Guide
Types of peer review
Peer review comes in several models that differ mainly in who knows whose identity and when the review happens — from single-anonymous to open, transparent and post-publication review.
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What the models vary on
Peer review is the evaluation of a manuscript by independent experts, but journals run it in several ways, and the models differ along two main axes: who knows whose identity, and when the review takes place. Traditionally identities were concealed to reduce bias; more recent models open them up to increase accountability and credit. Understanding the variants matters for authors choosing where to submit and for readers judging how a paper was assessed. COPE provides ethical guidance that applies across all of these models.
Single- and double-anonymous review
In single-anonymous review — long the most common model — the reviewers know who the authors are, but the authors do not know who reviewed them. This protects reviewers from pressure but can let conscious or unconscious bias about an author’s identity, institution or reputation influence the assessment. Double-anonymous review conceals both parties: reviewers do not learn the authors’ identities and vice versa. It aims to focus judgement on the work itself and reduce bias relating to gender, seniority or affiliation, though authors can sometimes be guessed from the content, self-citations or topic.
Open and transparent review
Open peer review is an umbrella term for models that lift the veil of anonymity. In its fullest form, reviewers and authors know each other’s identities, and the review reports — sometimes signed — are published alongside the article. Transparent peer review specifically publishes the reviewer reports, the authors’ responses and the editorial decisions with the paper, even where reviewers remain anonymous. The aim is accountability and credit: reviewers can be recognised for their work, readers can see how conclusions were scrutinised, and the review process itself becomes part of the scholarly record.
Post-publication review and registered reports
Two models change the timing of review. Post-publication peer review continues the evaluation after an article is released — through formal commenting platforms, preprint annotation or letters — recognising that scrutiny does not end at publication. Registered reports invert the usual order: the introduction and methods are peer-reviewed before data collection, and a study that passes this Stage 1 review receives in-principle acceptance regardless of how the results turn out. By reviewing the question and design rather than the findings, registered reports curb publication bias and discourage outcome-driven practices.
Key facts
At a glance
- Varies on: who knows whose identity, and when review happens
- Single-anonymous: reviewers know authors; authors do not know reviewers
- Double-anonymous: both authors and reviewers are concealed from each other
- Open: identities revealed; reports may be published, sometimes signed
- Transparent: reviewer reports and responses published with the article
- Registered reports: methods reviewed before results exist, curbing publication bias
Common questions
FAQ
What is the difference between single- and double-anonymous peer review?+
In single-anonymous review the reviewers know who the authors are while the authors do not know the reviewers. In double-anonymous review both are concealed from each other. Double-anonymous review aims to reduce bias linked to an author’s identity, institution or seniority by focusing attention on the work itself, although authors can occasionally be inferred from the content or self-citations.
What is open peer review?+
Open peer review is an umbrella term for models that reduce anonymity. It can mean reviewers and authors know each other’s identities, that the reviewer reports are published with the article, or both — and reports are sometimes signed. Its goals are accountability, recognising reviewers for their work, and letting readers see how a paper’s conclusions were scrutinised.
What are registered reports?+
Registered reports are a format in which a study’s introduction and methods are peer-reviewed before any data are collected. If the plan passes this Stage 1 review the journal grants in-principle acceptance, committing to publish the completed study whatever the results. By evaluating the question and design rather than the findings, registered reports reduce publication bias and discourage outcome-driven analysis.
