iThenticate vs Turnitin: the similarity check journals run

What is iThenticate, and what is Crossref Similarity Check?

iThenticate is Turnitin’s checker for manuscripts, grant proposals and other research writing. It takes your document and compares it with a big database of published content and web content. What comes out is a report of the matching text. It looks a lot like the Turnitin report you have seen at your university.

Most journals get iThenticate through Crossref Similarity Check. Crossref is the body which registers DOIs for scholarly publishers. Under Similarity Check, member publishers get iThenticate at a member rate. But there is one condition, and it is the reason the database is so strong. A publisher who joins has to let Turnitin index its own published full text. As per Crossref, the database built this way holds over 78 million full-text scholarly content items, and academic and general web content on top of that.

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

iThenticate vs Turnitin: the differences

Both use matching technology from the same company, and the two reports look alike. Where they differ is in who uses each product, and on which kind of writing.

For a scholar the most practical difference is the content. Crossref members put their full text into the database, so iThenticate is very good at catching overlap with published journal articles. That includes subscription articles which a free checker can’t see. A manuscript can pass the university Turnitin check and still show matches on iThenticate. The opposite also happen. Our guide to reading a Turnitin report explains each part of it, and the iThenticate report is laid out in almost the same way.

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

In the report the editor gets an overall similarity score and a list of the matched sources. Below it is your manuscript with every matching passage coloured. Crossref explains the score as the number of matching words divided by total number of words, after any exclusions.

Before reading closely, the editor can remove some material from the count. This can be quoted text, the bibliography, the methods section, preprints, small matches or specific sources. With every exclusion the score is worked out again. Because of this, the figure an editor finally acts on can be quite far from the first number the system showed.

After that it comes down to the editor’s judgement. Crossref tells its members that iThenticate checks similarity and does not check plagiarism. It says editors and reviewers should decide if each match is acceptable, and should not reject on a threshold. Elsevier’s guidance to its own editors says the same thing. A high score does not always mean the text is plagiarised, and you need subject knowledge to read the report properly. In practice editors mostly check the following.

• Where the matches are. If the overlap is in the methods section or in standard phrases, the editor is much less worried. A matched paragraph in the results or discussion gets far more attention.
• Whether one source dominates. Most of the matching from one single paper makes the editor suspect copying or duplicate publication. Small shares from many sources are mostly just common phrasing.
• Whether the source is your own work. Many times your thesis, a preprint or a conference paper shows up in the list. The editor needs to know if you have disclosed it.
• Whether matched text is cited and quoted. The report highlights quoted passages also, but with quote marks and citation nobody minds them.

Is there a percentage journals accept?

No universal cut-off is there. Some journals publish their own guidance, and many editors have some figure in mind. But Elsevier points out that one score can mean 30% from one paper or 1% from each of thirty, and those two cases are very different. What gets a paper returned or desk-rejected is a pattern in the matches that the editor wants you to explain. For the other common reasons, read our guide on why papers get desk-rejected.

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

Many times, yes. If your thesis is on Shodhganga or in a university repository, iThenticate may find it and highlight the text that overlaps. Same with a preprint you posted, or a part of the work that came out in conference proceedings. Publishers on iThenticate 2.0 can also keep a private repository of manuscripts sent to their own account. So a paper you sent to one of their journals earlier can match when you submit later to another one of theirs.

This is normal, and mostly harmless, as long as the editor knows about it. Keep these three habits and you will be safe.

1. Disclose earlier versions in the cover letter. Mention that the paper draws on your PhD thesis, with the thesis title and where people can find it. Name the preprint or conference version too, if there is one. Our cover letter guide shows where to put this. The free cover letter generator will draft the rest of the letter, and you can add the disclosure into that draft.
2. Follow the journal’s preprint policy. Many journals take papers that were already posted as preprints. Some journals don’t accept them, so read that journal’s policy first and post the preprint after that only.
3. Rewrite rather than paste from your thesis. A journal article is shorter and it is built in a different way. When you rewrite it properly, the overlap the editor has to judge also comes down.

But sending same manuscript to two journals at the same time is not harmless. The private repository is there partly to catch exactly this.

Can authors check a manuscript on iThenticate before submitting?

Yes, and you have three reliable options for it.

• Your institution. Some universities and research institutes have iThenticate for their researchers, and mostly the library or research office runs it. Ask them first, before you pay for anything.
• Your university’s own checker. Turnitin or DrillBit through your university does not use the same database. Still it will catch most of the copied passages and the poorly paraphrased ones. In India, PhD scholars and faculty at member universities can use the DrillBit check under ShodhShuddhi.
• Paid individual credits. Individual researchers can buy iThenticate credits from Turnitin. The price is per manuscript and the credits are valid for one year. See ithenticate.com for the current plans. As per Turnitin’s page, the individual plans don’t include AI-writing detection.

Don’t go to anyone who offers to run your paper through “their” iThenticate or Turnitin account for a fee. That way your unpublished manuscript goes to a stranger. Also, an account used like this may store the paper in a repository, and later it can match against your own submission.

If the check shows real problems, what you have to fix is the writing. Put it in your own words, and quote and cite properly (our paraphrasing and quoting guide helps here). Remove the text carried over from the thesis. Our similarity report review can guide you through that revision.