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Guidelines for Reviewers

“We are sincerely grateful to scholars who give their time to peer-review articles submitted to MDPI journals. Rigorous peer-review is the corner-stone of high quality academic publishing.”
— The MDPI editorial team.

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Reviewer Guides

1. Peer Review and the Editorial Procedure

Peer review is an essential part of the publication process, and it ensures that MDPI maintains the highest standards for its papers. All manuscripts submitted to our journals are strictly and thoroughly peer-reviewed by experts.

Immediately after submission, the journal’s Managing Editor performs a technical pre-check of the manuscript. A suitable Academic Editor is notified of the submission and invited to perform an editorial pre-check and recommend reviewers. The Academic Editor can decide to continue with the peer review process, reject the manuscript, or request revisions before peer review. If continuing the peer review process, the Editorial Office organizes the peer review, who are independent experts, and collects at least two review reports per manuscript. We ask authors to make sufficient revisions (with a second round of peer review when necessary) before a final decision is made. The final decision is made by an Academic Editor (usually the Editor-in-Chief/Editorial Board Member of a journal or the Guest Editor of a Special Issue). Accepted manuscripts then undergo internal copy-editing and English editing. More details about the editorial process can be found here. A brochure for reviewers can be found here.

2. Reviewers’ Profiles and Responsibilities

The role of the reviewer is vital, and they bear a great responsibility in ensuring the integrity of the scholarly record. Every reviewer is expected to evaluate manuscripts in a timely, transparent, and ethical manner, following the COPE guidelines (https://publicationethics.org/guidance/guideline/ethical-guidelines-peer-reviewers).

Reviewers should meet the following criteria:

  • They should have no conflicts of interest with any of the authors;
  • They should not be part of the same institution as the authors;
  • They should not have published with the authors in the past three years;
  • They should hold a PhD or MD (applicable for medical journals);
  • They should have relevant experience and a proven publication record in the field of the submitted paper (accessible through Scopus or ORCID);
  • They should be experienced scholars in the field of the submitted paper;
  • They should hold an official and recognized academic affiliation.

MDPI requires rigorous peer review to ensure the thorough evaluation of each manuscript; this is a fundamental task for our reviewers. Reviewers are expected to meet the following requirements:

  • They must have the necessary expertise to judge the scientific quality of manuscripts;
  • They need to provide high-quality review reports and remain responsive throughout the peer review process;
  • They must maintain standards of professionalism and ethics.

3. Reviewers’ Benefits

Reviewing is a crucial yet often unseen and unrewarded task. We are committed to recognizing the efforts of all our reviewers.

Reviewing for MDPI journals includes the following benefits:

  • For every manuscript reviewed, the reviewer may receive a discount voucher code entitling them to a reduction in the article processing charge (APC) of a future submission to any MDPI journal. This voucher is linked to the reviewer’s email address and can be applied online during submission or at any time before the manuscript is accepted. Note that vouchers cannot be used after an invoice has been issued upon the acceptance of a manuscript. If an article is rejected, the voucher can instead be used for a future submission. Please note that reviewer vouchers can only be combined with IOAP and affiliated society discounts.
  • Reviewer voucher codes can be used to pay for professional English editing through Author Services.
  • Reviewers receive a personalized reviewer certificate.
  • Reviewers are eligible to be considered for the Outstanding Reviewer Awards.
  • Reviewers are included in a journal’s annual acknowledgment of reviewers if more than 50 reviewers assisted the journal in the previous year.
  • Excellent reviewers may be promoted to Reviewer Board Members (subject to approval by the Editor-in-Chief).
  • Reviewers may create a profile on the Web of Science Reviewer Recognition Service (formerly Publons) and have their reviewing activity automatically added for participating journals; these profiles can also be integrated with ORCID.

4. Reviewer Board

The Reviewer Board (RB) consists of experienced researchers whose main responsibility is to regularly and actively support journals by providing high-quality, rigorous, and transparent review reports for submitted manuscripts within their area of expertise. The initial term is 1 year and can then be renewed or terminated. Membership involves the same responsibilities and benefits as those for regular reviewers, with the addition of the following:

  1. RB Members must review a minimum of six manuscripts per year. Should the reviewer be unable to provide a report when invited, they are expected to suggest alternative potential reviewers (the proposed candidates must meet the reviewers’ requirements from Section 2).
  2. RB Members are entitled to receive an RB certificate.
  3. RB Members are announced on the journal website.

5. Volunteer Reviewers

MDPI journals are actively looking for volunteers to review manuscripts. MDPI’s Reviewer Board Members and Volunteer Reviewers can offer to review articles in one or more of MDPI’s journals.

To become part of this program, you must fulfil the criteria outlined in Section 2 entitled “Reviewers’ Profiles and Responsibilities”.

To become a member of this program, please apply here. The Editorial Office of the selected journal will be notified and your application will be reviewed by our internal staff, who will verify that your background suits the scope of the journal and address any potential ethical issues. Should you pass our internal check, your application will be approved.

Active Volunteer Reviewers may be promoted to Reviewer Board Members (subject to approval by the Editor-in-Chief).

6. General Guidelines for MDPI’s Reviewer Recruiting Program

To apply to review a manuscript as a Reviewer Board Member or Volunteer Reviewer, you can visit the “Recruiting Reviewers” menu in our Submission System (SuSy) (https://susy.mdpi.com/reviewer/list/recruiting_reviewers_manuscripts), which is visible on the left-hand side under “Reviewers Menu”. Here, you can see all the manuscripts that you can apply for*. You can search by journals and keywords. Should you find a manuscript that you would like to review, please click on “Apply”. The Editorial Office of the respective journal will be notified about your application, and our internal staff will inspect your research background and address any potential conflicts of interest. Should you pass, your application to review will be approved.

* Please note that you can only see and apply to manuscripts in journals for which you are a Reviewer Board Member or Volunteer Reviewer.

7. General Guidelines for Reviewers

7.1. Invitation to Review

Manuscripts submitted to MDPI journals are reviewed by at least two experts, who can be Volunteer Reviewers, Reviewer Board Members, or reviewers suggested by the Academic Editor during the preliminary check. The reviewers are asked to evaluate the quality of the manuscript and provide a recommendation to the external editor on whether the manuscript should be accepted, requires revisions, or should be rejected.

We ask invited reviewers to do the following:

  • Accept or decline any invitations at their earliest convenience (based on the manuscript’s title and abstract);
  • Suggest alternative reviewers if an invitation must be declined;
  • Promptly request a deadline extension if more time is required to provide a comprehensive report.

7.2. Potential Conflicts of Interest

We ask reviewers to declare any potential conflicts of interest and email the journal’s Editorial Office if they are unsure if something constitutes a potential conflict of interest. Possible conflicts of interest include (but are not limited to) the following:

  • The reviewer works at the same institute as one of the authors;
  • The reviewer has been a co-author, collaborator, or joint grant holder or has had any other academic link with any of the authors within the past three years;
  • The reviewer has a close personal relationship with, rivalry with, or antipathy to any of the authors;
  • The reviewer may financially gain or lose from the publication of the paper in any way;
  • The reviewer has any other non-financial conflicts of interest (political, personal, religious, ideological, academic, intellectual, or commercial, among others) with any of the authors.

Reviewers should disclose any conflicts of interest that may be perceived as bias for or against the paper or authors.

Please kindly note that if reviewers are asked to assess a manuscript they previously reviewed for another journal, as this is not considered a conflict of interest. In this case, reviewers should feel free to let the Editorial Office know if the manuscript has been improved or not compared to the previous version.

Reviewers are also advised to read the relevant descriptions in the Ethical Guidelines For Peer Reviewers from the Committee on Publication Ethics (COPE).

7.3. Declaration of Confidentiality

MDPI journals operate single- or double-blind peer review (https://www.mdpi.com/editorial_process). Until an article is published, the reviewers should keep the content of the manuscript, including the abstract, confidential. The reviewers should also be careful to not reveal their identity to the authors, either in their comments or in metadata for reports submitted in Microsoft Word or PDF format. Reviewers must inform the Editorial Office if they would like a colleague to complete the review on their behalf (reviewers should always meet the criteria reported in Section 2).

MDPI journals offer the opportunity for authors to publish review reports together with their paper (open peer review) and for reviewers to sign their open peer review reports once “Open Peer Review” (https://www.mdpi.com/editorial_process) has been selected by the authors. However, this will only be carried out upon publication with the reviewers’ permission. In all other cases, review reports are considered confidential and will only be disclosed with the explicit permission of the reviewers.

7.4. Review Reports

Review reports must be written in English. We list some general instructions regarding review reports below.

To begin with, please consider the following guidelines:

  • Reviewers should read the whole article as well as the Supplementary Materials, if applicable, paying close attention to the figures, tables, data, and methods.
  • Reviewers should critically analyze the article as a whole, in addition to specific sections and the key concepts presented.
  • Comments should be detailed so that the authors may correctly understand and address the points raised.
  • Reviewers must not recommend excessive citations of their work (self-citations), another author’s work (honorary citations), or articles from the journal to which the manuscript was submitted as a means of increasing the number of citations of the reviewer/author/journal. References can be provided as needed, but they must clearly improve the quality of the manuscript under review.
  • Reviewers should maintain a neutral tone and focus on providing constructive criticism that will help the authors improve their manuscript. Derogatory comments will not be tolerated.
  • GenAI tools and other large language models (LLMs) should not be used by reviewers in the preparation of review reports. Reviewers are solely responsible for the content of their reports, and the utilization of these tools may violate confidentiality, proprietary, and data privacy rights. Limited use to improve the written quality of a peer-review report, such as correcting grammar, structure, spelling, punctuation and formatting, may be acceptable but should be disclosed upon the submission of the peer-review report. Under no circumstances should reviewers upload manuscripts, either in whole or in part, images, figures, tables or any kind of communication related to unpublished manuscripts to any GenAI tools, as to do so violates MDPI’s confidentiality policy relating to peer-review. If it is determined that AI tools have been inappropriately used in the preparation of a review report, the report will be discarded.

Note that MDPI journals follow several standards and guidelines, including those from the ICMJE (medical journals), CONSORT (reporting trials), TOP (data transparency and openness), PRISMA (systematic reviews and meta-analyses), and ARRIVE (reporting in vivo experiments). See the Publishing Standards and Guidelines page or contact an Editorial Office for more details. Reviewers that are familiar with these guidelines should report any concerns they have about their implementation.

For further guidance on writing a critical review, please refer to the following documents:

  1. COPE Ethical Guidelines for Peer Reviewers. Committee on Publication Ethics. Available online.
  2. Hames, I. Peer Review and Manuscript Management in Scientific Journals: Guidelines for Good Practice. Wiley-Blackwell: Oxford, UK, 2007.
  3. Writing a journal article review. Australian National University: Canberra, Australia, 2010. Available online.
  4. Golash-Boza, T. How to write a peer review for an academic journal: Six steps from start to finish. Available online.

Review reports should contain the following:

  • A brief summary (one short paragraph) outlining the aim of the paper, its main contributions, and its strengths.
  • Comments regarding general concepts
    Articles: Comments highlighting areas of weakness, the testability of the hypothesis, methodological inaccuracies, missing controls, etc.
    Reviews: Comments on the completeness of the topic covered, its relevance, the identified gap in knowledge, the appropriateness of references, etc.
    These comments should be focused on the scientific content of the manuscript and should be specific enough for the authors to suitably respond.
  • Specific comments referring to line numbers, tables or figures that disclose inaccuracies within the text, or sentences that are unclear. These comments should also focus on the scientific content rather than on spelling, formatting, or errors in the English language, as these will be addressed at a later stage by our internal staff.

Below are general questions to help guide the writing of review reports for research articles:

  • Is the manuscript clear, relevant to the field, and presented in a well-structured manner? 
  • Are most of the cited references recently published (within the last 5 years) and relevant? Does the manuscript include an excessive number of self-citations?
  • Is the manuscript scientifically sound, and is the experimental design appropriate to test the hypothesis?
  • Are the manuscript’s results reproducible based on the details given in the Methods section?
  • Are the figures/tables/images/schemes appropriate? Do they properly present the data? Are they easy to interpret and understand? Are the data interpreted appropriately and consistently throughout the manuscript? (Please include details regarding the statistical analysis or data acquired from specific databases.)
  • Are the conclusions consistent with the evidence and arguments presented?
  • Are the ethics and data availability statements adequate?

Below are general questions to help guide the writing of review reports for review articles:

  • Is the review clear, comprehensive, and relevant to the field? Are there any gaps in knowledge?
  • Has a similar review been published recently and, if yes, is the current review still relevant and of interest to the scientific community?
  • Are most of the cited references recently published (within the last 5 years) and relevant? Are any relevant citations omitted? Does the manuscript include an excessive number of self-citations?
  • Are the statements and conclusions drawn coherent and supported by the listed citations?
  • Are the figures/tables/images/schemes appropriate? Do they properly present the data? Are they easy to interpret and understand?

The content of the review report will be rated by an Academic Editor from a scientific point of view  to determine its general usefulness for the improvement of the manuscript. Overall grading results will be used as a reference for the potential promotion of Reviewer Board Members, Volunteer Reviewers, and regular reviewers.

7.5. Rating Manuscripts

During the manuscript evaluation, please rate the following aspects:

  • Novelty: Is the research question original and well defined? Do the results advance the current knowledge?
  • Scope: Does the manuscript fit the journal’s scope*?
  • Significance: Are the results interpreted appropriately? Are they significant? Are all conclusions justified and supported by the results? Are hypotheses carefully identified?
  • Quality: Is the article written in an appropriate way? Are the data and analyses presented effectively? Are the highest standards used for the presentation of the results?
  • Scientific Soundness: Is the study correctly designed and technically sound? Are the analyses performed according to the highest technical standards? Are the data robust enough to draw conclusions? Are the methods, tools, software, and reagents described with sufficient details to allow other researchers to reproduce the results? Are the raw data available and correct (where applicable)?
  • Interest to Readers: Will the conclusions engage the journal’s readers? Will the paper attract a wide readership or be of interest only to a limited number of people? (Please refer to the aims and scope of the journal.)
  • Overall Merit: Is there an overall benefit to publishing this research? Does the manuscript advance the current knowledge? Do the authors address a significant long-standing question with innovative experiments? Do the authors present a negative result for a valid scientific hypothesis?
  • English Level: Is the English language appropriate and understandable?

*At this stage, reviewers can also suggest that a manuscript may be more appropriate for publication in another MDPI journal. To save the time and effort of reviewers, authors can request the transfer of review reports to another MDPI journal. The full list of journals published by MDPI can be found here.

Manuscripts submitted to MDPI journals should meet the highest standards of publication ethics:

  • Manuscripts should only report results that have not been submitted or published before, even in part.
  • Manuscripts must be original and should not reuse text from another source without appropriate citation.
  • The studies reported should have been carried out in accordance with widely accepted ethical research standards.

If a reviewer becomes aware of any scientific misconduct or fraud, plagiarism, or any other unethical behavior related to the manuscript, they should immediately raise these concerns with the in-house editor.

7.6. Overall Recommendation

Please provide an overall recommendation regarding the manuscript as follows:

  • Accept in Present Form: The manuscript can be accepted without any further changes.
  • Accept after Minor Revisions: In principle, the manuscript will be accepted after the authors revise based on the reviewers’ comments. Authors are given five days for minor revisions.
  • Reconsider after Major Revisions: The acceptance of the manuscript will depend on the revisions. The authors will need to provide a point-by-point response or rebuttal if some revisions regarding the reviewer’s comments cannot be made. A maximum of two rounds of major revisions per manuscript is normally permitted. The authors will be asked to resubmit the revised paper within ten days, and the revised version will be returned to the reviewers for further comments.
  • Reject: The manuscript has serious flaws or makes no original contribution and should be rejected with no offer of resubmission to the journal.

Note that recommendations are only visible to journal editors and not to authors. Decisions on revisions, acceptance, or rejection must always be well justified.

7.7. Guidelines for Reviewers for Registered Reports

The review process for registered reports is divided into two stages. In Stage 1, reviewers assess study proposals before data are collected. In Stage 2, reviewers consider the full studies, including their results and interpretation.

When reviewing Stage 1 papers, note that no experimental data or results will be included. Reviewers only need to assess the method, evaluating, for example, the following:

  1. The importance and soundness of the proposed hypotheses;
  2. The suitability and feasibility of the experimental and analytical methodology;
  3. Whether there are sufficient details given to replicate the proposed experimental procedures and analysis;
  4. Whether there are sufficient outcome-neutral tests of the hypotheses, including positive controls and quality checks.

Manuscripts that pass the Stage 1 peer review may be published immediately or after the successful completion of Stage 2 (at the authors’ discretion). Editorial decisions will not be based on the importance or novelty of the results.

For Stage 2 manuscripts, reviewers will be asked to appraise the following:

  1. Whether the data are adequate to test the proposed hypotheses through satisfying the approved outcome-neutral conditions (such as through quality checks and positive controls);
  2. Whether the stated hypotheses tested are the same as those in the approved Stage 1 submission;
  3. Whether the authors adhere precisely to the registered experimental procedures or are able to sufficiently justify any changes;
  4. Whether any new analyses (not mentioned in Stage 1) are methodologically sound and relevant;
  5. Whether the authors’ conclusions are justified given the data.

7.8. Guidelines for Reviewers for Depositing Review Activities into ORCID

MDPI allows reviewers to deposit their review activities into ORCID if the reviewers’ ORCID accounts are connected to their MDPI Submission System (SuSy) accounts. To do this, reviewers should register a SuSy account and connect their ORCID account to it here. Once the accounts are connected, reviewers can manually deposit their review records here. These records should then be visible on their ORCID profile.

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