“Is that peer-reviewed?” is one of the most common questions supervisors ask during thesis reviews — and one of the most poorly answered. Many students assume that anything with a DOI, or anything they find on Google Scholar, has been reviewed. Neither is true. This guide shows you how to correctly classify a source in about two minutes, before you add it to your bibliography.
What peer review actually is (and isn’t)
Peer review means: a manuscript is read, critiqued, and given a publication recommendation — accept, revise, or reject — by at least two independent domain experts before publication. In most fields the process runs double-blind: reviewers don’t know the authors, authors don’t know the reviewers.
What does not count as peer review:
- A publisher’s copy-editing pass (spelling, layout) is not peer review.
- Editorial approval by the editors alone is not peer review.
- A post-publication comment system doesn’t count as classic peer review in most disciplines.
- Conference abstracts are rarely peer-reviewed; full conference papers often are.
This distinction matters because many universities explicitly ask you to “prefer peer-reviewed sources” — some even prescribe a minimum share.
Why the question got harder in 2026
Ten years ago, peer review was binary: journal or not. Today five publication forms coexist, and each has reviewed and unreviewed content:
- Traditional journals — standard peer review.
- Conference proceedings — varies by field; in computer science often stricter than journals.
- Preprint servers (arXiv, bioRxiv, SSRN, medRxiv) — not peer-reviewed. Authors upload manuscripts directly.
- Working papers from institutes (NBER, CEPR, IZA) — usually no external review, sometimes internally vetted.
- Open-access megajournals (PLoS ONE, Scientific Reports) — peer-reviewed, but with a lower bar for “novelty.”
On top of that, predatory journals claim peer review without running one. And even reputable journals publish editorials or letters alongside their peer-reviewed articles — themselves not reviewed.
The seven-step check
Run every doubtful source through these seven points. Two minutes each.
1. Check the article type in the full text
Open the full text (not the abstract) and look for the article type in the header. Serious journals label it clearly:
- Original Article / Research Article / Original Paper — peer-reviewed.
- Review Article / Systematic Review / Meta-Analysis — peer-reviewed.
- Editorial / Commentary / Letter to the Editor / Opinion / Perspective — mostly not peer-reviewed.
- Book Review / News / Correspondence — not peer-reviewed.
- Erratum / Corrigendum — not a standalone article.
If the type is missing, that alone is a soft warning sign.
2. Check Ulrichsweb
Ulrichsweb (ulrichsweb.com) is the largest database of journal metadata. It has a dedicated “Refereed / Peer-Reviewed” symbol — a striped referee shirt. If your journal carries that symbol, it is structurally set up for peer review. Ulrichsweb doesn’t tell you anything about a specific article though — editorials in a peer-reviewed journal are still not peer-reviewed.
Access is usually through your university library.
3. The journal’s “Instructions for Authors”
Every credible journal has an “Instructions for Authors” or “Author Guidelines” page. Look for the section on “Peer Review Process” or “Editorial Policy.” Clear statements like “double-blind peer review by at least two independent reviewers” are a good sign. Vague wording (“editorial review”) or missing information is a warning.
4. Check DOAJ (for open access)
For open-access journals: search the journal in doaj.org. The DOAJ entry lists whether and how peer review is performed. If a journal is open access but not in DOAJ, that’s an additional warning sign (see also Recognizing predatory journals).
5. Indexation in Scopus or Web of Science
Scopus and Web of Science Core Collection admit journals only after quality vetting. Indexation isn’t a guarantee that every single article is peer-reviewed, but it’s a strong signal of structural seriousness. Check directly on scopus.com (Journal Finder) or mjl.clarivate.com (Master Journal List).
6. Identify the publication version
A common mistake: you have a preprint in hand but think you’re reading the journal version. Watch for:
- arxiv.org, biorxiv.org, ssrn.com, researchgate.net, preprints.org — almost always preprints. Not peer-reviewed.
- Author Manuscript / Accepted Manuscript — the manuscript version after peer review but before publisher production. Content is post-review, but the final Version of Record is preferable.
- Version of Record (VoR) — the final typeset version published in the journal. Cite this whenever possible.
Check the URL, the watermark, and the header line on each PDF.
7. For conference papers: program committee, not journal
For conference proceedings the check runs differently: look up the program committee (PC) and the review-process description in the conference programme. Some conferences (NeurIPS, CHI, ACL) run stricter review than most journals. Others accept nearly everything. Rule of thumb: an acceptance rate below 40 % means the review is real.
Grey areas — the most common confusions
Three cases turn up in almost every supervision meeting.
A DOI is not a peer-review badge
A DOI (Digital Object Identifier) identifies a digital object. Preprint servers, university repositories, and datasets all mint DOIs without any review. A DOI only proves that the object has been archived and is citable — nothing more.
“In peer review” or “under review” does NOT mean peer-reviewed
A manuscript with the status “under review” is in the review process but not yet accepted. Cite such work only with a “unpublished” or “under review” qualifier — and only if you can’t find a better source.
Google Scholar says nothing about peer review
Google Scholar indexes everything that looks scholarly: preprints, working papers, master’s theses, conference abstracts, predatory-journal articles. A Scholar hit means “found,” not “vetted.” Use Scholar to discover, not to evaluate.
What to do with non-peer-reviewed sources
Not every unreviewed source is worthless — in some fields (economics, computer science, physics) working papers and preprints are standard. Three rules make them citable:
- Label the type. In the text or a footnote, write “preprint” or “working paper” so it’s clear the source hasn’t gone through peer review.
- Check whether a journal version exists. Preprint servers link to the final version once published. If a journal version is available, cite it instead of the preprint.
- Don’t use them for central claims. For minor points or the state of the field, preprints are fine. For the central theses of your work you need peer-reviewed evidence.
Peer review or not — what counts is what you make of the source
Peer review answers exactly one question: did independent experts consider the paper methodologically sound? What it does not tell you: whether the claim you cite from the paper is actually in there.
Three observations from practice:
- Retracted papers keep getting cited. Retraction studies show time and again that retracted articles are cited for years as if they were still valid. The peer review is long done; the finding is gone anyway.
- Even unchallenged papers get cited wrongly. The page number is off, the claim comes from the discussion section of a different paper, or a cautiously phrased observation gets inflated into an established fact.
- And the reverse: the strongest, properly reviewed paper does nothing for you if you claim something it doesn’t support.
Peer-review status is a necessary check, not a sufficient one. Journal prestige says something about where a source comes from — nothing about whether you use it correctly.
How to automate the second check
Acurio does exactly this check: instead of asking where a paper appeared, it compares every claim in your document against the source you actually cite.
- Upload your document — your thesis including its bibliography, no preparation needed.
- Automatic verification — for every citation: does the source exist? Does it support the claim? Is the page number right?
- Findings per citation — you get a result for each citation and can fix targeted problems instead of re-reading the whole bibliography by hand.
Just as important is what Acurio does not do: it doesn’t rate the quality of the source itself, it replaces neither your own reading nor your supervisor’s judgment — and it doesn’t check whether a journal is peer-reviewed. That part stays with you and the seven steps above.
If you only want a rough test of your bibliography first, you can do that without uploading anything or signing up in the Quick Check: paste your bibliography, run the check, done.
Bottom line: two minutes of checking, a lot less pain
Verifying peer review isn’t librarian work — it’s two minutes per source once you know where to look. In order:
- Article type in the full text (Article? Editorial?).
- Ulrichsweb or DOAJ for the journal.
- “Instructions for Authors” for the actual process.
- Publication version (preprint? Version of Record?).
Build the check into your reference-manager routine — in Zotero, for instance, as a “peer-review verified” tag. By the end of your thesis you’ll know for every source what you’re citing and why.
The second quality check — whether your citations are actually supported by the sources — is covered in the section above. Peer review and citation verification are two separate quality gates — together they give you the confidence that your bibliography will withstand your first reviewer’s scrutiny.