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8 Signals Analyzed
Human writing varies sentence lengths dramatically (high CV). AI produces uniform, similarly-sized sentences (low CV).
LLMs consistently use specific vocabulary: "multifaceted," "nuanced," "delve into," "leverage," "actionable insights." These are measurable fingerprints.
AI starts sentences with transition formulas: "Furthermore," "Moreover," "It is important to note." Human writing uses diverse, organic starters.
Contractions, first-person voice, colloquial fillers, parenthetical asides, and sentence fragments are strongly human-associated. AI avoids all of these.
AI models are trained to sound "impressive" and use more polysyllabic words. Human writing naturally varies syllable complexity.
Type-token ratio: human writers use a wider unique vocabulary relative to text length. AI repeats safe, high-frequency words.
AI generates paragraphs of similar length and structure. Human writing has organic variation in paragraph depth and rhythm.
AI defaults to formal register even when casual context would be natural. Measured by ratio of formal transition words to total discourse markers.
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Frequently Asked Questions
How does the AI detector work?
The detector analyzes 8 signals: Sentence Burstiness (length variation — AI is uniform, humans vary), AI Vocabulary Fingerprints (93 LLM-specific words like "multifaceted" and "leverage"), Sentence Starter Patterns, Human Voice Signals (contractions, fillers, fragments), Syllable Complexity, Vocabulary Diversity, Paragraph Uniformity, and Lexical Formality.
Can it detect ChatGPT, GPT-4, and Claude?
Yes. The detector targets structural and vocabulary patterns common to all large language models — ChatGPT, GPT-4, GPT-4o, Claude, Gemini, and Llama. It detects LLM fingerprints rather than model-specific signatures.
How accurate is this free AI detector?
ChatGPT-style text typically scores 75–90%+. Clearly human casual writing scores 10–25%. Academic writing may score higher (40–60%) due to formal structural similarities with AI output. No AI detector is 100% accurate — always use scores as probabilistic signals, not definitive proof.
Should AI detection scores be used as proof?
No. AI detectors should never be used as sole evidence of AI authorship. Detection scores are probabilistic estimates based on statistical patterns. Use them as one signal among many when evaluating text authenticity.
What does a high AI probability score indicate?
A score above 65% indicates multiple AI signals present: formulaic vocabulary, uniform sentence lengths, transition word overuse, and absence of human markers like contractions and sentence fragments. Scores above 80% suggest very likely AI-generated content.