Chicago Style Citation: Author-Date vs Notes-Bibliography Explained
Chicago has two separate citation systems. Here's how to tell which one you need — and how to format both correctly.
Unlike APA or MLA, the Chicago Manual of Style offers two distinct citation systems. Which one you use depends on your discipline — and using the wrong one is a common (and avoidable) mistake.
- Notes-Bibliography (NB): History, arts, humanities — uses footnotes and a Bibliography page
- Author-Date (AD): Sciences and social sciences — uses parenthetical in-text citations and a References page
The Two Chicago Systems at a Glance
| Feature | Author-Date | Notes-Bibliography |
|---|---|---|
| In-text format | (Smith 2023, 45) | Superscript footnote number¹ |
| Used in | Sciences, social sciences | History, arts, humanities |
| Bibliography title | References | Bibliography |
| Year placement | After author in citation | Near end of footnote entry |
| Page number format | (Smith 2023, 45) | In footnote: Smith, Title, 45 |
Quick rule: If your professor says "Chicago" and you're in a history or humanities class, default to Notes-Bibliography. If you're in a science or social science class, use Author-Date.
Chicago Author-Date Format
Author-Date works similarly to APA — parenthetical citations in the text, full entries in a "References" list at the end. The key difference is no comma between author and year in Chicago: (Smith 2023) rather than APA's (Smith, 2023).
Book
In-Text Citation
(Brown 2019, 112)References Entry
Brown, Brené. 2019. Dare to Lead: Brave Work. Tough Conversations. Whole Hearts. New York: Random House.Journal Article
In-Text Citation
(García and Lee 2022, 415)References Entry
García, Maria, and Samuel Lee. 2022. "Social Media and Adolescent Wellbeing." Journal of Youth Research 25 (3): 410–428. https://doi.org/10.1080/13676261.2021.1234567.Website
In-Text Citation
(CDC 2023)References Entry
Centers for Disease Control and Prevention. 2023. "Understanding COVID-19." Accessed November 1, 2023. https://www.cdc.gov/covid19.Chicago Notes-Bibliography Format
Notes-Bibliography uses superscript numbers in the text that correspond to footnotes (at the page bottom) or endnotes (at the document end). Full source details appear in the footnote the first time a source is cited — subsequent citations use a shortened form.
Footnote structure: First citation = full note. Second+ citation = short note (Last Name, Short Title, page). Same source cited consecutively = "Ibid.," page.
Book
First Footnote (full)
1. Brené Brown, Dare to Lead: Brave Work. Tough Conversations. Whole Hearts (New York: Random House, 2019), 112.Subsequent Footnote (short)
2. Brown, Dare to Lead, 45.Bibliography Entry
Brown, Brené. Dare to Lead: Brave Work. Tough Conversations. Whole Hearts. New York: Random House, 2019.Journal Article
First Footnote (full)
3. Maria García and Samuel Lee, "Social Media and Adolescent Wellbeing," Journal of Youth Research 25, no. 3 (2022): 415, https://doi.org/10.1080/13676261.2021.1234567.Subsequent Footnote (short)
4. García and Lee, "Social Media," 415.Bibliography Entry
García, Maria, and Samuel Lee. "Social Media and Adolescent Wellbeing." Journal of Youth Research 25, no. 3 (2022): 410–428. https://doi.org/10.1080/13676261.2021.1234567.Generate Chicago Citations Automatically
Our Chicago citation tool handles both Author-Date and Notes-Bibliography formats — just enter your source details.
Chicago vs Turabian: What's the Difference?
Kate Turabian's A Manual for Writers of Research Papers, Theses, and Dissertations is a student-adapted version of the Chicago Manual of Style. The two are nearly identical in citation format — the difference is scope and audience:
Chicago Manual of Style
- Full professional standard (1,000+ pages)
- Covers all publishing scenarios
- Used in academic publishing and professional writing
Turabian
- Simplified for students (~400 pages)
- Identical citation formats to Chicago
- Used in high school, undergrad, and graduate student papers
If your professor says "Turabian," use Chicago citation format — the rules are the same.
How to Format the Bibliography Page
- •Title: "Bibliography" centered at top (Notes-Bib) or "References" (Author-Date)
- •Hanging indent: First line flush left, subsequent lines indented 0.5 inches
- •Alphabetical order: Sort by author's last name
- •Author format: Last, First for first author; First Last for subsequent authors
- •Title case: Chicago uses headline-style capitalization (Title Case) for titles
- •Spacing: Single-space within entries, double-space between entries (student papers) or use Chicago's own style for professional works
Common Chicago Citation Mistakes
Using the wrong Chicago system
Confirm with your instructor. History courses almost always use Notes-Bibliography. Science courses typically use Author-Date.
Forgetting the short note on second citation
After the first full footnote, subsequent citations of the same source use a shortened form: Last Name, Short Title, page.
Wrong order in bibliography vs footnote
In footnotes, first name comes first (John Smith). In bibliography entries, last name comes first (Smith, John) for alphabetical sorting.
Omitting "Ibid." or short notes
When citing the same source consecutively, use "Ibid." (with page if different). For non-consecutive repeat citations, use the short note form.
Confusing Chicago with Turabian
Turabian is a simplified version of Chicago for students and theses. The formats are nearly identical — Turabian just has slightly simplified rules for student papers.