How to Write an Annotated Bibliography
Updated November 6, 2026
To write an annotated bibliography, list your sources in the citation style your professor wants, then add a short paragraph under each one. That paragraph is called an annotation. It sums up the source and often says how useful it is. Cornell’s library guide says annotations usually run about 150 words, but your assignment has the final say.
What is an annotated bibliography?
A bibliography is a list of sources. An annotated bibliography adds a note to each one.
An annotation isn’t the same as an abstract. An abstract only describes a source. An annotation describes it and also judges it.
Types of annotations
Purdue OWL says annotations can do three jobs. Your assignment may ask for one job or all of them.
| Job | What you write | Question it answers |
|---|---|---|
| Summarize | The main argument and topics | What does this source say? |
| Assess | How reliable and useful it is | How good is this source? |
| Reflect | How it fits your research | How will I use this source? |
How to write one in 6 steps
1. Check the assignment
Find out which citation style to use, how many sources you need, and how long each annotation should be. Check which of the three jobs your professor wants.
2. Choose and read your sources
Pick sources that speak to your topic, and read them before you write. Our guide on how to tell if a source is credible can help you weed out weak ones.
3. Write the citation
Put the full citation first. The free citation generator from Sourcefox can give you a draft. Then compare it with the source and with our MLA 9 examples or Chicago examples.
4. Summarize the main point
Write two or three sentences in your own words. Say what the author argues or finds. Stick to the big picture. The MLA advises leaving out minor details and quotes from the author.
5. Judge the source
Say what makes it strong or weak. Look at the author’s background, the evidence, and the size of the study. If another source disagrees, say so.
6. Say how you’ll use it
End with a sentence on how this source fits your paper. Maybe it gives you background, or maybe it supports one of your points. If your assignment only asks for a summary, skip this part.
Annotated bibliography example in MLA 9
Both sources below are real. We checked the citation details against Crossref.
Mueller, Pam A., and Daniel M. Oppenheimer. “The Pen Is Mightier than the Keyboard: Advantages of Longhand over Laptop Note Taking.” Psychological Science, vol. 25, no. 6, 2014, pp. 1159-68, https://doi.org/10.1177/0956797614524581.
Mueller and Oppenheimer ran three studies that compared students who took notes by hand with students who used laptops. Laptop users did worse on conceptual questions. The authors argue that laptop users copy lectures word for word and don’t put ideas in their own words. The paper is useful because it offers a reason for the result. Its main limit is that later work questions the finding. I’ll use it to introduce the debate in my section on study habits.
That one annotation does all three jobs. It summarizes the study, assesses it, and says how the writer will use it.
Annotated bibliography example in Chicago 17
Morehead, Kayla, John Dunlosky, and Katherine A. Rawson. “How Much Mightier Is the Pen than the Keyboard for Note-Taking? A Replication and Extension of Mueller and Oppenheimer (2014).” Educational Psychology Review 31, no. 3 (2019): 753–80. https://doi.org/10.1007/s10648-019-09468-2.
Morehead, Dunlosky, and Rawson repeated Mueller and Oppenheimer’s study and extended it. They didn’t find as clear an advantage for handwritten notes as the original study did. This is a strong source for my paper because it tests a famous claim directly. I’ll use it to show that the original finding didn’t fully hold up.
Notice how the second annotation talks to the first one. That’s the kind of thinking professors want to see.
How to format it
Keep your list in alphabetical order by author unless your professor says otherwise. Each citation gets a hanging indent, so only the first line sits at the left margin. Format each citation the same way you would in a normal source list.
| Style | Annotation indent |
|---|---|
| MLA 9 | 1 inch |
| APA 7 | 0.5 inch |
| Chicago 17 | 0.5 inch |
The indents come from Purdue OWL’s samples. In MLA, title the list Annotated Bibliography or Annotated List of Works Cited. Professors often have their own layout rules, so check your assignment first.
Sentence starters that help
Stuck on how to begin? Try these:
- “The author argues that…”
- “This study found that…”
- “This source is useful because…”
- “One limit of this source is…”
- “I plan to use this source to…”
Common mistakes to avoid
- Copying the abstract. That’s not your work, and it won’t show you read the source.
- Writing only a summary when your professor asked for an evaluation.
- Listing a source you haven’t opened.
- Going over the word limit. A free word counter makes this easy to check.
Common questions
How long should an annotated bibliography be?
It depends on your assignment and your number of sources. Purdue OWL says annotations can run from a couple of sentences to a couple of pages. About 150 words each is a common length.
Can I use “I” in an annotated bibliography?
Often, yes, in the part where you explain how you’ll use the source. Summaries usually read better without it. Ask your professor if you’re not sure.
Do I have to read the whole source?
Read enough to judge it honestly. For a journal article, that usually means the whole paper. For a long book, your professor may be fine with the introduction, the conclusion, and the chapters you plan to use.