Chicago Notes-Bibliography vs Author-Date: Which One Do You Use?

Use Notes-Bibliography if you're in history, literature, philosophy, art, or theology. Use Author-Date if you're in the social sciences, economics, or any field that already feels close to APA. Your professor's syllabus overrides everything below.

The two systems in one paragraph each

Notes-Bibliography (NB)

You drop a superscript number in the text, and the citation lives at the bottom of the page as a footnote (or at the end as an endnote). A full bibliography sits at the back of the paper. This system handles archival sources, letters, manuscripts, and weird unpublished material gracefully, which is why humanities fields love it. Note numbers run consecutively through the whole paper.

Author-Date (AD)

You put (Author Year, page) directly in the sentence, and a reference list sits at the back. Same idea as APA, just with slightly different punctuation and capitalization. Cleaner for papers that cite a lot of data, studies, or named researchers, because the year is right there next to the claim.

Both systems pull from the same Chicago Manual of Style (18th edition, 2024), so the underlying source rules (what counts as a journal, how to format an editor, etc.) are identical. Only the display changes.

How to pick if your syllabus doesn't say

Ask three questions:

1. What does my discipline do? History papers almost always use NB. Sociology and political science usually use AD. If your professor trained in the field, they'll expect the field's default.
2. Am I citing a lot of unpublished or primary sources? Letters, interviews, archival boxes, and manuscripts read more naturally as footnotes. NB wins.
3. Am I citing a lot of empirical studies? Author and year matter to your argument ("Smith 2019 found..."). AD wins.

If you're still stuck, NB is the safer default for any humanities course, and AD is safer for any social science course.

Same source, both styles

A journal article by Jane Doe titled "Reading Faulkner" in American Literature, volume 92, issue 3, pages 451 to 470, published 2020.

Notes-Bibliography (footnote, first time):

1. Jane Doe, "Reading Faulkner," American Literature 92, no. 3 (2020): 455.

Notes-Bibliography (shortened footnote, second time):

2. Doe, "Reading Faulkner," 460.

Notes-Bibliography (bibliography entry):

Doe, Jane. "Reading Faulkner." American Literature 92, no. 3 (2020): 451–470.

Author-Date (in-text):

(Doe 2020, 455)

Author-Date (reference list entry):

Doe, Jane. 2020. "Reading Faulkner." American Literature 92 (3): 451–470.

Notice the differences are small but real: in AD, the year moves up next to the author, the journal issue number drops its no., and the bibliography is called a "reference list."

Switching between them

If your professor changes the requirement halfway through a draft, you don't have to rebuild your research. The source information is the same. What changes:

• Position of the year. Move it next to the author (AD) or leave it in the publication slot (NB).
• Footnotes vs in-text. Convert each footnote into a parenthetical, or vice versa.
• Title case vs sentence case. Both systems use title case for English-language book and article titles, so this part actually stays the same. Some older guides claimed AD used sentence case; the current edition does not.
• List heading. "Bibliography" becomes "References."

A generator can flip the same source between the two formats without you re-entering anything.

Common mistakes

• Mixing the two in one paper. Pick one and stay with it. Footnotes plus in-text parentheticals looks chaotic and gets points docked.
• Forgetting the page number in the note or parenthetical. Chicago expects a specific page for any direct quote and for most paraphrases.
• Skipping the bibliography because you used footnotes. Most professors still want both. Check the assignment.
• Confusing AD with APA. They look similar but punctuation and capitalization differ. Don't run an APA generator and call it Chicago.

Quick decision table

When in doubt, email your TA before you start. Five seconds of asking beats five hours of reformatting.

Generate Chicago citations →

Recommended

If you cite often, the manual on your shelf saves a lot of second-guessing.

Publication Manual of the APA, 7th edition (affiliate link — you pay the same price, we earn a small commission).