HumanizerEval

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September 2026 review · same 50 texts

Undetectable.ai vs BypassGPT

In the September 2026 HumanizerEval review, Undetectable.ai and BypassGPT rewrote the same 50 English texts. Undetectable.ai cleared all 5 detectors on 15 of them; BypassGPT on 0. The difference is mostly GPTZero: on 20 samples Undetectable.ai passed it where BypassGPT failed, and the reverse never happened. On ZeroGPT and 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 4.0Undetectable.ai16 to 0034
GPTZero 2026-09-13-baseUndetectable.ai20 to 0282
Originality.ai turboUndetectable.ai16 to 2311
ZeroGPT defaultTied0 to 0500
Winston AI 5.0BypassGPT1 to 0490
All 5 detectorsUndetectable.ai15 to 0035

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 34 of 50 here.

Quality and output discipline

Quality and output discipline, September 2026.
MeasureUndetectable.aiBypassGPT
26%22%
28%2%
94%94%
78%78%
1.211.12
70
00
University / General Writing / More Human, v11srEnhanced
Websiteundetectable.ai bypassgpt.ai

On per-sample quality scores, Undetectable.ai scored higher on 16 samples, BypassGPT on 11, and the two tied on 23. BypassGPT’s output was shorter on 35 of 50 samples; mean length ratios were 1.21 and 1.12, or 21% longer than the input and 12% longer than the input respectively.

Where each one outperforms the other

Undetectable.ai

  • Pangram: passed 16 of 50 against 0, including 16 samples where BypassGPT failed, against 0 the other way.
  • GPTZero: passed 48 of 50 against 28, including 20 samples where BypassGPT failed, against 0 the other way.
  • Originality.ai: passed 47 of 50 against 33, including 16 samples where BypassGPT failed, against 2 the other way.
  • Factual consistency: 26% against 22%.
  • Naturalness: 28% against 2%.

BypassGPT

  • Originality.ai: passed 2 samples where Undetectable.ai failed, even though it was detected more often overall, passing 33 to 47.
  • ZeroGPT: tied at 50 of 50 but on a higher mean human score, 97.2% to 95.0%. It passed 0 samples where Undetectable.ai failed.
  • Winston AI: passed 50 of 50 against 49, including 1 sample where Undetectable.ai failed, against 0 the other way.
  • Length: shorter output on 35 of 50 samples, which matters under a word limit.

Undetectable.ai vs BypassGPT FAQ

Is Undetectable.ai better than BypassGPT?

In the September 2026 HumanizerEval review, Undetectable.ai cleared all 5 detectors on 15 of the 50 shared samples and BypassGPT on 0. On ZeroGPT and Winston AI the two were within 6 points of each other. Quality ran 16 samples to 11, with 23 ties.

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

Undetectable.ai. In September 2026, Undetectable.ai passed Pangram on 16 of the 50 shared samples and BypassGPT on 0. On 16 samples Undetectable.ai passed where BypassGPT failed; the reverse never happened. Both failed on 34.

Which humanizer changes the text less?

Undetectable.ai. It scored higher on per-sample quality on 16 of 50 samples, against 11. Undetectable.ai’s outputs averaged 1.21× the input length and passed factual consistency on 26%; BypassGPT’s averaged 1.12× and passed on 22%. On stance preservation the split was 78% to 78%. BypassGPT produced the shorter output on 35 of 50 samples.

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