Annotated Bibliography: How to Write One in APA, MLA and Chicago

An annotated bibliography is a list of sources in which each citation is followed by a short paragraph, called an annotation, that tells the reader what the source says and why it matters to your topic. Most assignments expect each annotation to run roughly 100 to 200 words, or about three to six sentences, but your rubric overrides that range. The citation follows the style you are using, whether APA, MLA or Chicago, and the annotation sits directly under it.

This guide explains what goes into an annotation, shows a worked entry in each of the three major styles, and walks through writing one from scratch. If you still need to build the citations themselves, generate them first with our citation generator and paste each one above its annotation.

What is an annotated bibliography?

A plain bibliography only tells the reader where to find your sources. An annotated bibliography also records what you learned from each one. Instructors set it as a stand-alone assignment to check that you have read your sources critically, and researchers use it as a working file before they write a paper or thesis.

What an annotation does

A full annotation can do three jobs. You will not always need all three, so check what your assignment asks for.

Part	What it does
Summarize	States the source’s main argument, method or finding in your own words, in one to three sentences.
Evaluate	Judges the source: how credible the author is, how strong the evidence is, what bias or limits it has, and how it compares with your other sources.
Reflect	Explains how the source fits your project, for example which chapter it supports or which argument it challenges.

Annotated bibliography vs. reference list

The two are not the same list. APA explains that a reference list contains the works that support the claims in your paper, while a bibliography gives background or further reading and may include descriptive notes such as annotations. That is why a stand-alone annotated bibliography in APA follows the bibliography guidance in the Publication Manual (section 9.51) and not the reference-list rules. If your instructor wants an annotated list and a paper, you will usually submit them separately.

Annotated bibliography format: APA, MLA and Chicago

All three styles use the same recipe: a correctly formatted citation, then the annotation as a paragraph beneath it. What changes is the list title, the indent and the citation format. Each section below gives one worked entry, and the table after them puts the differences side by side.

Annotated bibliography example in APA 7

Format each source as a standard APA reference entry with a hanging indent. Start the annotation on a new line below it and indent the whole annotation 0.5 inch from the left margin. If an annotation runs to more than one paragraph, indent the first line of each later paragraph a further 0.5 inch. An annotated bibliography in APA starts from a normal journal reference, and our guide to citing journals shows how to build one. Our APA citation guide covers the full set of reference entries. Example:

Ryan, R. M., & Deci, E. L. (2000). Self-determination theory and the facilitation of intrinsic motivation, social development, and well-being. American Psychologist, 55(1), 68–78. https://doi.org/10.1037/0003-066X.55.1.68

Ryan and Deci set out self-determination theory, which argues that people are motivated when three needs are met: autonomy, competence and relatedness. The authors draw on decades of experimental work to separate intrinsic from extrinsic motivation. Because it is a theoretical overview and not a single study, it is most useful for framing a paper, and evidence for specific classroom or workplace settings has to come from other sources. This article provides the core framework for my second chapter.

Annotated bibliography example in MLA 9

Style each source as a works-cited entry. The MLA Style Center says a short phrase can follow the entry on the same line, but if you write full sentences, leave a line space after the entry and begin the annotation with a paragraph indent. Title the list “Annotated Bibliography” or “Annotated List of Works Cited”. Entries can be ordered by author, title, date or subject. An annotated bibliography in MLA treats a book like any works-cited entry, which our guide to citing books explains. See our MLA citation guide for the entry formats and the MLA Style Center’s guidance for the annotation rules. Example:

Ong, Walter J. Orality and Literacy: The Technologizing of the Word. Routledge, 2002.

Ong argues that writing does not merely record speech but restructures thought, contrasting the habits of mind in oral cultures with those of literate ones. His claims about memory and narrative are widely cited in media studies. The book is dense and written for scholars, yet its central contrast gives me a clear lens for the unit on digital reading.

Annotated bibliography example in Chicago style

Chicago bibliography entries use a hanging indent with the author’s name inverted. The Chicago citation guide does not prescribe one annotation layout, so use the layout your instructor gives you. The common convention is to place the annotation as a brief paragraph indented beneath the entry, written in full sentences or in fragments, and to keep one choice throughout. The details of the entries are in our Chicago citation guide, and the official notes and bibliography guide shows the entry formats. Example:

Carr, Nicholas. The Shallows: What the Internet Is Doing to Our Brains. New York: W. W. Norton, 2010.

Carr argues that sustained use of the internet weakens deep reading and concentration. The book blends neuroscience, media history and personal observation. Its claims are broad and sometimes rest on popular summaries of research, so I treat it as a provocative argument and not as proof.

APA vs. MLA vs. Chicago at a glance

Feature	APA 7	MLA 9	Chicago
List title	Annotated Bibliography	Annotated Bibliography or Annotated List of Works Cited	Annotated Bibliography
Entry	Reference entry, hanging indent, date after author	Works-cited entry, no date after author	Bibliography entry, publication city often included
Annotation position	New line, whole block indented 0.5 inch	After a line space with a paragraph indent, or a short phrase on the same line	Paragraph beneath the entry, as your instructor directs
Order	Alphabetical by author	Author, title, date or subject	Alphabetical by author

How to write an annotated bibliography

Work through the list one source at a time. Doing the citation first keeps the format correct and leaves you free to concentrate on the annotation.

1. Define the topic and the scope. Write your research question in one sentence so you can judge whether each source belongs.
2. Find and select sources. Use library databases and your course reading list. Prefer peer-reviewed articles, scholarly books and primary documents, and drop anything you cannot attribute to an author or publisher.
3. Build the citation. Format it in the required style and put it in order.
4. Read the source closely. Read the introduction and conclusion first, then the methods and results, and note the main claim, the evidence used and any limits.
5. Write the summary. One to three sentences on the argument or finding, in your own words. If you struggle to avoid the source’s phrasing, see paraphrasing vs. summarizing.
6. Add the evaluation and the reflection. Comment on credibility and bias, then say how the source helps your project.
7. Check length and consistency. Trim to the word range in your rubric, keep one tense and voice, and compare every entry’s layout against the style guide.

How long should an annotation be?

Instructors rarely set a hard rule, but the usual range is 100 to 200 words per source. The three sample annotations above run 79 words (APA), 60 words (MLA) and 46 words (Chicago), which shows that two or three well-chosen sentences can be enough when the assignment asks for a short summary. The table links length to content so you can decide how much to write.

Length	What fits
One short phrase	A descriptive tag, as MLA allows. Use it only if your instructor says so.
3 to 4 sentences (about 60 to 100 words)	Summary plus one evaluative remark.
5 to 6 sentences (about 100 to 200 words)	Summary, evaluation and reflection. The standard university annotation.
More than one paragraph	Only when the assignment asks for it. APA then indents the first line of each later paragraph.

Choosing sources worth annotating

The research strategy comes before the writing, because a weak source produces a weak annotation. Run each candidate through the checks below before you spend time on it.

Check	What to look for
Where to search	Your library’s databases and catalogue first, then the reference lists of the best articles you find.
Author and publisher	A named author with relevant expertise and a scholarly publisher or journal.
Date	Recent enough for your field, or a classic that your topic still depends on.
Evidence	Sources, data or a stated method, so that you have something to evaluate.
Fit	You can say in one sentence how the source helps your research question.

Descriptive vs. evaluative annotations

Some instructors want only a summary and others want a judgment. The table shows the difference using the Ryan and Deci article from the APA example.

Type	What it contains	Example sentence
Descriptive (informative)	What the source says. No judgment.	The article presents self-determination theory and its three basic psychological needs.
Evaluative (critical)	What the source says, plus how well it says it.	The article is a theoretical overview, so its claims about classroom settings need support from empirical studies.
Combined	Summary, evaluation and reflection together. The usual choice for university work.	The article gives the framework for my second chapter, although it needs empirical sources alongside it.

Common mistakes in annotations

The MLA Style Center warns that annotations should not rehash minor details, cite evidence, quote the author or recount the steps of an argument. The table adds other slips that lose marks, with a quick way to spot each.

Mistake	How to spot it
Copying the abstract	Your sentences match the abstract’s wording. Rewrite the point from memory without looking.
Summary only	No sentence judges the source or links it to your project. Add one evaluative sentence.
Retelling the argument step by step	The annotation walks through sections in order. Give the main claim, then stop.
Over-quoting	Quotation marks appear in the annotation. Paraphrase instead.
Wrong indent or spacing	The annotation sits flush with the citation. Compare against the style table above.
Unequal lengths	One annotation is 40 words and another is 300. Aim for a consistent range.

Frequently asked questions about annotated bibliographies

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