Scribbr AI Detector Review

Scribbr, best known for its plagiarism checker and citation generator for students, offers a free AI Detector at scribbr.com/ai-detector. You paste text (up to 1,200 words per submission, unlimited submissions, no sign-up) and it returns an AI score from 0% to 100% plus paragraph-level feedback. Rather than a single AI-or-human verdict, it labels each section as AI-generated, AI-generated and AI-refined, human-written and AI-refined, or human-written, so you can see where paraphrasing or editing tools may have been used. Scribbr says it detects text from tools such as ChatGPT, Gemini and Copilot, and that it analyses English, Spanish, German and French.

Scribbr is explicit that no detector is fully accurate and recommends scanning longer passages rather than single sentences or paragraphs. Its FAQ says the free detector catches GPT-2, GPT-3 and GPT-3.5 text with average accuracy, while the Premium AI Detector is more accurate and can detect GPT-4. The premium check is not sold on its own: it comes as part of Scribbr's paid plagiarism report. Scribbr says it does not store or share submitted text, and the detector does not check for plagiarism (that is a separate tool). The detector page also points users to QuillBot's AI Detector as an alternative.

The premium AI check is bundled into the premium plagiarism report ("from $19.95"), which Scribbr's comparison table lists as including a precise AI writing percentage; Scribbr's review article adds that the premium AI check has no word limit. The plagiarism page also says you can recheck flagged AI sections unlimited times. Prices are one-off per document, not a subscription. For a 7,499-word paper the cheapest tier works out to about $0.27 per 100 words ($19.95 / 75).

Prices checked on the vendor's pricing page on November 2, 2026. See the Scribbr AI Detector and Scribbr Plagiarism Checker pricing.

What Scribbr's own pages list:

It suits students who want to check their own essay before submitting it, and teachers or editors who want a quick, free second opinion on a short passage, especially when they want to see which paragraphs look AI-refined rather than fully generated. The 1,200-word cap means long papers must be checked in pieces, and Scribbr itself says the free detector is weaker on GPT-4-class text. No AI detector, this one included, should be treated as proof of misconduct.

For institution-wide checking built into a learning platform, schools generally use Turnitin. For a detector with document scanning, sentence highlighting and team plans, compare GPTZero or Originality.ai. QuillBot's free detector is the one Scribbr links to itself and Copyleaks adds an API for checking at scale.

Most published accuracy figures come from interested parties. Scribbr's own comparison of 12 detectors ranks its premium detector first at 84% accuracy and its free detector tied second at 78% with QuillBot, with no false positives; the detector page's FAQ quotes a different best-free figure of 68%. Competing vendors are less positive: Pangram (January 2026) found the free tool caught 4 of 9 AI samples, missing all 3 Claude texts, while correctly passing 3 of 3 human texts, and GPTZero calls its accuracy mixed and cites a ZDNet test in which it flagged human writing as AI. Treat a high score as a reason to look more closely, not as a verdict.