Head to head · September 2026 cycle
Stealth Writer vs Undetectable.ai
Stealth Writer finished 3.6 points ahead of Undetectable.ai in the September 2026 cycle, 75.39 to 71.75, ranking #2 against #6 in a field of 14. Stealth Writer scored higher on 4 of 5 detectors and 5 of 7 writing categories. Undetectable.ai came out ahead on GPTZero (72.4 vs 33.9), readability (61.7 vs 47.2) and application essay prompts (73.8 vs 62.5). The bypass-rate gap, 86.4 to 82.1, sits inside both tools' 95% confidence intervals, so treat bypass as a draw.
- Detectors
- 4 – 1
- Categories
- 5 – 2
- Components
- 3 – 2
Score components
What the overall score is made of: bypass rate weighs 42%, meaning preservation 32%, readability 16%, consistency across categories 10%. Output-quality penalties come off the total. How scoring works →
CIs overlap marks a gap that sits inside both tools' published 95% confidence intervals for that component; it may not survive another cycle.
Detector by detector
Share of each tool's outputs that a detector classified as human-written. Stealth Writer took 4 of 5.
Writing categories
Category score per writing context: bypass credit only for real rewrites, blended with the category's own meaning preservation and readability. Small categories swing; the prompt count is shown on each row. How category scores work →
Head-to-head history
Overall score in every cycle both tools were tested. Stealth Writer has finished ahead in 3 of 4 shared cycles.
| Cycle | Stealth Writer | Undetectable.ai | Margin |
|---|---|---|---|
| September 2026 | 75.39 #2 | 71.75 #6 | ← 3.6 |
| August 2026 | 69.83 #3 | 61.49 #8 | ← 8.3 |
| July 2026 | 68.07 #4 | 72.17 #2 | → 4.1 |
| June 2026 | 84.47 #1 | 80.09 #5 | ← 4.4 |
Where each one wins
Every measure above that one tool won outright, largest margin first within each group.
Stealth Writer
12 wins- Penalties Score −1.0 vs −6.0
- Consistency Score 81.4 vs 71.1
- Bypass rate Score 86.4 vs 82.1
- Copyleaks Detector 81.8 vs 74.3
- Originality.ai Detector 97.4 vs 91.7
- Winston AI Detector 80.3 vs 78.9
- ZeroGPT Detector 81.1 vs 80.4
- Blog Post Category 80.1 vs 57.5
- News Article Category 66.1 vs 51.8
- Discussion Board Category 84.0 vs 78.9
- and 2 more
Undetectable.ai
5 wins- Readability Score 61.7 vs 47.2
- Meaning preservation Score 82.1 vs 76.3
- GPTZero Detector 72.4 vs 33.9
- Application Essay Category 73.8 vs 62.5
- Academic Essay Category 86.0 vs 83.7
Questions people ask
Is Stealth Writer better than Undetectable.ai?
Stealth Writer finished 3.6 points ahead of Undetectable.ai in the September 2026 cycle, 75.39 to 71.75, ranking #2 against #6 in a field of 14. Stealth Writer scored higher on 4 of 5 detectors and 5 of 7 writing categories. Both tools ran the same 33 prompts, scored by the same 5 detectors, under methodology v1.2.0; every input, output and verdict is published.
Which bypasses AI detectors better, Stealth Writer or Undetectable.ai?
Stealth Writer posted the higher bypass rate, 86.4 vs 82.1, and scored higher on 4 of 5 detectors. Stealth Writer led on Originality.ai, Copyleaks, Winston AI and ZeroGPT; Undetectable.ai led on GPTZero. The overall bypass gap is inside both 95% confidence intervals, so it is not a reliable difference.
Do Stealth Writer and Undetectable.ai keep the original meaning?
Undetectable.ai preserved meaning better, 82.1 vs 76.3 on our 0–100 similarity scale, though the confidence intervals overlap. On readability, Undetectable.ai rated higher, 61.7 vs 47.2. Penalties this cycle: Stealth Writer −1.0, Undetectable.ai −6.0.