Comparison guide

AI detection & plagiarism tools compared

Detection and originality checkers, with their documented accuracy limits and the false-positive risks that come with them.

Criterion	QuillBot	GPTZero	Originality.ai	CheckWise AI
Provider	QuillBot (Learneo)	—	—	CheckWise AI
What it is for	A suite of writing tools for paraphrasing, summarising, grammar checking and AI detection, popular with students.	An AI detection service that estimates whether a piece of text was written by a person, by an AI model, or by a mix of both.	An AI content detector and plagiarism checker aimed at publishers, agencies, writers and educators.	An independent document-analysis service that runs an AI-writing check and a similarity (plagiarism) check on the same upload.
Latest confirmed model	—	—	—	—
Main capabilities	Paraphraser (Depends on plan) Summarizer (Depends on plan) AI Detector (Depends on plan) Grammar checker Team plans	AI Detector that highlights passages it suspects are AI-generated and gives an overall estimate Classifies text as human, mixed or AI, with sentence-level highlights (via the API) Plagiarism Check and Advanced Scan on paid plans Writing Replay / authorship tool that shows how a document was written, including copy-and-paste activity Chrome extension and Google Docs add-on, plus integrations listed for Google Classroom, Canvas and Zapier	AI Checker with sentence highlights and shareable/PDF reports Plagiarism Checker and bulk scanning Fact and AI hallucination checker Readability and grammar/spelling checkers Chrome extension that scans in Google Docs and can replay the writing process	AI content analysis Similarity (plagiarism) check File upload or pasted text Downloadable reports Automatic data purge
Free plan	Yes Paraphraser 125 words per input; Summarizer 1,200 words; AI Detector 1,200 words per scan, 6 scans/day	Yes	Yes	No
Cheapest paid plan	Premium: $19.95/mo $8.33/mo billed annually Annual $99.95 billed yearly; monthly figure from QuillBot FAQ; regional pricing applies	Pricing not verified	Pricing not verified	No monthly list price
API access	No	Yes	Yes	No
Learning curve	Beginner-friendly	—	—	Beginner-friendly
Last verified	Oct 19, 2026	Oct 13, 2026	Oct 13, 2026	Oct 19, 2026

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How to choose

Treat every score as a signal, never as proof — false positives are documented.
Paraphrasing reduces detection rates in published studies.
Plagiarism checking and AI detection are different products.

The table shows up to five entries in the directory's editorial order, not a ranking. Every value links back to a record with sources and a last-verified date.