iThenticate vs Turnitin: the similarity check journals run

What is iThenticate, and what is Crossref Similarity Check?

iThenticate is a similarity checker made by Turnitin for manuscripts, grant proposals and other research writing. It compares a document with a large database of published and web content and produces a report of matching text, much like the Turnitin report you may know from your university.

Crossref Similarity Check is how most journals get iThenticate. Crossref is the organisation that registers DOIs for scholarly publishers. Its Similarity Check service gives member publishers access to iThenticate at a member rate, on one condition that explains why the database is so strong: publishers who join must let Turnitin index their own published full text. Crossref says the resulting database holds over 78 million full-text scholarly content items, plus academic and general web content.

So when a journal’s submission system says your manuscript is being “checked for similarity”, it is very likely running iThenticate through Similarity Check. Elsevier, for example, says that all new submissions to many of its journals are screened this way automatically inside the editorial system.

iThenticate vs Turnitin: the differences

The underlying matching technology comes from the same company, and the reports look alike. The differences are in who uses each product and on what:

The most useful practical point is the content. Because Crossref members feed their full text into the database, iThenticate is particularly good at finding overlap with published journal articles, including subscription articles that a free checker can’t see. A manuscript that looks fine on a university Turnitin check can still show matches on iThenticate, and the reverse happens too. For what each part of a Turnitin report means, see our guide to reading a Turnitin report; the iThenticate report is organised in much the same way.

What the editor sees in an iThenticate report, and what they do with it

The editor sees an overall similarity score, a list of matched sources and your manuscript with the matching passages highlighted. Crossref explains that the score is the number of matching words divided by the total number of words, after any exclusions.

Before reading it closely, editors can exclude quoted material, the bibliography, the methods section, preprints, small matches and specific sources. Each exclusion recalculates the score, which is why the figure an editor acts on can be quite different from the first number the system shows.

Then comes judgement. Crossref tells its members that iThenticate checks for similarity, not plagiarism, and that editors and reviewers should decide whether each match is acceptable rather than rejecting on a threshold. Elsevier’s guidance to its editors makes the same point: a high score doesn’t necessarily mean plagiarised text, and interpreting the report needs subject knowledge. In practice editors look at:

• Where the matches are. Overlap in the methods section or in standard phrasing worries an editor far less than a matched paragraph in the results or discussion.
• Whether one source dominates. A large share from a single paper suggests copying or duplicate publication; small shares from many sources usually reflect common phrasing.
• Whether the source is your own work. Your thesis, a preprint or a conference paper often shows up, and the editor needs to know whether you have disclosed it.
• Whether matched text is cited and quoted. A properly quoted, cited passage is not a problem even when it is highlighted.

Is there a percentage journals accept?

There is no universal cut-off. Some journals publish their own guidance and many editors have a figure in mind, but the same score can mean 30% from one paper or 1% from each of thirty, as Elsevier points out, and those are very different cases. What gets a paper returned or desk-rejected is a pattern of matches that needs explaining. Our guide to why papers get desk-rejected covers the other common reasons.

Will my own thesis or preprint show up as a match?

Often, yes. If your thesis is on Shodhganga or a university repository, if you posted a preprint, or if part of the work appeared in conference proceedings, iThenticate may find it and highlight the overlapping text. Publishers using iThenticate 2.0 can also keep a private repository of manuscripts submitted to their own account, so a paper sent to one of their journals earlier can match a later submission to another.

This is normal and usually harmless, as long as the editor already knows. Three habits prevent problems:

1. Disclose earlier versions in the cover letter. Say that the paper draws on your PhD thesis, give its title and where it is available, and name any preprint or conference version. Our cover letter guide shows where this goes, and the free cover letter generator drafts the rest of the letter, so you can add the disclosure to its draft.
2. Follow the journal’s preprint policy. Many journals accept papers that were posted as preprints, but not all do. Check before you post, not after.
3. Rewrite rather than paste from your thesis. A journal article is shorter and differently structured, and rewriting it properly also reduces the overlap an editor has to judge.

What is not harmless is sending the same manuscript to two journals at once. A private repository exists partly to catch exactly that.

Can authors check a manuscript on iThenticate before submitting?

There are three reliable routes:

• Your institution. Some universities and research institutes hold iThenticate for their researchers, often through the library or research office. Ask before you pay for anything.
• Your university’s own checker. A Turnitin or DrillBit check through your university is not the same database, but it catches most copied or poorly paraphrased passages. In India, the DrillBit check under ShodhShuddhi is available to PhD scholars and faculty at member universities.
• Paid individual credits. Turnitin sells iThenticate credits to individual researchers, priced per manuscript and valid for a year. Check the current plans on ithenticate.com. Turnitin’s page says the individual plans don’t include AI-writing detection.

Avoid anyone offering to run your paper through “their” iThenticate or Turnitin account for a fee. You would be handing an unpublished manuscript to a stranger, and an account used that way may store your paper in a repository where it later matches your own submission.

If the check shows real problems, the fix is the writing: rewrite in your own words, quote and cite properly (see our paraphrasing and quoting guide), and cut text carried over from the thesis. Our similarity reduction support helps with that revision.