Citation styles ensure academic integrity by standardizing how sources are credited. The four most widely used styles — APA, MLA, Chicago, and IEEE — each format citations differently. This guide shows side-by-side examples for journal articles, books, and websites in all four styles.
How to Choose and Use Citation Styles
Citation styles exist for practical reasons: they create predictable formats that make it easy for readers to locate the sources you cited. Each discipline developed its own style based on what information matters most in that field. Scientists and social scientists need publication dates prominently displayed (hence APA's author-date format). Humanities scholars often prefer reading flow with footnotes (Chicago notes-bibliography).
APA vs MLA: The Most Common Confusion
APA uses the author-date citation format in-text: (Smith, 2023) or (Smith, 2023, p. 45) for direct quotes. MLA uses author-page number: (Smith 45). In the bibliography/works cited, APA puts the year immediately after the author name; MLA puts it near the end of the entry. When in doubt in academic settings, check your course syllabus or ask your instructor — they'll specify which style to use.
Using Citation Managers
For research papers with more than 10 sources, a citation manager (Zotero, Mendeley, or EndNote) is more efficient than formatting manually. These tools store your source database and automatically generate formatted citations and bibliographies in any style. Zotero is free and open-source with browser integration for capturing sources from web pages and databases. Always verify auto-generated citations — citation managers occasionally format edge cases incorrectly.
FAQ
Is this citation guide free?
Yes, completely free with no signup required.
Which citation style should I use?
Citation style is usually determined by your field or instructor. APA (American Psychological Association) is standard for social sciences, psychology, education, and business. MLA (Modern Language Association) is standard for humanities, literature, and arts. Chicago is used for history and some humanities. IEEE is standard for engineering, computer science, and technical fields.
What is the difference between APA 6th and 7th edition?
APA 7th edition (2020) has several changes from 6th: running heads are only required for manuscripts submitted for publication (not student papers), in-text citations for works with 3+ authors now use 'et al.' from the first citation (was 6+ in 6th), DOIs are formatted as hyperlinks (https://doi.org/...), and the title page format differs for student vs professional papers.
What is DOI and when do I need it in citations?
DOI stands for Digital Object Identifier — a permanent URL for academic articles and publications. Include DOIs in citations whenever they are available. In APA 7th, format as: https://doi.org/xxxxxx. In MLA 9th, include as a URL if no other access method is listed. In Chicago, DOIs appear at the end of citations when available. Always prefer DOI over URL — DOIs are permanent; URLs change.
How do I cite a website with no author or date?
APA: Use the organization name as author; use 'n.d.' for no date. Example: Organization Name. (n.d.). Page title. Website Name. URL. MLA: Start with the article/page title in quotes. Include the website name, publication date if available or 'n.d.', and URL. Chicago: Include the author or organization, title, site name, access date, and URL in footnote/bibliography format.
What is the difference between footnote and author-date citation?
Author-date citations appear in-text (Smith, 2023) and are used in APA, MLA, and IEEE styles. Footnote/endnote citations appear as numbered superscripts in the text with full citations at the bottom of the page or end of the document — used in Chicago Notes-Bibliography style (common in humanities). Chicago also offers an author-date variant used in social sciences.