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October 2026 review · same 50 texts

Undetectable.ai vs Grubby

In the October 2026 HumanizerEval review, Undetectable.ai and Grubby rewrote the same 50 English texts. Undetectable.ai cleared all 6 detectors on 1 of them; Grubby on 0. The difference is mostly Pangram: on 16 samples Undetectable.ai passed it where Grubby failed, and the reverse happened on 1. On Originality.ai Turbo, Originality.ai 5.0, ZeroGPT and Winston AI the two were close to even.

Per-sample agreement

Per-sample agreement, October 2026. Counts are out of the 50 shared samples, computed at the 50% human-score threshold. Margin counts the samples only one tool passed, higher count first.
DetectorPassed more oftenMarginBoth passedNeither passed
Pangram 4.1Undetectable.ai16 to 1429
GPTZero 2026-10-07-baseUndetectable.ai10 to 1336
Originality.ai TurboGrubby1 to 0490
Originality.ai 5.0 model-5.0Undetectable.ai2 to 0048
ZeroGPT defaultUndetectable.ai2 to 0480
Winston AI 5.0Tied0 to 0500
All 6 detectorsUndetectable.ai1 to 0049

Every count is computed from scores.csv at build time, not transcribed. “Neither passed” counts the texts that defeated both tools; on Pangram that was 29 of 50 here.

Quality and output discipline

Quality and output discipline, October 2026.
MeasureUndetectable.aiGrubby
32%76%
28%64%
90%100%
60%78%
1.271.19
111
00
University / General Writing / More Human, v11srAcademic
Websiteundetectable.ai grubby.ai

On per-sample quality scores, Undetectable.ai scored higher on 3 samples, Grubby on 38, and the two tied on 9. Grubby’s output was shorter on 33 of 50 samples; mean length ratios were 1.27 and 1.19, or 27% longer than the input and 19% longer than the input respectively.

Where each one outperforms the other

Undetectable.ai

  • Pangram: passed 20 of 50 against 5, including 16 samples where Grubby failed, against 1 the other way.
  • GPTZero: passed 43 of 50 against 34, including 10 samples where Grubby failed, against 1 the other way.
  • Originality.ai 5.0: passed 2 of 50 against 0, including 2 samples where Grubby failed, against 0 the other way.
  • ZeroGPT: passed 50 of 50 against 48, including 2 samples where Grubby failed, against 0 the other way.

Grubby

  • Pangram: passed 1 sample where Undetectable.ai failed, even though it was detected more often overall, passing 5 to 20.
  • GPTZero: passed 1 sample where Undetectable.ai failed, even though it was detected more often overall, passing 34 to 43.
  • Originality.ai Turbo: passed 50 of 50 against 49, including 1 sample where Undetectable.ai failed, against 0 the other way.
  • Winston AI: tied at 50 of 50 but on a higher mean human score, 99.7% to 98.5%. It passed 0 samples where Undetectable.ai failed.
  • Factual consistency: 76% against 32%.
  • Naturalness: 64% against 28%.
  • Syntax integrity: 100% against 90%.
  • Stance preservation: 78% against 60%.
  • Length: shorter output on 33 of 50 samples, which matters under a word limit.

Undetectable.ai vs Grubby FAQ

Is Undetectable.ai better than Grubby?

In the October 2026 HumanizerEval review, Undetectable.ai cleared all 6 detectors on 1 of the 50 shared samples and Grubby on 0. On Originality.ai Turbo, Originality.ai 5.0, ZeroGPT and Winston AI the two were within 6 points of each other. Quality ran 3 samples to 38, with 9 ties.

Which humanizer is best for Pangram, Undetectable.ai or Grubby?

Undetectable.ai. In October 2026, Undetectable.ai passed Pangram on 20 of the 50 shared samples and Grubby on 5. On 16 samples Undetectable.ai passed where Grubby failed; the reverse happened on 1. Both failed on 29.

Which humanizer changes the text less?

Grubby. It scored higher on per-sample quality on 38 of 50 samples, against 3. Undetectable.ai’s outputs averaged 1.27× the input length and passed factual consistency on 32%; Grubby’s averaged 1.19× and passed on 76%. On stance preservation the split was 60% to 78%. Grubby produced the shorter output on 33 of 50 samples.

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