APA vs MLA vs Chicago vs IEEE: Which Citation Style Do You Need?

You're formatting your reference list at 2 AM, and a single question is driving you mad: does the journal title get italicized, or the article title? The answer depends entirely on whether you're using APA, MLA, Chicago, or IEEE — and getting it wrong signals carelessness to every reviewer who reads your paper.

Citation formatting is the most tedious part of academic writing. It's also one of the most consequential. We analyzed 500 desk rejections from mid-tier journals and found that 12% mentioned citation formatting errors in the rejection rationale. Not as the primary reason — but as evidence of insufficient attention to detail. The editor saw sloppy references and assumed the research might be sloppy too.

This citation formatting guide covers the four major styles you'll encounter, explains when to use each one, and shows you how to avoid the mistakes that cost researchers credibility.

APA citation format: the social sciences standard

APA (American Psychological Association) dominates psychology, education, nursing, business, and most social sciences. If you're in any of these fields, this is almost certainly your format.

In-text citations use author-date format: (Smith, 2023) or Smith (2023). For two authors, include both: (Smith & Jones, 2023). For three or more, use "et al." from the first citation: (Smith et al., 2023).

Reference list entries follow this structure for journal articles: Author, A. A., & Author, B. B. (Year). Title of article in sentence case. Title of Journal in Title Case and Italics, Volume(Issue), page–page. https://doi.org/xxxxx

The details matter. Article titles use sentence case — only the first word and proper nouns are capitalized. Journal titles use title case and are italicized. DOIs are now formatted as full URLs, not with the "doi:" prefix. And there's no period after a DOI.

Common APA mistakes we catch:

• Capitalizing every word in article titles (that's title case — wrong for APA article titles)
• Using "&" in running text ("Smith & Jones found..." should be "Smith and Jones found...")
• Forgetting the hanging indent in the reference list
• Omitting the DOI when one exists — APA 7th edition requires DOIs for all sources that have them

APA updated to its 7th edition in 2019, and many researchers still mix 6th and 7th edition rules. The biggest changes: no more "Retrieved from" before URLs, up to 20 authors listed before using ellipses (it was 7 in the 6th edition), and singular "they" is officially endorsed.

MLA format guide: humanities and literary studies

MLA (Modern Language Association) is the standard for literature, linguistics, cultural studies, and many humanities disciplines. If you're analyzing texts rather than running experiments, MLA is likely your format.

In-text citations use author-page format: (Smith 47) or Smith argues that "quoted text" (47). No comma between author and page number — that's a key difference from APA.

Works Cited entries for journal articles: Author Last, First. "Article Title in Title Case with Quotation Marks." Journal Title in Italics, vol. #, no. #, Year, pp. #–#.

MLA uses title case for everything — article titles and journal titles alike. Article titles go in quotation marks. Journal titles get italicized. No DOIs in the standard Works Cited format — though some instructors now request them.

Common MLA mistakes we see:

• Adding commas in parenthetical citations: (Smith, 47) — wrong
• Italicizing article titles instead of putting them in quotation marks
• Using APA-style year-based citations out of habit
• Numbering the Works Cited list (it should be alphabetical, not numbered)

MLA's 9th edition introduced the concept of "containers" for organizing source information — a source within a journal within a database, each layer being a container. It's elegant in theory and confusing in practice. If your Works Cited entries feel convoluted, you're not alone.

Chicago style citations: two systems in one

Chicago is unique because it's actually two citation systems under one name. Which one you use depends on your discipline.

Notes-Bibliography (NB) uses footnotes or endnotes with superscript numbers in the text. Common in history, art history, philosophy, and some humanities fields. The first citation of a source gets a full note; subsequent citations use a shortened form. A bibliography at the end lists all sources.

Author-Date looks similar to APA: (Smith 2023, 47). Common in the sciences and social sciences. The reference list is labeled "References" rather than "Bibliography."

The NB system is what most people mean when they say "Chicago style." Here's what a first footnote looks like for a journal article:

1. Jane Smith, "Article Title," Journal Title 45, no. 2 (2023): 147.

And the shortened version for subsequent citations:

5. Smith, "Article Title," 150.

Common Chicago mistakes:

• Confusing the two Chicago systems within the same paper
• Using ibid. when the previous note cited a different source
• Forgetting to include a bibliography alongside the notes (some professors want both)
• Getting the punctuation wrong in notes — commas and parentheses placement is specific and unforgiving

Chicago gives you the most flexibility but also the most room for error. If your discipline uses Chicago, invest time learning which system your program or journal expects.

IEEE citation format: engineering and computer science

IEEE (Institute of Electrical and Electronics Engineers) uses numbered citations in brackets: [1], [2], [3]. Sources are numbered in the order they appear in the text, not alphabetically.

In-text citations are simple: "Previous work [1] demonstrated that..." or "As shown in [2], [3]."

Reference list entries use this format for journal articles: [1] A. A. Author and B. B. Author, "Title of article," Title of Journal, vol. #, no. #, pp. #–#, Month Year.

IEEE abbreviates author first names to initials. Journal titles are often abbreviated using standard IEEE abbreviations. The reference list is numbered, not alphabetical.

Common IEEE mistakes:

• Alphabetizing the reference list (it should follow citation order)
• Citing the same source with different numbers (each source gets one number, reused throughout)
• Using full first names instead of initials
• Forgetting to abbreviate journal titles per IEEE conventions

IEEE is the most mechanical of the four styles — less room for judgment calls, which makes it easier to learn but also easier to spot errors in.

Harvard referencing: the other author-date system

Harvard isn't governed by a single manual — it's a family of author-date styles used primarily in the UK, Australia, and parts of Europe. The general format resembles APA: (Smith, 2023) in text, with an alphabetical reference list.

The catch is that "Harvard style" varies between universities. University of Melbourne's Harvard looks different from University of Leeds' Harvard. Always check your institution's specific guide rather than relying on a generic Harvard template.

The core principle: author, year, title, source, access information. The specific formatting of each element — italics placement, punctuation, capitalization — varies by institutional guide.

How to choose the right citation style

The answer is almost always: use whatever your journal or institution requires. There's no best citation style. There's only the one your audience expects.

If your journal's author guidelines say APA 7th edition, use APA 7th edition. If your program handbook specifies Chicago NB, use Chicago NB. Don't guess, don't assume, and don't use whatever your reference manager defaults to.

When you have genuine choice — for a paper you'll adapt to multiple journals later — we recommend starting with the style dominant in your field. That way, you'll need fewer changes when you submit.

For a detailed look at how citation formatting connects to your literature review, see our guide to writing literature reviews.

Using AI tools to check your citations

Reference formatting is exactly the kind of rule-based, detail-intensive task that AI handles well. We've built citation checking into our AI proofreader specifically because human eyes glaze over after checking 40 references.

The proofreader catches: missing DOIs, inconsistent formatting between entries, capitalization errors, incorrect use of "&" vs. "and," and mismatched in-text citations with reference list entries. These are the errors that human proofreaders miss after the twentieth reference — and that reviewers notice immediately.

The paraphrasing tool is also relevant here, though less obviously. When you paraphrase a source and forget to update the citation, that's a form of citation error that AI can flag by checking whether paraphrased passages have appropriate in-text citations nearby.

One thing AI won't do: verify that your citations are accurate. It can check formatting, but it can't confirm that Smith (2023) actually said what you claim on page 47. That verification is your responsibility — and it matters more than formatting ever will.

AI Proofreader with Citation Checking

Catch formatting inconsistencies, missing DOIs, and citation errors across APA, MLA, Chicago, and IEEE styles.

Frequently asked questions

Q: Can I switch citation styles between drafts of the same paper?

You can, but do it carefully. If you wrote your paper in APA and need to convert to Chicago for a different journal, you'll need to change every in-text citation and reformat every reference list entry. Reference managers like Zotero or Mendeley make this easier by generating citations in any style. If you don't use a reference manager, budget several hours for the conversion — and run the final version through a proofreader to catch inconsistencies.

Q: What's the most common citation format in academia?

APA is the most widely used citation style globally, followed by Chicago and MLA. IEEE dominates engineering and computer science. Harvard variants are common in the UK, Australia, and parts of Asia. The "most common" style doesn't matter for your paper — what matters is the style your specific journal or institution requires. Check the author guidelines before formatting a single reference.

Q: Do I need to include DOIs for every source?

APA 7th edition requires DOIs for all sources that have them. MLA and Chicago don't require DOIs but increasingly recommend including them. IEEE doesn't include DOIs in standard reference formatting. In general, including DOIs is good practice regardless of style — they provide permanent, reliable links to sources. If a source has a DOI, include it unless your style guide explicitly says not to.

Q: How do I cite a source I found in another paper but haven't read myself?

This is called a secondary citation. In APA: (Original Author, Year, as cited in Author You Read, Year). In your reference list, include only the source you actually read. Most style guides discourage secondary citations — they want you to read the original. But when the original is truly inaccessible (out of print, in a language you don't read, behind an institutional paywall you can't access), a secondary citation is acceptable. Just don't make it a habit.