Reviewing manuscripts from paper mills: Red flags and how to respond

Paper mills, commercial operations that produce and sell scientific manuscripts, authorship slots, and in some cases manufactured peer review outcomes, represent one of the most serious systemic threats to research integrity in contemporary publishing. The Committee on Publication Ethics (COPE) and major publishers have identified paper mills as a deeply embedded vulnerability. COPE and the International Association of Scientific, Technical and Medical Publishers (STM) also introduced the United2Act coalition in 2024 to initiate coordinated action to address the problem at scale. As a peer reviewer, you may encounter paper mill products without realizing it. In this post, we talk about paper mills to help you identify them, especially when you think you are dealing with the product of a paper mill as a peer reviewer.

What paper mills are and why they matter

Paper mills operate as commercial services selling a range of products. Wiley defines them as “the process by which manufactured manuscripts are submitted to a journal for a fee on behalf of researchers with the purpose of providing an easy publication for them, or to offer authorship for sale.” Paper mill products include fabricated, submission-ready manuscripts for sale, slots for authors who want to purchase authorship, or introductions to reviewers who will provide favorable assessments. Some operate openly in certain research ecosystems, while others are deliberately obscured. Their manuscripts are often produced using templates, generic text that can be adapted for different target journals and disciplines, and recycled images, data, and content.

Researchers build their work on previously published work, and when the products of paper mills are cited in the literature, they become part of the existing knowledge in the field. This could have serious consequences in fields like clinical medicine, where they can contribute to evidence bases that inform patient care decisions. Importantly, paper mill products sometimes use real researchers’ names and institutional affiliations without their knowledge or prior consent.

Red flags in manuscript content

Reviewers who have examined paper mill manuscripts across multiple investigations have identified consistent content-level warning signs:

1. Image and data irregularities: Here’s what you should look out for

• Western blot, microscopy, or flow cytometry images that appear duplicated, spliced, or inconsistent with described experimental conditions
• Results that are implausibly clean
• Very tight standard deviations
• Suspiciously round numbers
• Effect sizes that do not vary across conditions

1. Generic or incoherent methods: Methods sections in paper mill products are often vague, templated, or internally inconsistent with the reported results. You may notice that

• The described procedure does not match what would actually produce the reported data
• The language reads as if assembled from standard phrases rather than describing actual laboratory practice
• Specific reagent names, equipment models, or parameter settings are missing or implausibly generic for the level of detail claimed elsewhere in the paper

2. Topic-author mismatch: A mismatch between the stated research topic and the plausible research interests or institutional context of the listed authors is a common paper mill signal. Authors from a single institution who collectively span implausibly diverse and unrelated specialties, or a paper on a highly specialized topic authored by people with no apparent publication record in the area can indicate that authorship was purchased rather than earned.
3. Incoherent reference lists: Large numbers of self-citations unrelated to the topic, citations to papers that do not appear relevant to the argument, or reference lists that include a suspiciously consistent set of authors across papers in the same submission batch are signals associated with paper mill products designed to game citation metrics.
4. Submission metadata: Some paper mill signals appear at the level of submission metadata rather than manuscript content:

• Free webmail addresses for authors who list institutional affiliations, particularly when other aspects of the paper suggest professional researchers. Most institutions provide email addresses; use of Gmail or Yahoo alongside a university affiliation is unusual. However, remember that this is not always a red flag. Often, independent researchers use their personal email addresses,
• Unrealistically high individual publication rates for listed authors, or publication lists that span very diverse, unrelated fields. Both observations could signal that a name is being used across paper mill products rather than reflecting genuine research output.
• Suggested reviewers whose institutional email addresses are unusual, who return no verifiable academic profile, or whose names are shared with different people across submission databases.
• Unusually rapid revision and resubmission cycles – a major revision returned within days can indicate that responses were prepared in advance rather than reflecting genuine engagement with review comments.

The role of peer reviewers in dealing with the output of paper mills

If you suspect that you are reviewing a manuscript created by a paper mill, share your concerns with the editor separately, not in the main review that would be visible to the authors. Be specific about what you observed: which elements of the manuscript or submission raised suspicion, and why. Useful things to flag include:

• Specific image irregularities
• Methods inconsistencies
• Implausible author-topic combinations
• Unusual submission metadata.

The more specific your observations, the more actionable they are for the editor.

Journals typically use detection tools and cross-reference against known paper mill patterns and databases. Several publishers now have dedicated research integrity teams for this purpose. Despite these measures, it is not uncommon for paper-mill created manuscripts to go through these checks and reach peer review. This is where you step in. Your role is to raise the concern clearly and leave the investigation and follow-ups with the journal.

You should complete your assessment of the manuscript, even if you are raising a paper-mill-related concern. The two are parallel processes: editors need your scientific evaluation as well as your integrity concern. This will help them make clear decisions about rejection on ethical grounds.

Remember: Knowing that paper mills exist should make you a cautious and alert peer reviewer, not one who is paranoid about every manuscript you receive.

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