AI-generated writing is no longer an exception. It has become part of how essays, reports, articles, and research drafts are produced. Students use it to brainstorm. Professionals use it to speed up drafts. Editors use it to clean up language. The boundary between human writing and AI-assisted writing has blurred enough that telling the difference is no longer simple. This shift has made one name unavoidable in academic discussions: Turnitin. The Turnitin AI checker is now one of the most widely discussed AI detection systems used by universities to review student writing. For some students, Turnitin feels like an invisible judge scanning every submission. For instructors, it is positioned as a safeguard against plagiarism and, more recently, AI-generated writing. For institutions, it represents consistency and scale. But what does the Turnitin AI checker actually do? Does Turnitin detect AI reliably? Can it detect ChatGPT? How accurate is it, and what happens if your...