Undetectable AI is the go-to specialist for bypassing AI detectors (like Turnitin or GPTZero) by rewriting text with human-like imperfections. Quillbot, conversely, is the ultimate writing assistant for polishing grammar, improving fluency, and paraphrasing without hiding its AI nature. Choose Undetectable AI to avoid flags; choose Quillbot to write better.
Undetectable AI rewrites text to bypass detectors
Undetectable AI is a specialized “stealth” tool designed to rewrite AI-generated text specifically to bypass detection systems. Unlike standard paraphrasers, it uses a unique “humanization engine” that alters syntax and intentionally introduces subtle, natural imperfections to mimic human writing patterns, helping content pass checks from strict detectors like Turnitin and Originality.ai.
Quillbot enhances writing clarity and fluency.
Quillbot is a comprehensive AI writing assistant that enhances clarity, fluency, and vocabulary. It offers advanced paraphrasing with multiple modes (Standard, Fluency, and Academic) to refine text quality without necessarily hiding its AI origins. Ideally suited for students and professionals, it integrates seamlessly into workflows to fix grammar, summarize content, and polish drafts.
Both tools manipulate text, but their end goals are opposite: one hides the AI, the other polishes it. Undetectable AI sacrifices some grammatical perfection for “stealth,” while Quillbot prioritizes flawless, professional output that may still trigger detectors. The table below highlights the winner for each specific need.
Fast Comparison Table
| Feature | Undetectable AI | Quillbot |
Winner |
| Primary Goal | Bypass AI Detection | Improve Writing Quality | Depends on Goal |
| Core Engine | Humanization (mimics human imperfections) | Paraphrasing (polishes text) | Tie |
| Customization | Readability Levels (High School – PhD) | Synonym Slider + Freeze Words | Quillbot |
| AI Detection | High Success Rate (~99% bypass) | Low Success Rate (Often detected) | Undetectable AI |
| Integration | Web & Chrome Extension | Word, Chrome, macOS, Android | Quillbot |
| Cost Value | Pay for Stealth (Word Credits) | Pay for Utility (Unlimited) | Quillbot |
Winner: Tie (Different Purposes)
Quillbot leads in versatility with 9 predefined modes—including the new Humanizer, Academic, Formal, and Shorten—plus unlimited Custom modes for Premium users. The platform has precise control over tone, from professional polish to natural simplicity. While the free plan grants access to Standard and Fluency modes, the Premium plan unlocks advanced tones like Formal and Academic for specific audiences.
Quillbot offers 9 versatile paraphrasing modes.
In contrast, Undetectable AI operates on a dedicated Humanization Engine designed specifically for evasion, not just style. It rewrites text by altering syntax and injecting intentional imperfections to break the statistical patterns (perplexity) that detectors flag. While Quillbot’s new Humanizer mode makes text sound natural to readers, Undetectable AI remains the specialized choice for bypassing strict forensic scanners like Turnitin.
Undetectable AI alters syntax to bypass detection.
Winner: Quillbot
Quillbot offers superior granular control through its signature Synonym Slider and Freeze Words feature. The slider lets you adjust the density of vocabulary changes in real-time—from subtle tweaks to a complete overhaul—while “Freeze Words” ensures specific keywords or technical jargon remain untouched. Such precision is crucial for SEO writers and academics who need to preserve specific terminology.
Quillbot allows precise control via the Synonym Slider.
Undetectable AI takes a broader approach with Readability Levels and Purpose Presets. Instead of word-level control, you select a target audience (e.g., High School, University, Doctorate) or a content type (Essay, Marketing). While effective for matching a general “vibe,” it lacks the manual precision of Quillbot, forcing users to trust the AI’s automated choices for vocabulary and structure changes.
Undetectable AI adjusts tone via readability levels.
Winner: Undetectable AI
Detection evasion is the decisive battleground where Undetectable AI dominates. In independent tests, content processed by Undetectable AI consistently achieves a <1% detection rate across major scanners like Turnitin, Originality.ai, and GPTZero. Its algorithm is specifically trained to mimic the “perplexity” and “burstiness” of human writing, effectively rendering the text invisible to detection software.
Undetectable AI achieves a <1% detection rate.
Quillbot, while a powerful rewriter, performs poorly in this specific metric. Because it focuses on creating “flawless” and grammatically perfect sentences, it often leaves behind the statistical signatures that AI detectors look for. Tests frequently show Quillbot-paraphrased text triggering >70% AI detection scores, making it unreliable for users whose primary goal is to avoid being flagged.
Quillbot often triggers >70% AI detection scores.
Winner: Quillbot
Quillbot is built to live where you write. It offers deep integration across virtually all platforms, including a Chrome Extension, Microsoft Word Add-in, macOS desktop app, and Android/iOS keyboards. It allows users to paraphrase, summarize, and check citations directly within their document or email client without ever switching tabs, creating a seamless and efficient workflow.
Quillbot offers deep integration across platforms.
Undetectable AI offers a more limited ecosystem, primarily functioning as a web-based destination or via a basic Chrome extension. While it provides an API for developers, the average user must copy-paste text back and forth between their document and the Undetectable AI website. It lacks the direct “in-doc” editing capabilities that make Quillbot such a productivity powerhouse for daily writing tasks.
Undetectable AI lacks direct app integration.
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|
Feature |
Undetectable AI |
Quillbot |
| Pros | ✅ Bypasses major AI detectors.
✅ Mimics natural human writing. ✅ Offers a money-back guarantee. ✅ Adjusts readability levels. |
✅ Polishes grammar perfectly.
✅ Unlimited words for Premium. ✅ Integrates deep into apps. ✅ Includes extra writing tools. |
| Cons | ❌ May cause grammar errors.
❌ Pricing based on word limits. ❌ Lacks citation tools. ❌ No direct app integration. |
❌ Easily flagged by detectors.
❌ Output feels robotic. ❌ Limited structural rewriting. ❌ Free plan has strict limits. |
|
Feature |
Undetectable AI |
Quillbot |
| Free Access | One-time Trial: ~250 words total.
(No credit card required) |
Forever Free: 125 words per run.
(No credit card required) |
| Pricing Model | Pay-per-Word: Monthly credit limit.
(e.g., $5/mo for 10,000 words) |
Flat Subscription: Unlimited usage.
(e.g., $4.17/mo billed yearly) |
| Refund Policy | Refund only if the content is flagged by AI detectors (Must provide proof). | 3-Day Money-Back Guarantee (No questions asked). |
| Flexibility | Can upgrade the word limit instantly if you run out of credits. | Upgrade/Downgrade anytime; changes apply next billing cycle. |
| Key Insight | High Cost-Per-Word: Best for specific, high-stakes projects requiring guaranteed evasion. | Best Value: Ideal for heavy, daily users who need unlimited rewriting without “metered” limits. |
Quillbot Pricing Plan
Undetectable AI Pricing Plan
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