Similarity Check

view simcheck factsheet

Read the factsheet in your language: español, العربية, Bahasa Indonesia, Brazilian Portuguese; or in English by clicking the image above.

For editorial originality, Similarity Check helps editors compare the text of submitted papers for similarity.

Similarity Check is a service for editors who want an extra check. The service helps our members to actively engage in efforts to prevent scholarly and professional plagiarism by providing their editorial teams with access to Turnitin’s powerful text comparison tool, iThenticate. Watch the video below to find out more:

Watch the introductory animation in your language: français; español; português do Brasil; 简体中文; 日本語; 한국어; العربية; Bahasa Indonesia; or English below.


With editors under increased pressure to assess higher volumes of manuscript submissions each year, Similarity Check provides immediate feedback regarding a manuscript’s similarity to other published academic and general web content. And as the iThenticate database contains over 50 million full-text scholarly content items, editors can be confident that Similarity Check will provide a comprehensive and reliable addition to their workflow.

As members contribute their own published content into iThenticate’s database of full-text literature, the service is open to any Crossref member who is actively publishing and assigning Crossref DOIs to their journal article content.


While there are several plagiarism screening tools available, Similarity Check participants enjoy cost-effective use of iThenticate because they contribute their own published content into Turnitin’s database of full-text literature. This means that as the number of participants grows, so too does the size of the database powering the service. More content in the database, means greater peace of mind for editors looking to determine a manuscript’s originality.

Turnitin also provides our members with access to additional features in iThenticate, such as enhanced text-matches within the document viewer. And with access to Turnitin’s dedicated Similarity Check support team, our members always have a direct line to Turnitin in order to discuss any technical or billing queries.

How it works

In return for a reduced fee for access to iThenticate, Similarity Check members allow Turnitin to index their full catalogue of current and archival published content as this ensures the highest level of text-matching accuracy. This means that the service is only available to members who are actively publishing DOI-assigned content.

Turnitin index members’ content directly via their Content Intake System. Their CIS accesses our metadata daily to collect the full-text content links provided by our members within their DOI deposit metadata. Turnitin follow these URLs and index the content found at each location. If full-text content is protected by authentication, then the member’s hosting provider must whitelist Turnitin’s IP range to ensure their content is accessible for indexing purposes.

On application to join, members must ensure they have full-text URLs present in the metadata of at least 90% of their registered articles (across all the member’s journal prefixes, as applicable). These URLs need to point directly to the full-text PDF, HTML or plain text content. Members must also ensure that these links are included in all future deposits too.

Once members meet the eligibility criteria for Similarity Check, Turnitin will provide them with access to iThenticate. Using iThenticate, members will be able to upload their own manuscripts to compare against the full corpus of published academic and general web content in Turnitin’s database. iThenticate provides a similarity score and a highlighted set of matches to similar text. Editors can then further review matches in order to make their own decision regarding a manuscript’s originality.

How to participate

If you’re a Crossref member and are assigning article-level DOIs which include the URL to the full-text PDF, HTML or plain text content for Similarity Check, then you’re eligible to join the service.

Your first step is to check that you have in fact included full-text URLs for Similarity Check in at least 90% of your Crossref article-level DOI deposits. You can check this using the widget below - just type your account name in the box below, select the correct one from the list, and your result will be automatically calculated.

If you do meet the obligations, the widget will link you to a form to apply for Similarity Check. If you don’t meet the obligations, the widget will allow you to download a CSV showing all your DOIs that don’t have the links, and instructions for how to add them.

Member Name
Member ID

Good news - you’re eligible to register for our Similarity Check service.
There are some exciting changes coming to the Similarity Check service, which means a few changes to the application form. You’ll be able to complete the new application form from early June. Let us know if you’d like us to drop you an email when the form is available.

We’re sorry, but you are not eligible to register for our Similarity Check service just yet.
To be eligible you need to register full-text urls for Similarity Check pointing to the full text article for more than 90% of your content. You can find out how to add these full-text urls for Similarity Check to your existing content here. To see exactly which content items are missing the full text article, simply click the “Generate CSV” button above. Please note, this CSV can only show the first 10k content items. If you have more than 10k content items missing DOIs, please contact us on

It looks as though you haven’t deposited any content with us yet. To be eligible for Similarity Check you need to be registering content with us and including urls for Similarity Check that point to the full text article for at least 90% of your content. You can find out more about how to register content here and more about the full-text urls for Similarity Check here. If you aren’t registering journal articles and instead are registering other content types (for example, conference papers) please get in touch with our membership team.

Obligations and fees


Similarity Check fees are in two parts: a per-document checking fee and an annual administrative fee. Per-document checking fees are paid directly to Turnitin and are significantly less than those charged by Turnitin to stand-alone iThenticate users. Additionally, volume discounts also apply. The annual administrative fee is paid to us and is set at 20% of your Crossref annual membership fee.


Do I need to be a Crossref member to join Similarity Check? Similarity Check is only available to Crossref members.

What technology are you using to provide this service? We have partnered with leading plagiarism screening systems vendor Turnitin to create the Similarity Check database and to use their iThenticate tool for checking documents against the database. As a Similarity Check member, you will need to sign a service agreement with Turnitin to use their system and to provide them with access to your full-text content. This agreement has been fully reviewed and approved by us and several of our members and should not require any additional negotiation.

What is the difference between Similarity Check and iThenticate? Similarity Check is a service specifically for our members. It provides members with cost-effective access to the iThenticate text comparison software from Turnitin. Other organizations and individuals can use the iThenticate service directly by contacting iThenticate.

Similarity Check members benefit from a tailored iThenticate experience that includes read-only access to the full text of articles in the Similarity Check database for comparison purposes, discounted checking fees and unlimited user accounts per organization.

I’m not able to include full-text URLs in my metadata. Can Turnitin index my content using another method? No. To ensure the most robust, secure and complete indexing of content, Turnitin is only able to support the direct-indexing method. This involves following the URLs that member’s provide in their Crossref metadata to find and index full-text content. Turnitin do also operate a general web crawler, called Walker, but this crawler targets general web content and is not suitable for comprehensively indexing full-text, published academic content.

To see which Crossref members are registering full text Similarity Check URLs visit Participation Reports (beta). These reports give a clear picture for anyone to see the metadata Crossref has including full text Similarity Check URLs used by Turnitin to index full text content. This is data that’s long been available via our Public REST API, now visualized.

Please contact our membership team with any questions or to get set up, or contact our support team for any technical or troubleshooting questions.

For iThenticate user help, please refer to Turnitin’s Similarity Check User Manual or get in touch with their support team at

Last Updated: 2019 May 23 by Christine Buske