HumanizerEval

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September 2026 review · same 50 texts

Grubby vs RewriteAI

In the September 2026 HumanizerEval review, Grubby and RewriteAI rewrote the same 50 English texts. Grubby cleared all 5 detectors on 18 of them; RewriteAI on 13. The difference is mostly ZeroGPT: on 6 samples Grubby passed it where RewriteAI failed, and the reverse never happened. On Winston AI the two were close to even.

Per-sample agreement

Per-sample agreement, September 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 4.0Grubby10 to 6826
GPTZero 2026-09-13-baseGrubby6 to 2411
Originality.ai turboGrubby6 to 1430
ZeroGPT defaultGrubby6 to 0440
Winston AI 5.0Grubby2 to 0480
All 5 detectorsGrubby10 to 5827

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 26 of 50 here.

Quality and output discipline

Quality and output discipline, September 2026.
MeasureGrubbyRewriteAI
72%54%
46%40%
98%100%
94%94%
1.111.09
02
00
AcademicAPI default, passages of up to 280 words (300-word API limit)
Websitegrubby.ai rewriteai.com

On per-sample quality scores, Grubby scored higher on 23 samples, RewriteAI on 12, and the two tied on 15. RewriteAI’s output was shorter on 29 of 50 samples; mean length ratios were 1.11 and 1.09, or 11% longer than the input and 9% longer than the input respectively.

Where each one outperforms the other

Grubby

  • Pangram: passed 18 of 50 against 14, including 10 samples where RewriteAI failed, against 6 the other way.
  • GPTZero: passed 47 of 50 against 43, including 6 samples where RewriteAI failed, against 2 the other way.
  • Originality.ai: passed 49 of 50 against 44, including 6 samples where RewriteAI failed, against 1 the other way.
  • ZeroGPT: passed 50 of 50 against 44, including 6 samples where RewriteAI failed, against 0 the other way.
  • Winston AI: passed 50 of 50 against 48, including 2 samples where RewriteAI failed, against 0 the other way.
  • Factual consistency: 72% against 54%.
  • Naturalness: 46% against 40%.

RewriteAI

  • Pangram: passed 6 samples where Grubby failed, even though it was detected more often overall, passing 14 to 18.
  • GPTZero: passed 2 samples where Grubby failed, even though it was detected more often overall, passing 43 to 47.
  • Originality.ai: passed 1 sample where Grubby failed, even though it was detected more often overall, passing 44 to 49.
  • Syntax integrity: 100% against 98%.
  • Length: shorter output on 29 of 50 samples, which matters under a word limit.

Grubby vs RewriteAI FAQ

Is Grubby better than RewriteAI?

In the September 2026 HumanizerEval review, Grubby cleared all 5 detectors on 18 of the 50 shared samples and RewriteAI on 13. On Winston AI the two were within 6 points of each other. Quality ran 23 samples to 12, with 15 ties.

Which humanizer is best for Pangram, Grubby or RewriteAI?

Grubby. In September 2026, Grubby passed Pangram on 18 of the 50 shared samples and RewriteAI on 14. On 10 samples Grubby passed where RewriteAI failed; the reverse happened on 6. Both failed on 26.

Which humanizer changes the text less?

Grubby. It scored higher on per-sample quality on 23 of 50 samples, against 12. Grubby’s outputs averaged 1.11× the input length and passed factual consistency on 72%; RewriteAI’s averaged 1.09× and passed on 54%. On stance preservation the split was 94% to 94%. RewriteAI produced the shorter output on 29 of 50 samples.

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