Humanized AI Text Detector

Detect AI text run through humanizers like Undetectable AI, QuillBot, HIX Bypass, and StealthWriter. These tools are built to fool detectors — here's what still gets through.

Undetectable AIFree Forever55–65% DetectionNo Login

AI Text Detector

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Narrative Academic
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Signal Breakdown tap to expand

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Accuracy note: Browser-based detectors achieve ~70–80% accuracy. Use as a screening tool, not sole evidence of AI use. How it works →

What Survives Humanization

AI humanizers swap vocabulary and reorder sentences — but four deeper patterns consistently survive the process.

Phrase Loop Persistence

Humanizers swap words but don't fix phrase-level repetition. Our N-gram detector catches AI phrases (3–5 word combinations) repeated 10+ times in the same text — something humanizers consistently miss because they operate word-by-word.

Subject Monotony Survival

Humanizers change the words but not the structural monotony. AI writes "She walked. She thought. She felt." — humanizers change those words but every sentence still starts with the same subject structure. The pattern survives.

Semantic Circularity

The AI "not sure" loop: "While it's difficult to say... it is clear that... though of course it depends... but ultimately it seems..." This circular hedging appears even after humanization because it's deep structural, not lexical.

Transition Word Persistence

AI humanizers target vocabulary spikes but "Furthermore", "Moreover", "Additionally" often persist — humanizers don't classify transitions as AI markers. Our detector specifically checks transition density as a separate signal.

What Humanizers DO Defeat (Be Honest)

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Humanized AI is the hardest category. Our 55–65% rate is honest — humanizers were built specifically to fool detectors. Use the signal breakdown to understand WHY a score is what it is.

Humanizers specifically defeat:

  • Vocabulary spike detection (they swap "delve" for "explore", etc.)
  • Superficial sentence structure detection (they reorder clauses)
  • Basic burstiness signals (they vary sentence lengths)

Residual detection rates by tool tested:

Undetectable AI (~55%)QuillBot AI (~58%)HIX Bypass (~52%)StealthWriter (~60%)Humanize.pro (~57%)

Detection Rates by Humanization Level

Unhumanized AI (baseline)75–90%
Light humanization (QuillBot paraphrase)60–72%
Medium humanization (Undetectable AI)50–62%
Heavy humanization (multi-tool)30–50%

Humanized AI Detector FAQ

Humanizers specifically target vocabulary spikes and sentence structure — the main signals most detectors use. They systematically replace flagged words and vary sentence patterns. What they miss: phrase loops, semantic circularity, and transition persistence.
Phrase loop persistence (N-gram repetition), subject monotony (same sentence structure pattern), semantic circularity (circular hedging loops), and transition word persistence — these require deep structural rewrites that humanizers don't do.
Yes, with ~55% residual detection. Undetectable AI is the most advanced humanizer tested — it targets vocabulary and structure specifically. Phrase loops and transition persistence are the surviving signals our detector catches.
Yes, as a screening tool. A 55% score means humanized text still scores higher than genuine human writing. Use the individual signal breakdown — if phrase loops and transition persistence both fired, that's meaningful even at a lower overall score.