| Undetectable AI | StealthGPT | |
|---|---|---|
| Starting price | $9.99/mo | $14.99/mo |
| Free tier | 250 words | 0 words |
| Bundled detector | Yes | No |
| Founded | 2022 | 2023 |
| Best for | Teams that want one tool to both check and rewrite content across multiple AI models. | Long-form academic or research writing where sentence-level restructuring matters more than speed. |
Price: Undetectable AI is cheaper to start, at $9.99/mo vs $14.99/mo.
Undetectable AI: $9.99/mo for the entry tier; higher tiers scale by word volume.
StealthGPT: Plans from $14.99/mo; per-word bundles available for one-off use.
Free tier: Undetectable AI offers a more generous free tier (250 words).
If you just want to test either tool before paying, Undetectable AI's 250-word allowance gives you more room to evaluate quality.
Detection performance
Undetectable AI: Frequently cited as a top-tier performer against GPTZero and Originality.ai, though results vary by source text length and topic.
StealthGPT: Positioned and marketed specifically around Turnitin's originality algorithm rather than general-purpose detectors.
AI detector included: Undetectable AI bundles a built-in detector; StealthGPT does not.
Strengths at a glance
Undetectable AI
- Runs output against multiple detector models before returning it
- Supports long-document processing without manual chunking
- Adjustable readability and purpose settings (story, essay, article, email)
StealthGPT
- Generates and rewrites in one pass, so you can skip a separate AI writer
- Aggressive sentence-level restructuring rather than word substitution
- No word cap on paid plans — good for full-length papers
Our verdict
Choose Undetectable AI if: teams that want one tool to both check and rewrite content across multiple ai models. Choose StealthGPT if: long-form academic or research writing where sentence-level restructuring matters more than speed.