AI Detector

Make AI text read
naturally for Scribbr.

Scribbr is a popular, student-facing AI detector offered as a free quick check, powered by a third-party detection model. It is widely used by students vetting their own essays before submission. 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 Scribbr works

Scribbr runs text through a third-party AI-detection model and returns an estimate of how likely the passage is AI-generated, highlighting the sentences it considers suspect. Like other detectors it keys on statistical signals such as perplexity, how predictable each word is to a language model, and the variation in sentence structure across a passage. Smooth, predictable output from ChatGPT, Claude, or Gemini tends to raise the AI estimate, while uneven human writing tends to lower it.

False positives

Scribbr is candid that AI detectors are not fully reliable, and false positives appear on genuinely human writing that reads cleanly or simply. Formulaic, short, or non-native English and ESL writing is especially likely to be flagged, since its low perplexity resembles AI output. Treat any single Scribbr result as a signal, not a verdict.

Where we stand We measure every rewrite against Sapling's AI detector and show you the score, so you can see how natural the output reads. We do not claim to pass Scribbr or any specific detector — the third-party model behind it changes over time and no humanizer, including ours, can guarantee passage at every moment. What Humanizer does is rewrite the rhythm, word choice, and structure that detectors key on, and let you match your own voice — not sell a fake "100% undetectable" promise.

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 Scribbr.

Before/after on a sample paragraph. Scores are Sapling estimates and will vary by text — Humanizer never promises a clean pass on any detector.
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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.

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FAQ

Scribbr questions, answered.

Scribbr's detector gives a probabilistic estimate, not a certainty, and Scribbr itself notes detectors are not fully reliable. It both misses AI text and flags human writing, so no Scribbr result should be treated as definitive proof.