Make AI text read
naturally for QuillBot AI Detector.
The QuillBot AI Detector is QuillBot's free tool for estimating whether text was written by AI — a separate feature from the paraphraser QuillBot is best known for. Here's how its scoring actually works, what its false-positive record looks like, and the honest version of what a humanizer can and can't do about it.
How QuillBot AI Detector works
QuillBot's AI detector estimates the probability that a passage was generated by a large language model such as ChatGPT, Claude, or Gemini, returning a percentage rather than a yes-or-no answer. Like most detectors it reads statistical signals — perplexity, how predictable each word is to a model, and burstiness, the variation in sentence complexity. Highly predictable, evenly paced text reads as machine-written, while human writing tends to vary more.
False positives
QuillBot's detector returns a probability, not proof, and AI detectors broadly misfire on genuinely human writing. False positives cluster on formulaic, simple, or non-native and ESL English, whose low perplexity resembles AI output. A high AI percentage is a signal worth a second look, not a verdict — treat any single score that way.
What a rewrite actually looks like
Here's the same paragraph before and after Humanizer — the structure, rhythm, and word choice change, not just a few swapped synonyms. The percentage is Sapling's AI-likelihood estimate, shown on every rewrite. It's a signal, not a guarantee against QuillBot AI Detector.
AI has become an integral part of modern content creation. With the advent of large language models, the ability to generate high-quality text has been revolutionized, allowing for unprecedented efficiency in writing workflows.
Recent advances in large language models have genuinely reshaped how people write. What used to take days of drafting can now happen in an afternoon — though how much it helps still depends on the field, and we're all figuring out the limits.
Humanize your text.
Right here, right now.
Paste up to 1,500 characters, pick a mode, and get a real rewrite with an AI-detector score. No account, no card.
Your rewrite will appear here.
Free tool runs Claude Haiku, one pass. Pro (app & web) uses the stronger model with a detector-guided retry loop, longer text, and unlimited rewrites.
Humanize free — then get the app
Try the rewriter right here, no signup. Get the native Mac & iPhone app for unlimited rewrites, longer text, and the stronger model.