Crossref Similarity Check

Web · API· paid plans from $3.33/mo

Freedom report

Two barsScore 6.4

Free tierA free tier is on its own pricing page
Runs widely1 of 6 device platforms
DocumentedPlans, terms and facts published

Crossref Similarity Check is ranked #5 of 31 in plagiarism checkers on Freedom251. It runs on API, Web. Paid plans start at $3.33/mo.

Crossref Similarity Check plans and pricing

All plans

Similarity Check per-document checking Free Invoiced annually in January for the previous year’s usage. First 100 documents per year free · up to 25,000 words per document · subsequent rates are $0.75, $0.65, $0.55, $0.45, $0.30, or $0.25 per document by annual volume tier crossref.org · 9 Oct 2026

Similarity Check annual service fee $40/yr Included in the annual membership fee invoice; prorated for the remainder of the calendar year when first joining. 20% of annual Crossref membership fee · fee depends on membership tier crossref.org · 9 Oct 2026

Compared on plagiarism checkers

Free plan: No
Web source matching: Yes
Academic source matching: Yes
Report export formats: PDF
API access: Yes

Best Crossref Similarity Check alternatives

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The record

Purpose: Similarity Check helps Crossref members detect potential plagiarism by comparing manuscripts with published academic and general web content.
Powered by: The service is powered by iThenticate text comparison software from Turnitin.
Similarity reports: iThenticate reports a Similarity Score and highlights matching text for editors to review.
Database: Crossref says the iThenticate database contains over 78 million full-text scholarly content items.
Access methods: Users can submit manuscripts through the iThenticate tool or through a manuscript submission system using an API.
Member features: Similarity Check members receive read-only access to full text in the comparison database, discounted checking fees, unlimited organizational user accounts, and enhanced text matches in Document Viewer.
Eligibility: Participation requires Crossref membership, actively publishing DOI-assigned content, and including full-text URLs in metadata for Similarity Check.
Indexing: Turnitin’s Content Intake System accesses Crossref metadata daily to collect members’ full-text URLs and index the linked content.
Workflow: Editors can upload a manuscript and receive an immediate report showing potential matches and how the paper overlaps with other work.
Fee structure: The service charges an annual fee equal to 20% of the Crossref membership fee plus per-document checking fees, with volume discounts.
Word limit: The published per-document price schedule applies to documents up to 25,000 words.
Service status: Crossref directs users to Turnitin’s service status page for real-time updates about performance and ongoing issues.
Regional availability: Crossref states that it can no longer offer Similarity Check to members based in Russia.
Provider: Crossref describes itself as a not-for-profit membership organisation that began in January 2000.
Price from: $3.33/mo

Where it ranks on Freedom251

Best Plagiarism Checkers in 2026#5 of 31

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Sources

crossref.org/documentation/similarity-check· checked 9 Oct 2026
crossref.org/fees/· checked 9 Oct 2026
crossref.org/about/· checked 9 Oct 2026