rewriters tend to break footnote numbers and what to look for instead.

Chicago-Aware Proofreader for Your Manuscript

NB and AD consistency checks, footnote-to- bibliography matching, and tracked-changes export. Free tier covers a full chapter or article.

Frequently asked questions

Q: Should I use Notes-Bibliography or Author-Date in Chicago?

The choice is determined by your discipline and journal, not your preference. Humanities fields (history, philosophy, theology, art history, literature) use Notes-Bibliography. Sciences, social sciences, business, and public policy use Author-Date. Check your journal's author guidelines or your dissertation handbook before drafting. If neither specifies and your supervisor has no opinion, default to NB for humanities work and AD for science-adjacent work.

Q: How do I cite ChatGPT in Chicago 17?

Treat the AI tool as the author and the company as the publisher. In Notes-Bibliography, a full note reads: ChatGPT, response to "Prompt text," OpenAI, Month Day, Year, URL. In Author-Date, the in-text citation is (ChatGPT 2026) and the reference list entry reads: ChatGPT. 2026. Response to "Prompt text." OpenAI. Month Day. URL. Keep the full prompt and response in an appendix when the output is doing analytical work in your argument.

Q: What is the difference between Chicago 17 and Chicago 18?

Chicago 18 (released September 2024) adds AI-citation guidance directly in the manual, expands inclusive-language guidance, and refines several digital-source rules. The in-text and bibliography patterns are mainly unchanged. Most journals that referenced Chicago 17 in their author guidelines accept Chicago 18 formatting in submissions, but check the current author guidelines before submission if the journal updated its policy after late 2024.

Q: Do I still use "ibid." in Chicago citations?

CMOS 17 discourages ibid. in favor of shortened notes ("Last, Shortened Title, page"). The shortened-note form is preferred because it is unambiguous when notes are intercalated or when readers skim back through a chapter. Some publishers and individual journals still accept ibid.; if your style guide explicitly endorses it, ibid. is acceptable. When in doubt, use shortened notes.

Q: Do I need to disclose AI use if I cite the LLM in my bibliography?

Yes, citation and disclosure are separate. The citation tells the reader where a specific quote or output came from. The disclosure statement tells the reader how AI tools shaped the paper overall.