Similarity Check

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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, it’s important to find a fast, cost-effective solution that can fit seamlessly into your submission workflows. Similarity Check allows editors to upload a paper, and receive a report giving 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 the Similarity Check service works

In return for a reduced fee for access to iThenticate, Similarity Check subscribers 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 and including full-text URLs in their metadata which Turnitin can access.

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.

On application to join the service, 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.

Please note that the metadata which members deposit with Crossref is available to be searched and retrieved by everyone, and this includes Similarity Check URLs. If your content is paywalled, please make sure that your Similarity Check URLs prompt an authentication step before allowing a user to access full-text content. You’ll need to ensure that your hosting provider has whitelisted Turnitin’s IP range to ensure the content is accessible for Turnitin to index.

Once members meet the eligibility criteria for Similarity Check, members will be provided 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 have full-text URLs for Similarity Check in the metadata for at least 90% of your content, then you’re eligible to join the service.

If you aren’t yet a member of Crossref, then you can apply to join here. You can find more information on how to include these full-text URLs in your new registrations or add them to content that you’ve previously registered on our support site.

Journal publishers - we’ve created a tool that you can use to check whether you’re eligible to join the service. Just start typing your account name in the box below and the tool will suggest account names that match. Select the correct one from the list, and your result will be automatically calculated. Don’t worry, you don’t need to know your Member ID.

If you do meet the obligations, the widget will link you to a form where you can apply for Similarity Check and click to accept the service terms. If you don’t meet the obligations, the widget will provide a CSV to download which shows all your DOIs that don’t have the links. It will also provide instructions for how to add the missing full-text URLs.

If you don’t publish any journals and exclusively publish other content types (for example, conference proceedings or books) then the tool may not give accurate results. If this is the case, do contact our membership specialist and they’ll be able to help you work out if you’re eligible for the service.

Member Name
Member ID
Good news - you’re eligible to register for our Similarity Check service.

You can now apply here and accept the service terms.

Once we receive your application, we’ll work with the team at Turnitin to confirm that they can access your content. We’ll also send you a pro-rated invoice for your first year subscription to the service. Don’t forget, if your full-text content is protected by authentication, then you’ll need to ask your hosting provider to whitelist Turnitin’s IP range to ensure your content is accessible for indexing purposes. Do make sure that this is done before you apply.

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 and we'll be able to provide you with the full list.
We’re sorry, but you are not eligible to register for our Similarity Check service just yet.
It looks as though you haven’t registered 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.
Please note - if you aren't registering ANY journal articles at all and are only registering non-journal content (eg conference papers, books) then the tool may not give accurate results. Please get in touch with our membership team for more help.


Similarity Check fees are in two parts: an annual service fee plus a per-document checking fee.

The annual service fee is 20% of your Crossref annual membership fee and is included in the renewal invoices you receive each January. When you first join Similarity Check, you’ll receive a one-off pro-rated invoice for the remainder of that calendar year.

Per-document checking fees are also billed in January on a separate invoice. Volume discounts apply, and your first 100 documents are free of charge!


Do I need to be a Crossref member to join Similarity Check? Yes, 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.

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, but only 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.

What do I do if I have questions or issues with iThenticate?

If you have a technical issue with iThenticate (ie a bug or error message), please contact the team at Turnitin on

Phone: 1 866 816 5046 x241

If you have a question about how to actually use iThenticate, please contact our Similarity Check specialist.

How do I find out about outages or planned maintenance that affect the iThenticate system?

You can check the current health of the application at any time on the Turnitin status page. It will display information on service outages, maintenance alerts, or incidents related to the performance of iThenticate. You can also subscribe to the notifications feed to automatically receive notices.

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.

Please contact our membership specialist with any questions or to get set up, or contact Turnitin 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 31 by Amanda Bartell