Similarity Report Matches My Own Preprint: What Now?

A similarity report can match a journal manuscript to its author's own public preprint without establishing plagiarism. Verify that the matched source really is your preprint, record its version and link, and check the journal's rules. Review unrelated matches separately instead of rewriting legitimate overlap just to lower a score.

By plagiarism-checker-online.net Editorial Team | Published October 9, 2026

You posted a draft on a preprint server in the spring. Now the journal manuscript is ready, you run a similarity check before submitting, and the top match is your own preprint at a very high percentage. For a grad student whose corresponding author won't answer email until Monday, that's an alarming screen. Don't touch the manuscript yet. A match like this is a question about source identity and disclosure, not a verdict.

Why a preprint match is not a plagiarism verdict

Crossref runs the Similarity Check service, which gives its member publishers access to iThenticate. Its documentation on understanding your Similarity Report (page last updated in May 2020, reread October 9, 2026) makes three points that matter here. The tool measures similarity rather than deciding plagiarism. Authors who already shared a manuscript as a preprint should expect a high overlap with it. And editors shouldn't set a score above which they reject manuscripts automatically, because a person has to judge whether a match is acceptable.

The same page explains the arithmetic. The score is the number of matching words divided by the document's total word count, and applying an exclusion recalculates it. A manuscript that is mostly your posted draft will produce a large number by arithmetic alone. The percentage can't know whose preprint it is.

These statements describe one service and its customers. Your journal may use another tool or write its own rules. The ICMJE recommendations on overlapping publications, written for medical journals, say authors should tell a journal when work was posted on a preprint server and provide the link. Treat Crossref and ICMJE as examples of how editors reason, not as a universal rulebook. If you want the broader reading skills first, our guide to reading a plagiarism report covers match types in general.

Identify the exact matched source

Open the matched source in the report and answer the questions below before you decide anything else. Each answer goes into the evidence log later in this article.

Authors, title, DOI and version

• Authors: Are the names and order the same as on your submission?
• Title and text: Is the title identical, and which sections of the manuscript does the match cover?
• DOI or URL: Does it resolve to the preprint record you posted, with the posting date earlier than your submission?
• Version: If you posted v1 and v2, which one matched? Compare it with your own upload history.

The version question has a second layer. The ICMJE text advises authors not to post the published article, or interim versions revised after journal feedback, to the preprint server. If the matched version is one you posted after review began, ask the editor about it directly. That's a journal-policy question, not a similarity question.

Mirror pages and coauthor changes need explanation

Preprints get copied. An institutional repository, a search index or an aggregator may hold a copy, and the report may list that copy instead of the original record. Crossref also notes that some preprints sit in its Posted Content repository, and that iThenticate crawls preprint repositories on the web as well. So a preprint can appear even when an administrator excluded Crossref Posted Content. Find the original record and note both addresses.

A different author list is the case Crossref tells editors to investigate. There can be ordinary reasons: a collaborator left the project, a new coauthor joined during revision, or a name changed. Confirm the change with every author, and be ready to explain it. Don't leave it for the editor to discover.

Own preprint, someone else's preprint or published article?

Four cases with an action and the evidence to keep

The matrix below is our own teaching tool, not a standard from Crossref or any journal. Find the row that matches what the report shows, then take the action and save the evidence.

Cases A and C usually end with disclosure rather than rewriting. Cases B and D need a conversation before the manuscript goes anywhere. If a match fits none of the rows, it isn't a preprint question. Review it like any other match, using the steps in our plagiarism checking guide.

Build an overlap evidence log before journal submission

Source URL, passage, relationship, action, policy link

One row per matched source is enough. The log protects you in two ways. It makes your disclosure specific, and it keeps the preprint from hiding other matches that need real attention. The sample below is invented teaching data for a fictional manuscript. The addresses use reserved example domains and none of them describes a real paper.

Notice the third row. It's the one the percentage hides. Your preprint can account for most of the score while a small, real problem sits in a paragraph nobody looked at. Work through every row, not just the biggest one. Add a column for the date you checked each link, because pages change.

Tell the editor without hiding other matches

Springer Nature's support article on preprints and similarity checks (modified April 2024) recommends declaring a registered preprint in the cover letter and giving its link before the check runs. It adds that a reply clarifying the match can help if the journal notifies you. That advice comes from one publisher's support pages. The ICMJE text is similar in spirit: inform the journal, provide the link, and consider saying in the manuscript that a preprint exists.

A short clarification example, not a legal guarantee

Here's an original sample with placeholders. Adapt it to the journal's instructions and your facts.

A preprint of this manuscript was posted on [server name] on [date] and is available at [DOI or URL]. The author list and order are the same as in this submission. The submitted version differs from the preprint in [list the main changes]. We expect the journal's similarity report to show substantial overlap with that preprint. We reviewed the other matches in our own check and cited or revised them where needed. Please let us know if the journal would like the preprint handled in any particular way.

Only write the sentence about other matches if you've actually reviewed them. The note covers the preprint. It doesn't excuse overlap with anyone else's work, and it can't promise how an editor will respond. Nothing here is legal advice.

What an optional scan can and cannot establish

A separate text comparison can be useful when you want to see what a public-web check finds before the journal's does. It can also surface a small match you missed, like the blog row above. Know its limits first. PCO's scans use PlagAware, and PlagAware's FAQ says its default search covers publicly available sources, so paywalled journals and course books aren't covered, and sites that block automated reading are skipped. Your public preprint may well appear. A publisher's tool has its own repositories, settings and exclusions, so a scan here can't reproduce that report. Our pre-submission scan walkthrough explains how to treat a self-check as a private review step.

If a check would help, the plagiarism checker charges $0.29 per standard page, where one page is 1,800 characters including spaces, with a $0.90 minimum and no subscription. Results usually arrive within about 15 minutes. The pricing page shows the current rates, and the order step displays the page count and price before you pay. Read the privacy policy before uploading, and don't send an unpublished manuscript if your coauthors, funder or journal require confidentiality. When you're ready, you can start a plagiarism check. A clean result won't clear journal policy, prove novelty or confirm that your coauthors agree.

Final submission checklist

1. Open every matched source in the report and classify it as case A, B, C or D.
2. Confirm the preprint's authors, title, DOI, version and posting date against your own records.
3. Resolve any author-list difference with every author before you submit.
4. Read the journal's current instructions on preprints, prior publication and cover letters. Save the page.
5. Check the publication agreement or posting terms if a published or revised version appears.
6. Complete the evidence log, including unrelated matches and the date you checked each link.
7. Add the preprint link to the cover letter and, if the journal wants it, to the manuscript.
8. Rewrite or cite only the matches that need it, and leave legitimate preprint overlap alone.
9. Keep your clarification note, the log and the journal policy in one folder in case an editor asks.

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