Most citation guides are 50-page PDFs from university libraries. This is the quick-reference version: four styles, side-by-side, with the rules that actually trip students up.

Published: 2026-06-21By: Toolhub Team

Pick a citation style. Any one of them. Now try to remember whether the year goes in parentheses or after a comma, whether multiple authors get all listed or shortened to "et al.," whether the title of a website is italicized or in quotation marks. The answer is different in each style. That's the whole problem with citation guides: they look interchangeable until you submit a paper formatted in the wrong one and get marked down for it.

This is the cheat-sheet version of the four most-required styles, with the rules that actually break student submissions when they're missed. It is not a replacement for the Publication Manual of the American Psychological Association or for the MLA Handbook — those are the authoritative sources. It is a quick-reference covering the 80% of cases that come up in real assignments, plus the most expensive mistakes.

The five citation elements every style cares about

Every citation style is a different way of arranging the same five pieces of information:

  1. Author — who wrote it. Single, multiple, organisation, anonymous.
  2. Year — when it was published. Sometimes month and day too.
  3. Title — what's it called. Article title vs book title vs journal title are formatted differently.
  4. Source / container — where it lives. Journal name, book title, website, broadcast network.
  5. Locator — how to find the specific bit. Page numbers, paragraph numbers, DOI, URL.

The four styles differ in how they punctuate and order these five elements. Once you see the pattern, switching styles becomes a layout exercise, not a memorisation slog.

APA 7 — when required, what changed from APA 6

APA 7 is required by most psychology, education, and nursing programs, plus a growing number of social-science journals. APA 6 was retired in October 2019; if your instructor hasn't updated their handout, ask which version they expect because the differences matter.

Quick-reference format for the most common source types:

The three APA 7 changes most likely to trip students who learned APA 6:

  1. Publisher location dropped. APA 6 required "New York, NY: HarperCollins." APA 7 just says "HarperCollins." This change is the single biggest source of error in transitional papers.
  2. "et al." starts at 3 authors instead of 6. With 3+ authors, the first in-text citation uses the first author plus "et al." right away.
  3. DOI format changed. Use https://doi.org/10.1000/... format. The old "doi:10.1000/..." prefix is wrong in APA 7.

MLA 9 — works cited, in-text, what's new in v9

MLA 9 is the default for literature, language, and most humanities programs. The 9th edition came out in 2021; MLA 8 from 2016 is close enough that older guides usually still work, but MLA 9 added clearer rules for online media and inclusive language.

Quick-reference format:

The three MLA 9 quirks worth knowing:

  1. "Containers" can nest. A journal article on a database (e.g., JSTOR) cites the journal as container 1 and JSTOR as container 2. Don't drop the database when citing from it.
  2. In-text citations use page numbers, not years. "(Smith 47)" not "(Smith 2020)." This is MLA's most distinctive feature and the most common mix-up for students switching from APA.
  3. Day-month-year ordering, not month-day-year. "15 March 2024" not "March 15, 2024."

Chicago — Notes-Bibliography vs Author-Date

Chicago is two styles in one book, which causes confusion. History, philosophy, religion, and most fine-arts programs use Notes-Bibliography (footnotes plus a bibliography). Sciences and social sciences using Chicago use Author-Date (in-text parenthetical citations like APA).

Notes-Bibliography quick-reference:

The three Chicago quirks:

  1. Notes vs bibliography format differs. Same source, different punctuation depending on whether it's in a footnote or in the bibliography. Easy to get the two muddled.
  2. "Ibid." was deprecated in the 17th edition (2017). Use the shortened note format instead.
  3. City of publication still required in Chicago, unlike APA 7 where it was dropped. The two styles look superficially similar but differ on this one rule.

Harvard — the "British APA," with variations

Harvard isn't actually a single defined style. It's a family of author-date styles that emerged in British and Commonwealth universities, most resembling APA but with university-by-university variations. Cambridge, Imperial College London, the University of Manchester, the University of Cape Town, and many Australian universities each publish their own "Harvard guide" with subtle local differences.

The common Harvard pattern:

The Harvard pitfall to know about: your university's specific Harvard guide is the rule, not the generic version. Always check the library handout before submitting. Cambridge's Harvard differs from Imperial's, which differs from Manchester's, in small but graded-on details like the punctuation before "Available at:" and whether the access date is in parentheses.

Common student mistakes across all four styles

Five mistakes that cost marks regardless of which style you're using:

Tool walkthrough

Enter the same source — say, a journal article with two authors, a DOI, and an issue number — into the citation formatter. The tool produces the same source in all four styles simultaneously. Run your eye down the list and notice exactly where they differ. That side-by-side view is the fastest way to internalise the patterns.

For instructors building assessment rubrics that explicitly grade citation accuracy, the rubric generator includes citation-correctness criteria you can drop into a standard essay rubric. The lesson plan template has a placeholder for the required citation style which is worth filling in early — students who guess from the prompt usually guess wrong.

Where to read further

Authoritative sources beyond cheat-sheets:

Citations look like fussy detail work. They are fussy detail work. They're also the lowest-effort easy marks on most academic writing assignments: get the formatting right once and you protect the grade from preventable deductions. Worth the half hour to learn the style your program actually uses.

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