Direct answer
Grammarly does not include a full plagiarism check on its free plan: the plagiarism checker is a Premium feature, and free accounts only get a very small number of trial runs before the tool is gated behind an upgrade prompt [1]. Even when it runs, Grammarly checks your text against the licensed databases it indexes, not against the institutional Turnitin repository that your university actually uses [2]. That distinction matters because a clean Grammarly result does not guarantee a low similarity score or a low AI writing score in your course's Turnitin submission.
Does Grammarly's Free Plan Actually Include A Plagiarism Checker?
Grammarly's plagiarism checker is marketed as part of Grammarly Premium, and the free tier is best understood as a preview rather than a working originality tool. Free users can occasionally trigger a limited number of checks, but the feature is deliberately capped so that sustained use requires a paid upgrade [2]. In practice, a student who needs to verify a full 3,000-word essay cannot rely on the free plan to do it repeatedly.
The technical coverage is also narrower than most students assume. Grammarly compares your text against the web pages, academic papers, and periodicals available through its licensed content partners, which is a large index but is not the same corpus your university's Turnitin instance searches [1]. A passage can be flagged by Turnitin because it matches a previously submitted student paper that Grammarly simply does not have access to.
There is a second gap that catches students off guard: similarity checking and AI detection are different signals. Grammarly's plagiarism checker looks for matching text, while Turnitin's AI writing indicator estimates whether text was likely generated by a large language model [2]. Passing one does not mean you pass the other, and a free Grammarly run tells you nothing about your AI score.
What Are The Limits Of Grammarly's Plagiarism Checker Compared With A Turnitin Similarity Report?
A Turnitin Similarity Report compares your submission against three source categories at once: the student paper repository, internet sources, and publications, then returns an overall percentage with a match-by-match breakdown [3]. That repository layer is the crucial difference, because it is where institutional submissions live and where a lot of accidental overlap between classmates' work is detected. Grammarly has no equivalent to that repository.
Turnitin also reports the way your instructor will actually see the document. The report highlights matched passages in context, links each match to its source, and can exclude quoted or bibliographic material so the percentage reflects genuine overlap rather than properly cited quotes [3]. Because it is the same report type rendered in the instructor's LMS, it is a direct preview of the verdict rather than a proxy for it.
One detail worth knowing before you panic about a number: when Turnitin's AI detection confidence falls below its 20% threshold, the report displays *% instead of an exact percentage, signalling a low-confidence AI signal rather than a confirmed one [3]. Grammarly does not present an equivalent confidence band, so students comparing the two tools are often comparing a precise-looking number with a differently calibrated one. Neither number is interchangeable with the other.
How Can Students Verify Originality With A Real Turnitin-Style Report Before Submitting?
The most reliable pre-submission workflow is a non-repository check: you run your draft through a checking service that does not add the file to Turnitin's student paper database, so your own work does not become a future match for anyone else [4]. This gives you the same report types your instructor will see while keeping your draft out of the institutional corpus.
Reading the report before you submit is what converts the check into an actual improvement. Students who review flagged passages, rephrase genuine overlap, and re-run the check catch problems while there is still time to fix them, instead of discovering them after the deadline [4]. Because the check is non-repository, you can iterate as many times as your draft needs without polluting the database.
For students in the UK, US, Canada, Australia, New Zealand, and Ireland, this approach also resolves the free-tool dead end. A free checker gives you a partial signal; a real report gives you the score, the flags, and the similarity summary your professor will see, so you can decide what to revise rather than guessing [4]. That is the difference between hoping a draft is clean and knowing it.
If you have already hit Grammarly's free-run ceiling and still do not know what your instructor's report will say, turnitin0 closes that gap: upload your draft and get the actual Turnitin AI and similarity reports back in minutes, without your file entering the student paper database.
※ Turnitin0.com - Actual Turnitin AI Report Cover, Score, Flag And Similarity Summary
FAQ
Is Grammarly's plagiarism checker really free?
No, not in any practical sense. The checker is a Premium feature, and the free plan only allows a small number of trial runs before you are prompted to upgrade [1]. For a full essay you should not count on the free tier.
Can Grammarly detect AI-generated text the way Turnitin does?
Grammarly's plagiarism checker looks for matching text, not for AI authorship signals, so it is not a substitute for Turnitin's AI writing indicator [2]. Turnitin also shows *% instead of a precise figure when AI confidence is below its 20% threshold [3].
Why did my draft pass Grammarly but still get flagged by Turnitin?
Because Turnitin searches the student paper repository, internet sources, and publications, while Grammarly only searches its licensed index [3]. Overlap with a previously submitted classmate's paper will show up in Turnitin and never appear in Grammarly.
Can I check my draft without it being stored in the student paper database?
Yes. A non-repository check lets you preview the report without adding your file to Turnitin's student paper database or sharing it with third-party databases, so you can revise and re-run freely [4].