Table 3. Pros and cons of different approaches to anonymity in peer review.

Approach	Description	Pros/Benefits	Cons/Risks	Examples
Single blind peer review	Referees are not revealed to the authors, but referees are aware of author identities	Allows reviewers to view full context of an author’s other work, detection of COIs, more efficient	Prone to bias, authors not protected, exclusive, non-verifiable, referees can often be identified anyway	Most biomedical and physics journals, PLOS ONE, Science
Double blind peer review	Authors and the referees are reciprocally anonymous	Increased author diversity in published literature, protects authors and reviewers from bias, more objective	Still prone to abuse and bias, secretive, exclusive, non- verifiable, referees can often be identified anyway, time consuming	Nature, most social sciences journals
Triple-blind peer review	Authors and their affiliations are reciprocally anonymous to handling editors and reviewers	Eliminates geographical, institutional, personal and gender biases, work evaluated based on merit	Incompatible with pre- prints, low-uptake, non- verifiable, secretive	Science Matters
Private, open peer review	Referee names are revealed to the authors pre-publication, if the referees agree, either through an opt-in or opt-out mechanism	Protects referees, no fear of reprisal for critical reviews	Increases decline to review rates, non- verifiable	PLOS Medicine, Learned Publishing
Unattributed peer review	If referees agree, their reports are made public but anonymous when the work is published	Reports publicized for context and re-use	Prone to abuse and bias similar to double blind process, non-verifiable	EMBO Journal
Optional open peer review	As single blind peer review, except that the referees are given the option to make their review and their name public	Increased transparency	Gives an unclear pictures of the review process if not all reviews are made public	PeerJ, Nature Communications
Pre-publication open peer review	Referees are identified to authors pre-publication, and if the article is published, the full peer review history together with the names of the associated referees is made public	Transparency, increased integrity of reviews	Fear: referees may decline to review, or be unwilling to come across too critically or positively	The medical BMC-series journals, The BMJ
Post-publication open peer review	The referee reports and the names of the referees are always made public regardless of the outcome of their review	Fast publication, transparent process	Fear: referees may decline to review, or be unwilling to come across too critically or positively	F1000Research, ScienceOpen, PubPub, Publons
Peer review by endorsement (PRE)	Pre-arranged and invited, with referees providing a “stamp of approval” on publications	Transparent, cost- effective, rapid, accountable	Low uptake, prone to selection bias, not viewed as credible	RIO Journal