Turnitin and iThenticate check against the same databases, but these services are designed for different categories of users. While Turnitin is designed to meet the needs of instructors and their courses, iThenticate is a plagiarism detection service available to faculty, staff, and graduate students. iThenticate cannot be used for coursework.
Turnitin is a 'text-matching' software which is designed to educate students regarding appropriate citation and referencing techniques. Turnitin is also used to provide confidence in the academic integrity of students' work. Turnitin does this by comparing a student submission against an archive of Internet documents, Internet data, a repository of previously submitted papers, and subscription repository of periodicals, journals, and publications. Turnitin then creates an 'Originality Report' which can be viewed by both instructors and students, which identifies where the text within a student submission has matched another source.
It is important to note that Turnitin does not detect plagiarism. Turnitin will only match the text within a student's assignment to text located elsewhere (e.g. found on the Internet, within journals or on databases of student papers). Correct interpretation of these results by both lecturers and students is essential for the successful use of Turnitin.
iThenticate is plagiarism detection software that is designed to be used by researchers and writers to ensure the originality of written work before publication. Faculty, staff and graduate students can check their articles and book chapters to be submitted for publication, grant proposals, theses and dissertations. The iThenticate plagiarism tool is provided by iParadigm, the parent company to Turnitin.
More resources:
TurnItIn Student Quick Start Guide