Free AI Detector
Paste any text and get an AI probability score. Same scoring engine that powers Metric37's humanizer.
How AI Detection Works
AI-generated text has a statistical fingerprint. Large language models like ChatGPT, Gemini, and Claude predict the most probable next word at each step, producing text with consistently low perplexity (predictable word choices) and low burstiness (uniform sentence structure). Human writing is messier — we vary our rhythm, make unexpected word choices, and mix short punchy sentences with longer complex ones.
Our detector analyzes these patterns using the same scoring engine that powers Metric37's humanizer. Paste any text, whether it is an essay, blog post, email, or report, and get an AI probability score from 0-100%, plus specific sentences flagged as most likely AI-generated.
AI Detection by Model
Different AI models have different detection patterns. Learn how detectable each one is:
Can AI detectors identify ChatGPT output? We explain how detection works on ChatGPT text, what patterns get flagged, and what you can do about it.
Google GeminiCan AI detectors identify Google Gemini output? Analysis of Gemini's detection patterns, accuracy rates, and how to produce more natural content.
ClaudeCan AI detectors identify text written by Claude? Analysis of Claude's unique patterns, detection rates, and how Claude differs from ChatGPT in detectability.
Microsoft CopilotCan AI detectors identify Microsoft Copilot output? Copilot uses GPT models under the hood — here's what that means for detection.
Perplexity AICan AI detectors identify Perplexity AI output? How Perplexity's search-augmented generation affects detectability.
Frequently Asked Questions
- How does AI detection work?
- AI detectors analyze two key statistical patterns in text: perplexity (how predictable word choices are) and burstiness (how varied sentence lengths and structures are). AI models like ChatGPT select the most probable next word at each step, producing text with consistently low perplexity and uniform burstiness. Human writing is naturally more unpredictable, with varied rhythms, unusual word choices, and mixed sentence complexity.
- How accurate is this AI detector?
- Accuracy is highest on unedited AI text over 200 words. It decreases on heavily edited text, short passages under 50 words, and text that mixes AI and human writing. No AI detector is 100% accurate, so treat scores as a probability, not a certainty.
- Which AI models can this detector identify?
- Our detector works on text from all major AI models including ChatGPT (GPT-4, GPT-5-mini), Google Gemini, Claude, Microsoft Copilot, Perplexity AI, and others. Detection is model-agnostic — it analyzes statistical patterns common to all large language models, not signatures specific to one model.
- Is this AI detector really free?
- Yes, completely free with no account required. You can analyze up to 10 texts per hour. The detector uses the same scoring engine as our paid humanization product. We offer it free because it is useful on its own, and some people want to fix what it finds.
- What should I do if my text scores high for AI?
- A high AI score means the text exhibits patterns typical of AI generation. To reduce detectability: vary your sentence lengths, add personal anecdotes or specific details, replace generic transitions, and break up overly structured paragraphs. For a faster approach, Metric37's humanization engine rewrites AI text to sound naturally human while preserving meaning.
- Can I embed this AI detector on my website?
- Yes. We provide a free embeddable widget you can add to any website with a single iframe tag. The embed is lightweight, responsive, and includes Metric37 branding. Scroll down on this page to find the embed code.
Embed on Your Site
Add a free AI detector to your blog or website. Just paste this code:
<iframe src="https://metric37.com/embed/detect" width="100%" height="500" frameborder="0" style="border-radius: 8px; border: 1px solid currentColor; opacity: 0.2;"></iframe>