IsThisAI
Paste any text or email below. We'll give you a plain-language verdict on whether it was AI-written. No login, no history, complete privacy.
Accuracy & Limitations
No AI detector is 100% perfect. Our tool analyzes statistical patterns (perplexity and burstiness) that are characteristic of large language models like GPT-4 or Claude 3. It is highly accurate on long-form content, but short texts (under 100 words) may yield false positives or false negatives. Always use AI detectors as a signal, not as absolute proof.
Frequently Asked Questions
What is Perplexity?
Perplexity measures how predictable words are. AI models choose highly predictable words, resulting in low perplexity. Human writers are more erratic and use unusual word combinations, resulting in high perplexity.
What is Burstiness?
Burstiness measures the variation in sentence length. AI tends to write sentences of similar lengths and structures. Humans write in bursts—a long, complex sentence followed by a very short one.
Does this detect ChatGPT?
Yes. The heuristics are specifically tuned to identify the default writing styles of GPT-3.5, GPT-4, Claude, and Gemini.
Do you save my text?
No. Your text is processed securely in your browser and is never stored on our servers.