This document introduces Crossref Similarity Check, a service that allows publishers to screen manuscripts for plagiarism using Turnitin's text comparison tool, iThenticate. It notes over 1,700 Crossref members currently participate by contributing their published content to iThenticate's database. The service works by uploading documents to iThenticate to produce similarity reports for editors to check for legitimate similarity or require further investigation. It addresses common questions about how the service works, who uses it, and costs.