| Undetectable AI | WriteBros.ai | |
|---|---|---|
| Starting price | $9.99/mo | $1.99/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. | Budget-conscious, high-volume users willing to run text through multiple passes for the best score. |
Price: WriteBros.ai is cheaper to start, at $1.99/mo vs $9.99/mo.
Undetectable AI: $9.99/mo for the entry tier; higher tiers scale by word volume.
WriteBros.ai: Lite plan from $1.99/mo (30k words); Plus $9.99/mo; Pro $15/mo with API access.
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.
WriteBros.ai: Achieved a 100% human GPTZero score in testing, but only after four iterative rewriting rounds rather than a single pass.
AI detector included: Undetectable AI bundles a built-in detector; WriteBros.ai 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)
WriteBros.ai
- By far the lowest starting price of any tool reviewed here
- Removes common AI 'tells' like overused em-dashes and uniform sentence rhythm
- Pro tier includes API access for automated pipelines
Our verdict
Choose Undetectable AI if: teams that want one tool to both check and rewrite content across multiple ai models. Choose WriteBros.ai if: budget-conscious, high-volume users willing to run text through multiple passes for the best score.