QuillBot AI Detector

An entry in the Humanizer Wiki directory of AI-text detectors.

Overview

QuillBot is widely known for its paraphrasing and grammar tools, but it also offers a separate, free AI detector (the subject of this entry, not the paraphraser). It estimates the likelihood that a passage was AI-generated and requires no signup for checks below a word limit. QuillBot and Scribbr are both owned by Learneo and share detection technology, so their detectors produce comparable results. Its audience is broad, skewing toward students and general writers.

Accuracy in practice

QuillBot markets the detector as most reliable on longer English text and does not commit to a single public accuracy figure. Independent testing generally places it around 75–80% on long-form, unedited AI content (respectable for a free tool but behind the top-tier detectors), and reviewers note a tendency to over-predict AI, raising the chance of false positives on genuine human writing. Accuracy drops on short inputs and on paraphrased or humanized text. The score is a probability rather than proof.

Summary

QuillBot’s free detector is an accessible option that works best on longer passages and mirrors the Scribbr engine. Its documented false-positive tendency and mid-range accuracy mean its output is best treated as a signal rather than a definitive verdict.