Head-to-head comparison
Undetectable AI vs StealthGPT
Tested side by side with the same prompts, same detectors, same scoring. Here is how they compare on bypass rate, meaning preservation, readability, pricing, and which writer each tool actually suits best.
Undetectable AI
StealthGPT
Side-by-side scores
Both tools were tested with 30 identical prompts across 6 writing categories (academic essays, blog posts, marketing copy, news articles, application essays, discussion posts). Each output was scored by 5 independent AI detectors. Here is how the numbers compare:
| Metric | Undetectable AI | StealthGPT | Winner |
|---|---|---|---|
| Overall Score | 80.09 | 71.47 | Undetectable AI |
| Bypass Rate | 94.1% | 82.9% | Undetectable AI |
| Meaning Preservation | 72.2 | 67.7 | Undetectable AI |
| Readability | 100 | 100 | Tie |
| Penalties | -8 (length inflation) | -9 (meaning drift, length inflation, length deflation) | Undetectable AI |
Detector-by-detector results
Not all detectors work the same way. Here is how each tool performed against each of the 5 detectors we tested. The tool with the higher bypass score on each detector is highlighted.
Undetectable AI wins on 3 of 5 detectors. StealthGPT wins on 2.
Our verdict
Undetectable AI is the stronger overall performer in this matchup. Its bypass rate (94.1%) is higher than StealthGPT’s (82.9%), and it wins against 3 of the 5 detectors where there is a clear winner. The 8-point penalty for length inflation is a real issue, but even with that hit, Undetectable AI still finishes 8.6 points ahead on overall score.
StealthGPT is not a bad tool. It holds a meaningful advantage against Copyleaks and Originality.ai, which matters for users who specifically need to beat Turnitin (which uses Originality.ai’s detection engine). However, its penalty load of 9 points (meaning drift, length inflation, length deflation) is significant, meaning it is more likely to alter what your text actually says.
For most use cases, Undetectable AI is the better pick. The exception is workflows that specifically target Copyleaks or Originality.ai, where StealthGPT’s advantage gives it a genuine edge.
Pricing comparison
Price alone should not drive the decision, but it is worth knowing what you are paying for. Here is how these two compare on the entry-level monthly plan:
Free tier available
No free tier
Undetectable AI is 25% cheaper at $19/mo vs $25.50/mo. Undetectable AI offers a free tier; StealthGPT does not.
Who should pick which
Different tools suit different workflows. Here is a practical breakdown of when each tool is the better fit:
Pick Undetectable AI if…
- You want the higher overall score and broader detector coverage
- Raw bypass rate is your top priority (94.1% vs 82.9%)
- Meaning preservation matters to your workflow
- You want a free tier to test before subscribing
- Budget matters and you prefer the lower-priced option ($19/mo vs $25.50/mo)
Pick StealthGPT if…
- Copyleaks is your primary detection concern (83.3 vs 74.6)
- Originality.ai is your primary detection concern (78.8 vs 66.3)
- You have tested it yourself and prefer its specific output style
Related comparisons
Frequently asked questions
Is Undetectable AI better than StealthGPT?
In our independent testing across 5 AI detectors, Undetectable AI scored 80.09 overall compared to StealthGPT at 71.47. Undetectable AI wins on raw bypass rate (94.1% vs 82.9%) and leads on 3 of 5 detectors. The better choice depends on which specific detectors matter most to your workflow.
Which is cheaper, Undetectable AI or StealthGPT?
Undetectable AI starts at $19/month with a free tier. StealthGPT starts at $25.50/month.
Which AI humanizer is best for bypassing Turnitin?
Between these two tools, StealthGPT performs better against Originality.ai (which Turnitin’s detection is based on), scoring 78.8 compared to 66.3. If Turnitin specifically is your concern, StealthGPT has the edge in this matchup.
How were these AI humanizers tested?
We tested both tools using identical prompts across 6 writing categories (academic essays, blog posts, marketing copy, news articles, application essays, discussion posts), then ran every output through 5 independent AI detectors. Our full methodology is published at aihumanizertools.com/how-we-test-ai-humanizers/.
Next move
Use this comparison alongside the full reviews and our testing methodology before making a subscription decision.
Looking for the best AI humanizer? We tested 16 tools head-to-head. See our full Best AI Humanizer in 2026 ranking with bypass rates, pricing, and detailed reviews.