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Undetectable.ai and StealthGPT are two of the most marketed AI humanizers in 2026. Both promise to bypass AI detectors, but they differ in pricing model, quality consistency, and breadth of workflow support. This comparison breaks down the real trade-offs — and shows where SynthQuery's integrated detect-and-humanize approach beats both.
Undetectable.ai wins on brand and flat pricing. StealthGPT wins on mobile app and aggressive bypass marketing. SynthQuery beats both on structural workflow: you humanize AND verify with an integrated detector in the same interface, under one flat plan that also includes plagiarism and readability.
| Feature | Undetectable Ai | Undetectable.ai vs StealthGPT |
|---|---|---|
| Pricing model | Flat subscription | Undetectable.ai: flat. StealthGPT: credit-based (burns fast) |
| Humanizer modes | 7 modes with readability targeting | Undetectable.ai: multiple intensities. StealthGPT: multiple modes |
| Integrated AI detector | Yes — built-in | Neither has integrated detection |
| Plagiarism checker | Yes — billions of sources | Neither |
| Readability analysis | 20+ formulas | Neither |
| Mobile app | Responsive web | Undetectable.ai: web. StealthGPT: native mobile |
| Brand recognition | Growing | Undetectable.ai: large. StealthGPT: aggressive marketing |
| Free tier | Free tier with core tools | Both: trial only, no meaningful free tier |
| API | REST API | Both offer API |
| Character limit per request | Up to 100K on Pro | Both: typically 10-15K per request |
| Total tools in subscription | 50+ (SEO, image, business) | Both: humanizer-only |
| Plan | Undetectable Ai | Undetectable.ai vs StealthGPT |
|---|---|---|
| Free | Free tier | None meaningful |
| Starter | $12/mo | Undetectable.ai $14.99/mo; StealthGPT credit packs from $14.99 |
| Pro | $29/mo | Undetectable.ai premium tiers; StealthGPT larger credit packs |
Writers and agencies who want humanization, detection verification, plagiarism, and readability in one subscription with flat pricing.
Undetectable.ai for writers wanting a large, trusted humanizer brand. StealthGPT for users who prefer a mobile-first humanizer experience.