🧠 Introduction
AI detection has grown into one of the most widely used technologies in both education and professional writing.
Out of the hundreds of detectors that now exist, only a few have reached massive global adoption.
This article breaks down the Top 5 Largest AI Detectors by User Count, based on:
- Publicly disclosed user numbers
- Platform-wide traffic and engagement
- Market share and adoption across schools and workplaces
The top five platforms are:
- Turnitin
- ZeroGPT
- QuillBot
- GPTZero
- Grammarly
Together, these tools serve hundreds of millions of users and shape the standards of AI detection worldwide.
🥇 1. Turnitin — 71+ Million Students
Turnitin is the largest and most widely used AI detector in the world.
It powerfully dominates education because it is integrated directly into:
- Canvas
- Blackboard
- Brightspace
Turnitin reports serving over 71 million students, giving it far more reach than any other AI detector.
Why Turnitin Is #1
- Integrated in thousands of universities
- Deep LMS integrations
- Long-standing academic trust
- Comprehensive AI and plagiarism scanning
Turnitin will likely remain the largest AI detector for years due to institutional adoption.
🥈 2. ZeroGPT — Estimated 30+ Million Users
ZeroGPT does not publish exact user numbers, but market analysis places its audience at 30 million+ users.
Why ZeroGPT Exploded
- Completely free detector
- Extremely simple interface
- Viral adoption among students
- Massive search-engine visibility
ZeroGPT became the go-to “public” AI detector outside academic systems.
🥉 3. QuillBot AI Detector — 15+ Million Users (Estimated)
QuillBot’s platform has over 50 million users total.
Based on traffic and internal tool usage, the AI detector likely sees 15 million+ users.
Why QuillBot Ranks So High
- Already trusted by students for rewriting
- Built into a large writing ecosystem
- Easy to access without an account
- Strong brand reputation
QuillBot’s detector benefits enormously from the platform’s long history and large user base.
🏅 4. GPTZero — 10+ Million Users
GPTZero reports over 10 million users, making it one of the largest AI detection platforms.
Why GPTZero Grew So Quickly
- Early mover in AI detection
- Good accuracy reputation
- Teacher-focused features
- Transparent detection scoring
GPTZero is heavily used in education and by professionals who want a dedicated AI detector rather than a full writing suite.
🏅 5. Grammarly AI Detector — 8+ Million Estimated Users
Grammarly as a whole has 40 million+ users, making it one of the largest writing platforms in the world.
While Grammarly does not publish detector-specific numbers, industry estimates place its AI Detector usage at 8 million+ users.
Why Grammarly Ranks #5
- Trusted writing assistant for over a decade
- AI detection built directly into grammar checks
- Huge base of students and professionals
- Ultra-clean interface and extremely easy to use
Even though Grammarly’s main product is not AI detection, its massive platform gives the detector significant reach.
📊 Summary Table — Biggest AI Detectors by User Count
| Rank | AI Detector | Estimated User Count | Notes |
|---|---|---|---|
| 1 | Turnitin | 71M+ | Largest institutional detector |
| 2 | ZeroGPT | 30M+ | Most popular free public detector |
| 3 | QuillBot AI Detector | 15M+ | Powered by 50M+ QuillBot users |
| 4 | GPTZero | 10M+ | One of the most widely used AI detection tools |
| 5 | Grammarly AI Detector | 8M+ | Built into a 40M+ user writing platform |
🧩 Why These Platforms Dominate
There are two main categories of AI-detection giants:
1. Established Writing & Academic Platforms
These tools already had tens of millions of users:
- Turnitin
- QuillBot
- Grammarly
When they added AI detection, adoption was instant.
2. Public AI-Detection Startups
These platforms rose because AI detection became a concern:
- ZeroGPT
- GPTZero
Both had massive first-mover advantage and quickly became the default detectors online.
🎯 Final Thoughts
The AI detection market is crowded, but these five platforms stand out as the largest AI detectors.
- Turnitin dominates education
- ZeroGPT & GPTZero dominate public usage
- QuillBot & Grammarly dominate writing platforms
🚀 How to Bypass AI Detectors
AI detectors rely on pattern-based signals and often disagree with each other, which can result in false positives.
If you need to bypass AI detectors and humanize AI-generated text, use TwainGPT.