Choosing a Citation Style: APA, MLA, Chicago, Harvard, IEEE, Vancouver and More

The required style is set by whoever will assess or publish your work. For coursework that is your module handbook or assignment brief. For a thesis it is your graduate school's formatting regulations, sometimes with a departmental preference layered on top. For a journal article it is the journal's author guidelines, which may name a standard style, a modified version of one, or a house style of their own.

Where the requirement is truly open, for example a working paper or a thesis whose regulations only say "a recognized style, applied consistently", choose the style most common in your discipline, because your readers will find it easiest to follow. Consistency matters more than the particular choice: a reference list that mixes conventions looks careless even if every entry is individually defensible.

Always note the edition. APA 6 and APA 7 differ in ways examiners notice, and law and medicine update their guides regularly. The editions described below were current as of September 2026.

Almost every style belongs to one of three families. Author-date styles put the author's surname and year in the text, for example (Nguyen, 2023), and list sources alphabetically at the end. They suit disciplines where the recency of evidence matters, such as psychology, education, business and the social sciences.

Numeric styles put a number in the text, either in square brackets [4] or as a superscript, and list sources in the order they are first cited. They save space and keep the prose uncluttered, which is why engineering, computing and biomedical journals favor them.

Note styles put the citation in a footnote or endnote, often with a bibliography as well. They allow commentary alongside sources and precise pinpointing of pages or archival items, which is why history, some humanities fields and law rely on them. Author-page styles, notably MLA, are a close cousin of author-date: they cite the author and page, such as (Morrison 42), because the page matters more than the year when discussing texts.

The table lists the styles you are most likely to meet and where they are most common. Discipline patterns are tendencies, not rules; a nursing school may use Harvard, and a psychology journal may use a numeric system.

Switching between styles is rarely about the big picture; it is about dozens of small conventions. Reference managers handle many of them automatically, but not all, and they depend on the metadata you feed them.

APA 7 simplified several rules compared with APA 6: no publisher location for books, DOIs formatted as https://doi.org/ links, up to 20 authors listed in the reference entry, and "et al." from the first in-text citation for works with three or more authors. MLA 9 uses the "container" model, so a chapter in an edited book or an article in a database is described by nested containers rather than by source-type templates.

Harvard is the most variable of all. Because no single body owns it, universities publish their own versions that differ in punctuation, the placement of the year and the treatment of online sources. If your university names a guide, use that one exactly rather than a generic Harvard template in your reference manager.

• Capitalization of titles: APA uses sentence case for article and book titles; MLA and Chicago use title case.
• Author names: APA uses initials; MLA and Chicago use full first names where available.
• Ampersand: APA uses "&" inside parentheses and in reference lists; MLA and Chicago use "and".
• Ordering: author-date lists are alphabetical; numeric lists follow order of first citation.
• Page numbers: required for quotations in APA and Harvard; always part of the citation in MLA; pinpoints in footnotes for Chicago and legal styles.
• Journal names: IEEE, Vancouver and AMA abbreviate journal titles; APA and MLA give them in full.
• Legal sources: OSCOLA and the Bluebook have detailed rules for cases, statutes and treaties that general styles barely cover.

Look at the five or six journals you cite most often and see what they use. If they cluster around one style, that is your discipline's working norm and your readers will expect it. Interdisciplinary projects can pick the style of the field whose readers are primary; a public-health thesis in a medical school would usually lean toward Vancouver or AMA, while one in a social-science faculty would lean toward APA or Harvard.

Consider the kind of sources you use. Archival materials, manuscripts and sources needing commentary fit a notes system. Rapidly updated empirical literature fits author-date. Very long reference lists in technical documents fit numeric systems, which keep the text readable.

Think ahead to publication. If chapters of a thesis will become journal articles, using the style of your likely target journals now reduces later reformatting, though a good reference manager makes switching almost painless.

Seeing the same reference formatted in several styles makes the differences concrete. The source below is invented for illustration: a journal article by Amina Rahman and Tomás Ortega, published in 2023 in the Journal of Learning Analytics, volume 10, issue 2, pages 45 to 61, with a DOI.

Notice how much changes: the order of elements, name format, capitalization of the article title, italics, the presentation of volume and issue, and whether the DOI appears as a link. A reference manager produces these automatically, but only if the record lists the correct authors, item type and journal name.

Some sources do not fit neatly into standard templates. Secondary citation, where you cite a work you only know through another author, should be used sparingly; APA, for example, asks you to name the original in text and list only the source you actually read. Where possible, locate and read the original instead.

Datasets, software, preprints, government reports, policy documents and standards all have specific formats in the major manuals, and reference managers support them if you choose the correct item type. Preprints should be updated to the published version if one appears before your submission. For generative AI tools, APA, MLA and Chicago have each published guidance on how to cite or acknowledge them, and many institutions add their own disclosure requirements; follow your institution first.

Legal and archival materials are the most demanding. If you cite cases, legislation or treaties in a non-law discipline, check whether your style has a section on legal sources or whether your department expects OSCOLA or Bluebook conventions for those items only.

Zotero, Mendeley and EndNote all store your sources and output citations in any style defined in the Citation Style Language (CSL) or, for EndNote, its own style files. The output is only as good as the stored data: missing issue numbers, all-caps titles from a database export, or a conference paper filed as a journal article will all produce wrong references regardless of the style chosen.

Good practice is to import records from DOIs or databases rather than typing them, check each record's item type and fields when you add it, choose the exact style variant your institution or journal requires, and use the word-processor plug-in so that citations update if you change style. Before submission, refresh the bibliography and read the reference list once by eye, because automated styles still mishandle edge cases such as corporate authors, translated works and legal materials.

If your library is messy or you need a custom university Harvard style, a reference manager setup session can save hours before a deadline.

Switching is simplest when every citation was inserted through a reference manager. Change the style in the plug-in, refresh, and then check the items that styles treat differently: sentence versus title case, abbreviated journal names, "et al." thresholds, and the handling of secondary citations.

If your citations were typed manually, switching from author-date to numeric is the hardest move, because you must number sources in order of first appearance and replace every in-text citation. Budget real time for it, or convert your manual citations into reference-manager citations first. Also remember that footnote styles change the text itself: sentences that name authors may need rewording once the citation moves to a note.

Beyond the reference list, the way citations sit in your sentences affects readability and signals academic maturity. Author-date styles allow two forms: parenthetical, where the citation follows the claim, and narrative, where the author becomes part of the sentence, as in "Rahman and Ortega (2023) found that...". Use narrative citations when the author or study itself matters to your point, and parenthetical citations when the finding matters more than who produced it.

Avoid long strings of citations after trivial claims and, conversely, uncited claims about specific findings. When several sources support one statement, order them as your style requires (alphabetically in APA, often chronologically or by relevance in others) and consider whether all of them are needed. In numeric styles, place the number immediately after the relevant claim or author name rather than at the end of a long sentence covering several ideas, so readers know which source supports what.

Page or paragraph locators are required for direct quotations in most styles and recommended for paraphrases of specific passages. Examiners checking a surprising claim will look for the exact location, and providing it builds trust in your use of sources.

Run through these checks before any assessed or published submission. They take less than an hour for a typical thesis chapter and catch the problems markers and editors notice most.

• Every in-text citation has a matching reference entry, and every reference is cited at least once.
• Names, years and spellings match between text and list.
• The required edition of the style is followed, not an older one saved in your reference manager.
• DOIs are present and correctly formatted where the style requires them.
• Direct quotations have page or paragraph locators.
• Secondary citations (sources you did not read yourself) are cited as the style requires.
• Reference list ordering follows the style: alphabetical or numeric.
• Formatting such as hanging indents and italics is applied consistently.