supadetect vs Turnitin
Turnitin is the detector your university may run on your submission. You usually cannot run it yourself. supadetect is an independent detector that anyone can use before submitting. They are different tools with different models, so we cannot predict what Turnitin will say, and neither can anyone else.
| supadetect | Turnitin | |
|---|---|---|
| Who can use it | Anyone, with or without an account. | Sold to schools and universities; no plan for individuals. (Turnitin, checked 2026-11-10) |
| Paid price | Pro €18.99 a month or €119.88 a year, for 300,000 words a month. | Institutional licence; a 2025 report put the AI add-on at about $3.05–3.57 per student per year in California. (The Markup, checked 2025-06-26) |
| Spanish | Separate thresholds for Spanish and English, measured on texts in each language; Spanish interface. | Separate Spanish model since 12 September 2024. (Turnitin guides, checked 2026-11-11) |
| Length rules | At least 80 words; no upper score is hidden. | Needs at least 300 words; scores between 1% and 19% are shown only as an asterisk. (Turnitin guides, checked 2026-11-11) |
| What it publishes about accuracy | Thresholds and error rates per language with confidence intervals, from a test set never used for tuning (below). | States a false-positive rate under 1% for documents with 20% or more AI writing (English). (Turnitin, checked 2026-11-11) |
Facts about other products come from their own pages or from the reports linked, on the date shown. Prices and features change; check the source before deciding.
When each makes sense
- Turnitin is chosen by your institution and combines AI detection with plagiarism matching against its database.
- supadetect is for an independent read before you submit, or for a teacher who wants a second opinion with the evidence highlighted. We don't keep your text, and our error rates per language are public.
Our guide (in Spanish) on whether Turnitin detects ChatGPT explains how its scores are shown.
Our measured numbers
Rendered from the measurement file of Engine 2026.11-oculus-v0. We do not measure other vendors' detectors, so there are no competitor accuracy figures on this page.
| English human texts called Likely AI | 1.2 % (0.9–1.7) |
| English AI texts called Likely AI | 89.2 % (87.1–91.0) |
| Spanish human texts called Likely AI | 1.4 % (1.0–2.0) |
| Spanish AI texts called Likely AI | 99.5 % (98.8–99.8) |
What independent studies found about detectors in general
- Seven detectors flagged 61% of 91 human TOEFL essays written by non-native English speakers as AI-written (Liang et al., 2023). (Patterns / arXiv, checked 2026-11-11)
- A test of 14 detection tools found them "neither accurate nor reliable", and easy to fool with paraphrasing (Weber-Wulff et al., 2023). (International Journal for Educational Integrity, checked 2026-11-11)
- An audit by the University of Chicago's Becker Friedman Institute found large differences between commercial detectors, with only one meeting a 0.5% false-positive cap (Jabarian & Imas). (Becker Friedman Institute, checked 2026-11-10)