Chicago Citation Style Guide: Notes-Bibliography and Author-Date Systems (2026)
The Chicago citation style guide covers one of the most comprehensive and flexible referencing systems used in academic writing. Published by the University of Chicago Press, the Chicago Manual of Style (CMOS) is used in history, arts, religion, social sciences, and many humanities disciplines. Unlike APA or MLA, Chicago operates through two distinct systems — Notes-Bibliography (NB) for humanities and Author-Date (AD) for sciences and social sciences — and this guide explains both, with examples for every common source type updated to 2026.
The Chicago Manual of Style is now in its 18th edition (2024), which introduced several updates: ibid. is now generally discouraged in favour of shortened citations, further guidance on AI tools was added, and clarifications were made for digital-first sources. This guide reflects all current 2026 requirements and clearly marks where CMOS 18th edition differs from the 17th.
Notes-Bibliography vs Author-Date: When to Use Which
| Feature | Notes-Bibliography (NB) | Author-Date (AD) |
|---|---|---|
| Common in | History, literature, arts, religion, philosophy | Natural sciences, social sciences, some education |
| In-text marker | Superscript number¹ | (Author Year, page) |
| Full citation location | Footnote or endnote | Reference list |
| End-of-paper list | Bibliography | References |
| Allows commentary in notes | Yes — footnotes can contain discursive notes | No |
Notes-Bibliography System: Full Guide
How In-Text Markers Work
Place a superscript number immediately after the punctuation of the sentence or clause that contains the cited material: “Colonial planners used built space to inscribe racial hierarchies into the urban environment.¹” The number corresponds to a footnote at the bottom of the page (or endnote at the end of the chapter/paper).
Footnote Format (First Full Citation)
The first time you cite a source, give the full citation in the footnote:
¹ Edward W. Said, Orientalism (New York: Pantheon Books, 1978), 45.
Note the format: First Name Surname, Title (Place: Publisher, Year), page.
Shortened Citation (Subsequent References)
After the first full citation, use a shortened form: Surname, Shortened Title, page.
⁵ Said, Orientalism, 112.
CMOS 18th edition update: The 17th edition recommended using “Ibid.” for consecutive references to the same source. CMOS 18th edition now discourages ibid. in favour of the shortened citation form, as shortened citations are clearer when text is rearranged.
Bibliography Entry (NB)
The bibliography at the end of the paper uses a different format from footnotes: Surname, First Name. Title. Place: Publisher, Year.
Said, Edward W. Orientalism. New York: Pantheon Books, 1978.
Author-Date System: Full Guide
In-Text Citations (AD)
Author-Date in-text citations look similar to APA: (Author Year, page). The comma separates the year and page.
| Scenario | Chicago AD Format |
|---|---|
| 1 author, paraphrase | (Smith 2023) |
| 1 author, direct quote | (Smith 2023, 45) |
| 2 authors | (Smith and Jones 2023) |
| 3+ authors | (Smith et al. 2023) |
| Organisation author | (NHS England 2023) |
| No author | (Shortened Title 2023) |
Reference List Entry (AD)
Smith, Anna B., and Charles D. Jones. 2022. Research Methods in Social Science. 4th ed. London: Sage.
Note the year moves immediately after the author’s name — this is the key visual difference from the NB bibliography entry.
Books (Both Systems)
Whole Book — NB Footnote
¹ Homi K. Bhabha, The Location of Culture (London: Routledge, 1994), 121.
Whole Book — NB Bibliography
Bhabha, Homi K. The Location of Culture. London: Routledge, 1994.
Chapter in Edited Book — NB Footnote
³ Homi K. Bhabha, “Of Mimicry and Man: The Ambivalence of Colonial Discourse,” in The Location of Culture (London: Routledge, 1994), 121–31.
Chapter in Edited Book — NB Bibliography
Bhabha, Homi K. “Of Mimicry and Man: The Ambivalence of Colonial Discourse.” In The Location of Culture, 121–31. London: Routledge, 1994.
Journal Articles (Both Systems)
Journal Article — NB Footnote (with DOI)
⁴ Amy Orben and Andrew K. Przybylski, “The Association between Adolescent Well-Being and Digital Technology Use,” Nature Human Behaviour 3, no. 2 (2019): 173, https://doi.org/10.1038/s41562-018-0506-1.
Journal Article — NB Bibliography
Orben, Amy, and Andrew K. Przybylski. “The Association between Adolescent Well-Being and Digital Technology Use.” Nature Human Behaviour 3, no. 2 (2019): 173–82. https://doi.org/10.1038/s41562-018-0506-1.
Journal Article — AD Reference List
Orben, Amy, and Andrew K. Przybylski. 2019. “The Association between Adolescent Well-Being and Digital Technology Use.” Nature Human Behaviour 3 (2): 173–82. https://doi.org/10.1038/s41562-018-0506-1.
Websites and Online Sources
Website — NB Footnote
⁵ World Health Organization, “Mental Health: Strengthening Our Response,” May 5, 2023, https://www.who.int/news-room/fact-sheets/detail/mental-health-strengthening-our-response.
Website — NB Bibliography
World Health Organization. “Mental Health: Strengthening Our Response.” May 5, 2023. https://www.who.int/news-room/fact-sheets/detail/mental-health-strengthening-our-response.
Note: Unlike APA and MLA, Chicago NB bibliography entries may include an “Accessed” date for sources likely to change: “Accessed April 8, 2026.”
Citing AI Tools in Chicago Style
NB Footnote for AI-Generated Text
⁶ Text generated by ChatGPT (OpenAI, March 2026), in response to the prompt “Explain the Chicago Notes-Bibliography system.”
NB Bibliography Entry for AI
ChatGPT. “Explain the Chicago Notes-Bibliography system.” Response to prompt by [Author Name]. OpenAI, March 2026. https://chat.openai.com.
CMOS 18th edition added guidance on AI citations in 2024. The recommended approach is to describe the AI-generated content in notes (NB) or reference list (AD) and to disclose AI use in a method note or acknowledgements section. Always check your institution’s current AI use policy.
Key Changes in CMOS 18th Edition (2024)
| Change | CMOS 17th | CMOS 18th |
|---|---|---|
| Ibid. | Recommended for consecutive references | Discouraged; use shortened citation instead |
| AI citation | No specific guidance | Dedicated section on citing LLMs and AI tools |
| Place of publication | Required for book citations | Required for print books; optional for digital-only |
| Inclusive language | General guidance | Expanded chapter on gender-neutral and person-first language |
Chicago vs APA vs MLA: Side-by-Side
| Feature | Chicago NB | APA 7th | MLA 9th |
|---|---|---|---|
| In-text marker | Superscript number | (Author, Year) | (Author Page) |
| End list name | Bibliography | References | Works Cited |
| Place of publication | Required for books | Not required | Not required |
| Discursive notes | Yes (footnotes) | Limited | No |
| Primary field | History, humanities | Social sciences, health | Literature, languages |
For the complete APA rules, see our APA citation format guide. For MLA, see our MLA format guide 2026. For Harvard referencing (common in UK universities), see our Harvard referencing guide. For your dissertation’s full structure context, see our dissertation writing guide.
Tesify’s Auto Bibliography generates correctly formatted Chicago NB and Chicago AD citations from a URL, DOI, or ISBN. Try it free.
Frequently Asked Questions
What is the difference between Chicago footnotes and endnotes?
In Chicago NB style, citations can appear as footnotes (at the bottom of each page) or endnotes (collected at the end of the chapter or paper). Both use the same citation format — the only difference is placement. Footnotes are more reader-friendly since the citation is immediately visible; endnotes reduce page clutter. Most academic journals and some disciplines prefer footnotes; some books use endnotes. Unless your instructor or publisher specifies otherwise, footnotes are the standard choice for student papers.
Can I mix the Chicago NB and Author-Date systems in the same paper?
No. The Notes-Bibliography and Author-Date systems are mutually exclusive. You must choose one and apply it consistently throughout the entire paper. If you are unsure which system to use, check your department’s requirements or ask your instructor. History, humanities, and arts generally use NB; natural and social sciences generally use AD. Some interdisciplinary fields allow either — in which case, choose the system most common in your primary literature and apply it consistently.
Is Chicago style used in the UK?
Yes, Chicago style is used in UK universities, particularly in history, archaeology, philosophy, and theology departments. It is also used by many UK academic publishers and journals in the humanities. However, it is less universally dominant in the UK than in the US — many UK history and humanities departments use their own variants or recommend “Oxford referencing” (which is similar to Chicago NB). Always check your institution’s specific guidelines, as UK practice varies more widely than in the US.
What is the difference between Chicago and Turabian?
Turabian is a student-focused guide based on Chicago, written by Kate Turabian (A Manual for Writers of Research Papers, Theses, and Dissertations, now in its 9th edition). It covers the same two systems (NB and AD) with adaptations for student papers, including guidance on thesis and dissertation formatting. Chicago is the full professional style guide; Turabian is essentially Chicago simplified for students. If your institution specifies Turabian, the citation formats are nearly identical to Chicago — the differences relate mainly to paper formatting, title pages, and dissertation-specific conventions.
Should I still use “ibid.” in Chicago style?
CMOS 18th edition (2024) now discourages the use of ibid. and recommends using shortened citations instead. For example, instead of “Ibid., 45” for a second consecutive reference to Said’s Orientalism, write “Said, Orientalism, 45.” Shortened citations are clearer when documents are rearranged (ibid. can become ambiguous if notes are reordered). If your institution or instructor requires CMOS 17th edition formatting, ibid. is still acceptable for consecutive references to the same source — but check which edition is current practice in your department.
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