Post-publication peer review (PPPR) is scrutiny of a published article that happens after formal editorial acceptance — on independent commentary platforms, in preprint-server comment threads, on social media, or built directly into a journal’s publishing model. What discussion of PPPR usually skips is the second half of the story: a concern raised in public doesn’t change the scholarly record by itself. That only happens once it passes through a specific, standards-based editorial and infrastructure pathway — and that pathway, not the discussion layer, is what determines whether anyone who cites, indexes, or reads the original article ever finds out something changed.
What post-publication peer review covers, and what it doesn’t decide
PPPR takes several forms. Independent commentary platforms — PubPeer is the best known — let anyone post comments against a paper identified by its DOI or PubMed ID, commonly flagging statistical anomalies, image irregularities, or methodological concerns; PubPeer is run by the PubPeer Foundation, a nonprofit registered in the United States, and operates independently of any publisher, journal, or standards body, CASRAI included. Preprint servers carry similar commenting features on the preprint itself. A smaller number of journals build ongoing review into the publishing model from the start — F1000Research, Open Research Europe, and (since a 2023 policy change) eLife all publish a reviewed work alongside its public reviews rather than gating publication behind an accept/reject decision.
None of this, on its own, is a correction. A published article’s text, and its DOI’s registered metadata, do not change because a PubPeer thread exists or because a blog post raises a serious question. That requires a separate step: a publisher or journal decision, made through a defined editorial process, resulting in one of a small set of formal outcomes — a correction (corrigendum), an expression of concern, or a retraction.
From a raised concern to a formal correction: the editorial pathway
The Committee on Publication Ethics (COPE) is the reference body most journals point to for how this investigation should run, alongside a separate COPE guideline covering expressions of concern specifically. In outline: a concern is raised (through PubPeer, direct correspondence to the editor, an institutional research-integrity office, or a journal’s own screening), the publisher or journal investigates — sometimes with the author’s institution — and, if the concern is substantiated, issues one of the outcomes above. Crucially, none of these is a silent edit to the original PDF or HTML. Crossref’s own documentation on registering updates is explicit that publishers “will not modify the original document” — instead they issue a separate document, with its own distinct DOI, that explains the change and is formally linked back to the original.
How the change actually propagates: Crossref’s Crossmark service
This is the mechanical layer most explainers of PPPR skip entirely, and it’s the part a standards body is best placed to describe precisely. Crossmark is the Crossref service built specifically for this: participating publishers place a Crossmark button next to the title of an article, on both the web page and the PDF, and commit to registering any correction, expression of concern, or retraction with Crossref as it happens. That registration goes into an update-to field in the article’s Crossref metadata record, linking the original DOI to the new document’s DOI, its type (correction, retraction, etc.), and a date. Anyone — a reader, a reference manager, a discovery layer, another publisher’s own system — can query that metadata against the DOI and see the current status, without relying on the original page having been revisited or the PDF having been redownloaded. Because the button is embedded in the PDF itself, this works even years after a copy was first saved to someone’s hard drive.
Since September 2023, this same mechanism carries more than publisher self-reporting. Crossref acquired the Retraction Watch database — an independently curated index of retractions maintained by the Center for Scientific Integrity — and folded it into the same update-to field in its REST API, tagged by source as either publisher or retraction-watch. Retraction Watch itself remains an independent editorial operation (best known for its retraction-tracking blog and database, not affiliated with CASRAI); what changed in 2023 is that its findings now feed the same standardised, DOI-anchored metadata graph that Crossmark exposes — so a retraction Retraction Watch identified independently, even one a publisher was slow to register itself, becomes visible through the same programmatic channel as a publisher-registered one. That combination — real-time publisher self-reporting plus an independently curated backstop, both keyed to the DOI — is what makes the correction discoverable systematically rather than depending on a reader happening to check the right commentary site.
Does it reach a researcher’s ORCID record?
The honest answer has more nuance than most explainers allow. An ORCID record’s works list is built around the same identifier: works are added either manually by the researcher or through Crossref’s auto-update integration, which — once a researcher grants permission via a notification in their ORCID inbox — automatically adds any future work registered with Crossref that carries their ORCID iD in its metadata. A correction or retraction notice is itself a separately registered document with its own DOI, so where that notice’s metadata carries the relevant author’s ORCID iD, the same auto-update channel that adds new publications to a record is the pathway by which the notice itself can appear there too.
What CASRAI cannot confirm from ORCID’s own published documentation is a specific, automatic visual indicator — a “retracted” badge — appearing on an already-listed work inside a researcher’s ORCID record the moment a retraction is registered elsewhere. The verified mechanism is the identifier chain, not a guaranteed profile-level flag: the original article’s DOI, the correction or retraction notice’s own DOI, and the researcher’s ORCID iD are all linked through the same Crossref metadata graph that Crossmark and the Retraction Watch integration populate. Any system — including ORCID’s own auto-update pipeline — that queries live Crossref metadata for that DOI can act on the current status. Whether a specific interface surfaces that as a visible flag is a matter of that system’s own design, and worth checking directly against ORCID’s current interface rather than assuming.
What a typical post-publication review sequence looks like
The following is a generic, illustrative sequence of how a concern moves through this pathway — not a description of any specific real article, journal, or researcher. A commenter identifies what looks like a duplicated image panel in a published figure and posts it, with the DOI, to an independent commentary platform. The journal’s editorial office is alerted (either directly or because the platform’s policy is to notify the journal) and opens an internal review, consulting COPE’s retraction guidelines and, if it involves possible misconduct, the author’s institution. If the office decides the concern is serious enough to flag publicly while it investigates, it publishes an expression of concern — a short, separately DOI-registered notice linked to the original article — and registers that update with Crossref so the Crossmark badge on the original reflects it immediately. If the investigation later substantiates the concern, that expression of concern is superseded by a full retraction notice, again separately registered, again linked back through the same update-to metadata.
Frequently asked questions
Is PubPeer affiliated with CASRAI or with any journal?
No. PubPeer is an independent nonprofit platform (the PubPeer Foundation) with no formal affiliation to CASRAI, any individual journal, or any publisher. It is one channel through which post-publication concerns are raised, not a body that issues corrections or retractions itself — that remains the responsibility of the journal or publisher.
Is Retraction Watch the same as Crossref?
No, though the two are now formally connected. Retraction Watch is an independent editorial project (run by the Center for Scientific Integrity) that has curated a database of retractions since 2018. In September 2023, Crossref acquired that database and integrated its data into Crossref’s own metadata (via the same update-to field used for Crossmark), while Retraction Watch continues to maintain and grow the underlying data.
Does post-publication peer review replace pre-publication peer review?
No. Even journals that have adopted a publish-review-curate model still run structured peer review before or immediately around publication — they’ve changed when an accept/reject gate applies, not whether review happens. PPPR is best understood as an additional, ongoing layer of scrutiny that continues after formal publication, not a replacement for review that already occurred.
How long does it take for a correction to show up via Crossmark?
There’s no fixed timeline in Crossref’s documentation — it depends on how quickly the publisher registers the update after its own editorial process concludes. The mechanism itself (the update-to field, exposed via the Crossref API and the Crossmark badge) is near-immediate once registered; the bottleneck is the editorial investigation that precedes registration, not the propagation step.
