How do I know if a source is reliable?

Check who produced it and why, whether the claims are backed by evidence, how current it is and whether other reliable sources agree. Reading what others say about the source, called lateral reading, is often faster than studying the page itself.

What is the CRAAP test?

A checklist that asks about a source's Currency, Relevance, Authority, Accuracy and Purpose. It is a useful starting point, but it works best alongside lateral reading and checking the evidence.

Is a peer-reviewed article always reliable?

Not always. Peer review is a useful filter, but weak studies, errors and even retracted papers exist. Read the method and limitations, and check whether the article has been corrected or retracted.

Many instructors do not accept it as a citation, but it can help you find background and the original sources, which you can then read and cite.

How do I judge a source with a clear opinion?

All sources have a perspective. Opinionated sources can be valuable as evidence of a viewpoint. What matters is that you identify the bias, check its claims against other sources and describe it accurately.

Evaluating Sources: How to Judge What You Read

Finding sources is only half of research. The other half is deciding which ones to trust, which to use with care and which to leave alone. Students are often told to "use credible sources" without being shown what credibility looks like in practice, and the internet makes the job harder: polished websites can be wrong, and plain ones can be excellent.

This guide gives you a practical method for evaluating sources, from quick checks to deeper questions, and applies it to journals, websites, news, reports and AI-generated text.

Why evaluation matters

Your argument is only as strong as the evidence behind it. A weak source can undermine a good paper, and an uncritical use of sources is one of the most common reasons for lower marks. Evaluation also protects you from error: the habit of asking where a claim came from is useful long after college.

A quick test: CRAAP

The CRAAP test, developed by librarians, is a handy checklist.

Letter	Question	What to look for
Currency	How recent is it?	Publication or update date, and whether newer research exists
Relevance	Does it fit my question?	Topic, audience and level of detail
Authority	Who is responsible?	Author credentials, publisher, affiliation
Accuracy	Is it supported?	Evidence, citations, method, consistency with other sources
Purpose	Why does it exist?	Inform, persuade, sell or entertain, and any bias

The test is a good start, but it has limits. Websites can look authoritative and accurate while being misleading, so go beyond the page itself.

Read laterally

Researchers who study how experts check information found that fact-checkers do not stay on the page. They open new tabs and check what others say about the source. This is called lateral reading. Try it when you meet an unfamiliar site or organization:

Leave the page. Search the name of the organization or author.
Look at independent sources, such as encyclopedias, news coverage and academic profiles.
Find out who funds it and what it wants.
Check the claim elsewhere. Does it appear in reliable sources?
Return to the original source with a better sense of how far to trust it.

A few minutes of lateral reading often tells you more than a long study of the site itself.

Questions to ask

Authority

Who wrote it? Do they have relevant training or experience?
What organization published it, and what is its reputation?
Is the author an expert in this specific area?
Is there contact information and a clear way to check credentials?

Evidence

What evidence supports the claims? Data, studies, documents?
Are sources cited, and can you check them?
If it is a study, is the method described, and does it fit the question?
Is the sample large and appropriate?
Do the conclusions follow from the results, or go beyond them?

Purpose and bias

Is the aim to inform, persuade, sell or entertain?
Who benefits if you believe it?
Is the language balanced or loaded?
Are other viewpoints acknowledged?
Are there conflicts of interest, such as funding from a party with a stake?

Currency

When was it published or last updated?
Does the topic change quickly, such as technology or medicine?
Has newer research replaced it?

Fit

Does it answer my question, or is it only loosely related?
Is it at the right level for my assignment?

Different kinds of sources

Journal articles

Peer review helps, but still check the journal's reputation, the method and the limitations. Be wary of journals that publish quickly for a fee with little review. Look at the article type: research articles, reviews and commentaries carry different weight. Our guide to finding peer-reviewed articles covers how to check a journal.

Books

Academic presses use review processes, while self-published or popular books vary. Check the author's credentials, the publisher and whether the book cites sources.

Websites

Domains such as .edu or .gov are not guarantees. Check the organization, the author, the date and the sources. Look for an About page, and use lateral reading.

News and magazines

Reputable outlets have editorial standards, but reporting is secondary. For research claims, find the original study and read it. Distinguish news reports from opinion pieces.

Reports from organizations

Government agencies, international bodies and professional associations often produce valuable reports. Check the methods, the funding and whether the organization has an agenda.

Social media and videos

Treat them as evidence of what people say, not of what is true. Verify claims in reliable sources, and check who posted them.

AI-generated text

AI tools can produce fluent text that is wrong, including invented sources. Never treat an AI answer as a source of facts. Find and read the real sources, and check any reference it suggests. Our guide to citing AI tools explains how to handle it if your course allows use.

Primary and secondary sources

A primary source is original evidence: a study report, a document, a dataset, an interview or a speech. A secondary source interprets or summarizes primary sources, such as a review article or textbook. Use primary sources for key claims whenever you can, and secondary sources for background and interpretation. If you rely on a secondary source's description of a study, you inherit its errors.

Spotting weak studies

When you read research, check for signs of weakness.

Very small or unrepresentative samples.
No comparison group where one is needed.
Self-selected participants.
Results that go beyond the data.
Correlation described as causation.
Missing method details.
Conflicts of interest not disclosed.
Surprising claims from a single study.

One study rarely settles a question. Look for replication and for agreement among several well-designed studies.

Retractions and corrections

Journals sometimes retract papers because of errors or misconduct, and publish corrections. Before relying on a key article, check the journal page and a retraction database for notices. Citing a retracted paper as valid evidence is a serious error.

Metrics are not quality

Citation counts and journal impact factors indicate attention, not truth. A highly cited paper may be influential because it is controversial or wrong. Use metrics as a clue about visibility, not as proof of quality.

Using a source with a clear bias

Biased sources are not useless. A think tank report, a company white paper or an advocacy group statement can be good evidence of a position. The key is to be transparent: name the source's perspective, check its claims against independent evidence and avoid presenting it as neutral.

Deciding what to cite

Use this quick decision guide.

Is the source relevant to my question?
Is the author or organization credible for this topic?
Is the evidence clear and checkable?
Is it current enough?
Does independent evidence support its main claims?
Is the bias understood and acknowledged?

If you can answer yes to most, cite it. If not, look for a better source or use it with a clear caution.

Common mistakes

Trusting a source because it looks professional.
Using the first search results without checking.
Treating "peer reviewed" as proof.
Relying on secondary summaries of key studies.
Ignoring dates in fast-moving fields.
Assuming .org or .edu means reliable.
Using AI text as a source.
Citing without reading.

A quick checklist

Who made this, and why?
What is the evidence, and can I check it?
Is it current and relevant?
What do independent sources say?
What is the bias or conflict of interest?
Is it a primary or secondary source?
Does it deserve a place in my argument?

Final thoughts

Evaluating sources is a habit more than a test. Ask who is speaking, what they know, why they are saying it and what other sources say. Read laterally, check the evidence and keep your judgment visible in your writing. A short note on a source's strengths and limits shows readers that you used it thoughtfully.