A thorough comparison of the three dominant citation styles used in academic writing. Understand the rules, see formatted examples side by side, and learn which style fits your discipline.
A citation is a reference to a source. More precisely, a citation is an abbreviated alphanumeric expression embedded in the body of an intellectual work that denotes an entry in the bibliographic references section of the work for the purpose of acknowledging the relevance of the works of others to the topic of discussion at the spot where the citation appears. Generally the combination of both the in-body citation and the bibliographic entry constitutes what is commonly thought of as a citation.
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Proper citation is the backbone of scholarly communication. It allows readers to trace the origins of ideas, verify claims, and build upon existing research. Choosing the wrong citation format for a class assignment or journal submission can result in grade deductions or manuscript rejection. More importantly, inconsistent citations make your work look unprofessional and undermine reader trust.
The three most widely used citation styles in English-language academia are APA (American Psychological Association), MLA (Modern Language Association), and Chicago/Turabian. Each was designed for a specific set of disciplines, and each has distinct rules for formatting in-text citations, reference lists, and document layout. This guide walks through every major rule so you can pick the right format and apply it correctly.
Throughout this guide, you can use the free APA Citation Generator and Citation Generator tools to format your references automatically once you know which style you need.
| Feature | APA 7th Edition | MLA 9th Edition | Chicago 17th Edition |
|---|---|---|---|
| Governing body | American Psychological Association | Modern Language Association | University of Chicago Press |
| Primary disciplines | Psychology, education, social sciences, nursing | Literature, languages, cultural studies, arts | History, publishing, some humanities and sciences |
| In-text citation style | Author-date: (Smith, 2024) | Author-page: (Smith 45) | Notes-Bibliography (footnotes) or Author-Date |
| End-of-paper list | References | Works Cited | Bibliography or References |
| Title page required | Yes (professional and student formats differ) | No (header on first page instead) | Optional (often yes for formal papers) |
| Running head | Optional for students, required for professionals | Last name + page number in header | Not required; page numbers only |
| Current edition year | 2019 | 2021 | 2017 |
APA is the default citation style for most social science, education, and nursing programs. If your professor says "use APA," they almost certainly mean the 7th edition (published in 2019). Key characteristics include emphasis on the date of publication (because recency matters in sciences) and a structured, heading-based paper format with specific levels of headings.
APA uses an author-date parenthetical system. The basic format places the author's last name and the year of publication inside parentheses. When quoting directly, include a page number after a comma.
Parenthetical citation: Research confirms the link between sleep and memory consolidation (Walker, 2017).
Narrative citation: Walker (2017) confirmed the link between sleep and memory consolidation.
Direct quote: "Sleep is the single most effective thing we can do to reset our brain" (Walker, 2017, p. 7).
For two authors, join with an ampersand in parenthetical citations or "and" in narrative citations. For three or more authors, use the first author's last name followed by "et al." from the very first citation.
The reference list appears on its own page titled "References" (centered). Each entry uses a hanging indent (first line flush left, subsequent lines indented 0.5 inches). Entries are alphabetized by the first author's last name.
Book format:
Author, A. A. (Year). Title of work: Capital letter also for subtitle.
Publisher. https://doi.org/xxxxx
Journal article format:
Author, A. A., Author, B. B., & Author, C. C. (Year). Title of
article. Title of Periodical, volume(issue), page-page.
https://doi.org/xxxxx
Website format:
Author, A. A. (Year, Month Day). Title of page. Site Name.
https://url.com/page
APA papers use 1-inch margins on all sides, double-spacing throughout, and 12-point Times New Roman, Calibri 11pt, or Arial 11pt font. The 7th edition introduced a simpler student paper format that does not require a running head. Professional papers retain the running head: a shortened version of the title (up to 50 characters) in all caps at the top left of every page.
APA uses five levels of headings. Level 1 headings are centered and title case. Level 2 headings are flush left and title case. Level 3 headings are flush left, italic, and title case. Level 4 headings are indented, title case, and end with a period. Level 5 headings are indented, italic, title case, and end with a period.
MLA is the standard in literature, language studies, cultural studies, and many arts programs. The 9th edition (2021) simplified many rules from earlier editions, particularly for online sources. MLA emphasizes the location of information within a source (page numbers) rather than publication date, because humanities scholarship does not become outdated in the same way that scientific research can.
MLA uses an author-page parenthetical system. No comma separates the author's name from the page number, and no "p." abbreviation precedes the number.
Parenthetical citation: Language shapes thought in measurable ways (Boroditsky 65).
Narrative citation: Boroditsky argues that language shapes thought in measurable ways (65).
No page number: When citing an entire work or a web source without pages, use the author's name alone (Boroditsky).
For two authors, include both with "and" between them. For three or more authors, use the first author followed by "et al." at every instance.
MLA 9th edition uses a container model. Every source has core elements: Author, Title of source, Title of container, Other contributors, Version, Number, Publisher, Publication date, and Location. You fill in what applies and skip what does not.
Book format:
Author Last, First. Title of Book. Publisher, Year.
Journal article format:
Author Last, First. "Title of Article." Journal Name, vol. #,
no. #, Year, pp. #-#.
Website format:
Author Last, First. "Title of Page." Website Name, Day Month Year,
URL.
MLA papers use 1-inch margins, double-spacing, and a legible 12-point font (typically Times New Roman). There is no title page; instead, the first page includes a header block in the upper left corner with the student's name, the instructor's name, the course, and the date. The title is centered on the next line, in regular font. A running header with the student's last name and page number appears in the upper right corner of every page.
MLA does not use a formal heading system like APA. Section headings are acceptable but not required, and formatting is left to the writer's discretion. The MLA Handbook recommends making headings consistent and descriptive.
Chicago style is dominant in history departments and widely used in publishing, fine arts, and some social sciences. Its defining feature is flexibility: it offers two completely separate citation systems within the same manual. The Notes-Bibliography (NB) system uses footnotes or endnotes paired with a bibliography, while the Author-Date (AD) system uses parenthetical citations paired with a reference list. Most history professors require the NB system.
In the NB system, a superscript number follows the cited text. The corresponding footnote at the bottom of the page provides full source information the first time a source is cited. Subsequent citations of the same source use a shortened form.
First footnote for a book:
1. Author First Last, Title of Book (Place: Publisher, Year), page.
Shortened footnote:
2. Last, Short Title, page.
The bibliography at the end inverts the first author's name (Last, First) and uses periods instead of commas between elements. Entries are alphabetized by last name and use hanging indents.
Bibliography entry for a book:
Last, First. Title of Book. Place: Publisher, Year.
The AD system works similarly to APA. In-text citations take the form (Author Year, page), and the reference list at the end includes full details. This system is less common in humanities but appears in some social science and science disciplines that prefer Chicago over APA.
(Smith 2024, 112)
Chicago style uses 1-inch margins, double-spacing for the body text (footnotes can be single-spaced), and a 12-point serif font. A title page is generally expected, with the title centered about one-third of the way down the page, followed by the author's name and course information lower on the page. Page numbers appear in the header, starting from the second page.
| Style | Reference/Bibliography Entry |
|---|---|
| APA | Walker, M. (2017). Why we sleep: Unlocking the power of sleep and dreams. Scribner. |
| MLA | Walker, Matthew. Why We Sleep: Unlocking the Power of Sleep and Dreams. Scribner, 2017. |
| Chicago NB | Walker, Matthew. Why We Sleep: Unlocking the Power of Sleep and Dreams. New York: Scribner, 2017. |
| Style | Reference/Bibliography Entry |
|---|---|
| APA | Smith, J. A., Lee, K., & Patel, R. (2023). The role of citation in knowledge transfer. Academic Publishing Quarterly, 45(2), 112-130. https://doi.org/10.xxxx |
| MLA | Smith, John A., et al. "The Role of Citation in Knowledge Transfer." Academic Publishing Quarterly, vol. 45, no. 2, 2023, pp. 112-130. |
| Chicago NB | Smith, John A., Kira Lee, and Raj Patel. "The Role of Citation in Knowledge Transfer." Academic Publishing Quarterly 45, no. 2 (2023): 112-130. |
| Style | Reference/Bibliography Entry |
|---|---|
| APA | National Institutes of Health. (2025, January 15). Sleep deprivation and deficiency. https://www.nhlbi.nih.gov/health/sleep-deprivation |
| MLA | "Sleep Deprivation and Deficiency." National Institutes of Health, 15 Jan. 2025, www.nhlbi.nih.gov/health/sleep-deprivation. |
| Chicago NB | National Institutes of Health. "Sleep Deprivation and Deficiency." Accessed March 20, 2026. https://www.nhlbi.nih.gov/health/sleep-deprivation. |
One of the most frequent errors is blending rules from different citation styles. A paper that uses APA in-text citations but MLA formatting for the reference list will confuse readers and lose marks. Stick to one style throughout. If you are unsure which style your professor requires, ask before you start writing.
APA uses initials for given names (Walker, M.), MLA uses the full first name (Walker, Matthew), and Chicago NB also uses the full first name (Walker, Matthew). Switching between these formats within a single reference list signals carelessness.
APA 7th edition requires DOIs formatted as URLs (https://doi.org/10.xxxx). Earlier practice used "doi:" as a label, but this is now outdated. MLA generally omits DOIs in favor of permalinks or stable URLs. Chicago includes DOIs when available. Always check that your links resolve correctly before submitting.
APA uses sentence case for article and book titles in the reference list (only the first word and proper nouns capitalized), but title case for journal names. MLA uses title case for everything. Chicago uses title case for book and article titles in the bibliography. Getting capitalization wrong is a giveaway that you formatted manually without checking the rules.
Style guides update periodically. If your professor says "use APA" without specifying an edition, default to the most recent one (7th). The same applies to MLA (9th) and Chicago (17th). Rules from older editions may conflict with current guidelines.
If you are writing for a specific journal, always check the journal's submission guidelines first. Most journals specify a required citation style in their author instructions. For coursework, your professor or department will typically specify the style. Here is a general guideline when no style is specified:
When in doubt, APA is the safest general-purpose choice because of its wide adoption across disciplines. However, never assume; confirm with your instructor or publisher.
When you read a quote in one source that was originally published in another, you are dealing with a secondary source. APA handles this with "as cited in": (Original Author, Year, as cited in Reading Author, Year). MLA uses "qtd. in": (qtd. in Reading Author 45). Chicago NB includes the original source information in the footnote and references the source you actually read. Always try to find and cite the original source when possible.
APA 7th edition added specific formats for tweets, Instagram posts, TikTok videos, and similar content. The general format includes the author's name (with handle), the date, the first 20 words of the content as the title, the platform name in brackets, and the URL. MLA treats social media posts like web content with the platform as the container. Chicago suggests treating social media as a footnote-only citation in most cases.
In APA, order reference entries by the same author chronologically (earliest first). Use "a," "b," "c" suffixes for works published in the same year (2024a, 2024b). In MLA, alphabetize by title and use three hyphens followed by a period (---.) to replace the author's name after the first entry. In Chicago NB, use the same three-em-dash convention in the bibliography.
APA lists the translator after the title: Author, A. A. (Year). Title (B. B. Translator, Trans.). Publisher. (Original work published Year). MLA includes the translator as another contributor: Author Last, First. Title. Translated by First Last, Publisher, Year. Chicago NB places the translator after the title: Author First Last, Title, trans. First Last (Place: Publisher, Year).
When citing a chapter from an edited book, include both the chapter author and the editor. APA format: Chapter Author, A. A. (Year). Title of chapter. In E. E. Editor (Ed.), Title of book (pp. xx-xx). Publisher. MLA format: Chapter Author Last, First. "Title of Chapter." Title of Book, edited by First Last, Publisher, Year, pp. xx-xx. In Chicago NB, the footnote begins with the chapter author and title, followed by "in Title of Book, ed. First Last."
Government reports in APA use the agency as the author: U.S. Department of Education. (Year). Title of report (Publication No. xxx). URL. MLA follows a similar pattern with the agency as author. Legal citations follow entirely different conventions (Bluebook for U.S. law); consult a legal citation guide for court cases, statutes, and regulations.
Manual citation formatting is tedious and error-prone. Reference management tools can save significant time, especially for longer research papers with dozens of sources.
Zotero is a free, open-source reference manager that integrates with Word and Google Docs. It can automatically detect and import citation data from web pages, library databases, and PDFs. Mendeley offers similar features with built-in PDF annotation. EndNote is a commercial option popular in sciences and medicine.
For quick one-off formatting, free online generators are often the fastest option. The Zovo APA Citation Generator handles APA 7th edition formatting for books, journals, websites, and more. The general-purpose Citation Generator supports multiple styles and source types.
Open APA Citation Generator Open Citation GeneratorWhile citation formatting is primarily an academic concern, developers frequently discuss BibTeX, CSL (Citation Style Language), and automated citation parsing. Here are relevant community threads:
Search YouTube for "APA vs MLA vs Chicago citation tutorial" to find walkthroughs that demonstrate side-by-side formatting for each style. The Purdue OWL channel and Scribbr channel both offer updated, comprehensive video guides covering the latest editions.
| Browser | Citation Generator | APA Generator | Copy to Clipboard |
|---|---|---|---|
| Chrome 90+ | Full support | Full support | Full support |
| Firefox 88+ | Full support | Full support | Full support |
| Safari 14+ | Full support | Full support | Full support |
| Edge 90+ | Full support | Full support | Full support |
| Mobile Chrome | Full support | Full support | Full support |
| Mobile Safari | Full support | Full support | Full support |
Does my high school accept MLA format? Most U.S. high schools default to MLA for English classes and APA for science courses. Always check your specific assignment instructions.
Can I use footnotes in APA? APA allows footnotes for supplementary content or copyright attribution, but not for source citations. Only Chicago NB uses footnotes as its primary citation method.
What about Turabian style? Turabian is a simplified version of Chicago style designed for students. If your professor assigns Turabian, you are using Chicago rules with minor modifications (such as a different title page format). Turabian's A Manual for Writers is based directly on the Chicago Manual of Style.
Do I need to cite common knowledge? No. Facts that are widely known and verifiable in multiple general reference sources (such as "water boils at 100 degrees Celsius at sea level") do not need citations. However, when in doubt, cite it. Over-citation is always safer than under-citation in academic work.
How do I cite a source I found in a database like JSTOR? Cite the source itself (the journal article, book chapter, etc.), not the database. APA 7th edition specifies that database names should not be included in references unless the work is only available through that database. Use the DOI when available.
Is it plagiarism if I cite incorrectly? Incorrect citations are not plagiarism in the intentional sense, but they can still result in academic integrity concerns if a reader cannot locate your source. Sloppy citations can be interpreted as an attempt to obscure the origin of borrowed ideas. Take citation formatting seriously.
How many sources should a research paper have? There is no universal rule, but a general guideline is one to two sources per page of body text for undergraduate papers. Graduate-level research papers and literature reviews typically require significantly more. Quality matters more than quantity: five well-chosen, peer-reviewed sources are more valuable than twenty superficial web pages.
An annotated bibliography is a list of citations followed by a brief descriptive or evaluative paragraph (the annotation). Annotations typically range from 100 to 300 words and serve a different purpose than a standard reference list. While a reference list simply identifies your sources, an annotated bibliography evaluates each source's credibility, relevance, and quality.
The annotation usually addresses three questions: What is the source about? How was the research conducted? How is this source useful to your research? Some instructors also require a reflection on how the source compares to others in the bibliography.
Formatting follows the same citation style rules as your paper. The citation appears first in the correct format (APA, MLA, or Chicago), followed by the annotation indented below. In APA, the annotation is on a new line with a standard paragraph indent. In MLA, the annotation begins on the line after the citation and is indented to match the hanging indent.
Annotated bibliographies are commonly assigned in graduate courses and as preliminary steps in research projects. They force researchers to critically evaluate each source rather than collecting citations passively. This process frequently reveals gaps in the literature and helps refine research questions before the actual writing begins.
DOIs have become central to modern citation practice. A DOI is a permanent, unique identifier assigned to a digital document, typically a journal article, book chapter, or dataset. Unlike URLs, which can break when publishers restructure their websites, DOIs are managed by the International DOI Foundation and are designed to resolve permanently.
In APA 7th edition, DOIs are formatted as full URLs: https://doi.org/10.1234/example. The "doi:" prefix used in earlier editions is no longer correct. If a source has a DOI, always use it instead of a database URL. Crossref (crossref.org) maintains the largest DOI registration database and provides a free lookup tool for finding DOIs.
For sources without DOIs, APA recommends using the direct URL of the work. MLA similarly prefers stable URLs or permalinks over database-generated links. When using URLs, remove any tracking parameters (the characters after a question mark in many URLs) to keep citations clean and functional.
Some publishers assign alternative persistent identifiers. PubMed IDs (PMIDs) are common in medical literature, and arXiv identifiers are standard in physics and mathematics. While these are useful for locating sources, the DOI remains the preferred identifier in all three major citation styles when available.
Citation is not merely a formatting exercise. It is a fundamental component of academic integrity. Proper citation acknowledges intellectual debts, allows readers to verify your claims, positions your work within existing scholarship, and protects you from accusations of plagiarism.
Plagiarism takes several forms beyond simply copying text. Paraphrasing without attribution (restating someone else's idea in your own words without citing the source) is plagiarism. Self-plagiarism (reusing your own previously published work without disclosure) is considered a form of academic dishonesty in many institutions. Mosaic plagiarism (weaving together phrases from multiple sources without quotation marks or citations) is especially difficult to detect but equally problematic.
Most universities use plagiarism detection software (Turnitin, iThenticate, Copyscape) that compares submitted papers against databases of published work, previous submissions, and web content. These tools generate similarity reports that highlight matching text. However, high similarity scores do not automatically indicate plagiarism; properly quoted and cited passages will match source text by definition. The concern is matching text without corresponding citations.
When in doubt about whether to cite, always err on the side of inclusion. The worst outcome of over-citation is a slightly longer reference list. The worst outcome of under-citation is an integrity violation that can result in course failure, academic probation, or dismissal.
For researchers managing dozens or hundreds of sources, manual citation formatting is not practical. Reference management software automates the process by storing source metadata, generating formatted citations, and inserting them into documents.
| Feature | Zotero | Mendeley | EndNote |
|---|---|---|---|
| Price | Free (300MB cloud storage) | Free (2GB storage) | $274 (one-time) or $157/year |
| Word processor integration | Word, Google Docs, LibreOffice | Word only | Word only |
| Browser extension | Yes (all major browsers) | Yes (Chrome, Firefox) | Yes (limited) |
| PDF management | Basic | Advanced (annotation, highlighting) | Advanced |
| Collaboration | Group libraries (free) | Private groups (limited free) | Share libraries (paid) |
| Citation styles | 10,000+ CSL styles | 7,000+ CSL styles | 6,000+ styles |
| Open source | Yes | No | No |
For most students and independent researchers, Zotero is the recommended choice. It is free, open source, works with every major word processor, and has the largest library of citation styles. Its browser extension can automatically capture citation data from library catalogs, publisher websites, Amazon, and many other sources with a single click.
Mendeley is owned by Elsevier and offers stronger PDF annotation features, which makes it popular among researchers who read many papers on screen. However, its acquisition by a major publisher has raised concerns about data privacy and vendor lock-in among some researchers.
EndNote is the most established commercial option and remains standard in many medical and scientific research groups. Its price is justified for researchers who need its advanced features, such as manuscript matching and full-text PDF retrieval.
Update History
March 20, 2026 - Initial publication. Covers APA 7th edition, MLA 9th edition, and Chicago 17th edition with side-by-side examples, annotated bibliography guidance, DOI practices, citation ethics, and reference management tools.
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