| Undetectable AI | Grammarly AI Humanizer | |
|---|---|---|
| Starting price | $9.99/mo | $12/mo |
| Free tier | 250 words | 0 words |
| Bundled detector | Yes | No |
| Founded | 2022 | 2024 |
| Best for | Teams that want one tool to both check and rewrite content across multiple AI models. | Professionals who want more natural-sounding AI-assisted drafts without a dedicated bypass-focused tool. |
Price: Undetectable AI is cheaper to start, at $9.99/mo vs $12/mo.
Undetectable AI: $9.99/mo for the entry tier; higher tiers scale by word volume.
Grammarly AI Humanizer: Included in Grammarly Premium ($12/mo annual) and Business plans.
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.
Grammarly AI Humanizer: Grammarly is explicit that the feature is meant to improve natural tone rather than guarantee detector evasion, which sets it apart from bypass-first competitors.
AI detector included: Undetectable AI bundles a built-in detector; Grammarly AI Humanizer 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)
Grammarly AI Humanizer
- Built into an app most professionals already have installed (browser, desktop, Docs)
- Focuses on clarity and flow rather than aggressive detection evasion
- Backed by Grammarly's long-standing grammar and tone engine
Our verdict
Choose Undetectable AI if: teams that want one tool to both check and rewrite content across multiple ai models. Choose Grammarly AI Humanizer if: professionals who want more natural-sounding ai-assisted drafts without a dedicated bypass-focused tool.
Full Undetectable AI review → · Full Grammarly AI Humanizer review →