AI Content Detector: Check ChatGPT, Gemini & Copilot Text
AI content detector online: check if text was written by ChatGPT, Gemini, or Copilot with perplexity and burstiness analysis.
Updated 2026-08-26
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Features
- Analyze text for AI-generated content using multiple statistical metrics
- Perplexity analysis: measures how predictable the text is to language models
- Burstiness analysis: detects uniform sentence patterns typical of AI
- Vocabulary diversity scoring: Type-Token Ratio and unique word analysis
- AI keyword detection: identifies phrases commonly used by LLMs
- Sentence-level highlighting: color-code sentences by AI probability
- Real-time analysis: results update as you type or paste text
- Supports both English and Chinese text analysis
- Copy or export analysis results for documentation
How to Use
- 1Paste or type text into the input area (minimum 100 characters recommended).
- 2Click 'Analyze' or wait for automatic analysis to complete.
- 3Review the overall AI probability score at the top.
- 4Check individual metrics: Perplexity, Burstiness, Vocabulary Diversity, AI Keywords.
- 5Read the detailed explanation for each metric to understand the analysis.
- 6Review sentence-level highlights; red indicates higher AI probability.
- 7Copy the analysis report for your records or documentation.
- 8For best results, use texts longer than 255 characters.
Frequently Asked Questions
How accurate is this detector?
This tool uses statistical heuristics (perplexity, burstiness, vocabulary analysis) with fixed verdict thresholds: scores below 0.3 are labeled human, 0.3-0.55 uncertain, 0.55-0.75 likely AI, and 0.75+ AI. These are less powerful than deep-learning detectors like GPTZero, so treat the verdict as a screening signal, not a definitive judgment, especially for text under 255 characters, where the confidence label is low.
What is perplexity?
Perplexity measures how 'surprised' a language model would be by the text. AI-generated text typically has lower perplexity because LLMs tend to choose the most probable words, making the text more predictable. Human text usually has higher perplexity due to more varied and creative word choices.
What is burstiness?
Burstiness measures the variation in sentence length and complexity. Human writing tends to have high burstiness: a mix of short and long sentences, complex and simple structures. AI text often has low burstiness: sentences are more uniform in length and structure.
Can this detect all AI-generated content?
No. This tool works best with: 1) Texts longer than 255 characters, 2) English or Chinese text, 3) Texts generated by standard LLMs (GPT, Claude, etc.). It may struggle with: paraphrased AI text, mixed human-AI text, or text from specialized/domain-specific LLMs.
How does this compare to Turnitin or Copyleaks detection?
Commercial services like Turnitin and Copyleaks run deep-learning models trained on millions of human and AI samples and can cross-check against their databases; this tool uses statistical heuristics (perplexity, burstiness, vocabulary) that run locally. Treat this as a free screening signal; for official or graded submissions, use the tool your institution requires.
Can I check text from a PDF with this tool?
Yes, the tool accepts pasted text, so extract the text from the PDF first (copy it in a PDF reader, or use a PDF text extractor) and paste it here. Text under 100 characters carries little signal; below 255 characters the confidence label is marked low, so paste the full document for a meaningful score.
Why is my text flagged as AI when I wrote it myself?
False positives can occur when: 1) You use formal/academic writing style, 2) Your text follows predictable patterns, 3) You use common phrases or structures, 4) The text is short (less reliable). If you're confident the text is human-written, the detector may be wrong.
What AI keywords does the tool detect?
The tool checks 71 phrases in total (43 English and 28 Chinese) that LLMs use frequently, such as 'Furthermore', 'In conclusion', 'Moreover', 'It is important to note', 'Delve into', 'Tapestry', 'Landscape', 'Realm', 'Embark', plus their Chinese equivalents. These are not definitive proof of AI generation but are statistical indicators.
Does it work with Chinese text?
Yes. The tool supports both English and Chinese text analysis. For Chinese, it uses character-level analysis and Chinese-specific tokenization via the browser's built-in Intl.Segmenter API.
What should I do with the results?
Use the results as one data point in your evaluation: 1) High AI probability + clear patterns → investigate further, 2) Low AI probability → likely human-written, 3) Mixed results → use judgment. Never rely solely on automated detection for important decisions.
Why is AI detection less reliable for Chinese text?
Chinese is analyzed with character-level statistics, but the perplexity and burstiness patterns this tool uses were established from English prose, so AI-generated Chinese and translated-style Chinese often score in the same range. Short Chinese text is even less reliable. Treat the result as a rough signal for Chinese input and check the confidence label; it is marked low below 255 characters.
Why does the score change when I edit or re-paste the same text?
Every metric is computed over the exact text you provide: adding or removing characters changes the token window, sentence segmentation, and keyword counts, so a slightly different input can move the score across a threshold. For a stable result, analyze the complete, unedited text; results below 255 characters carry a low-confidence label for exactly this reason.
What is the difference between perplexity and burstiness?
Perplexity focuses on word predictability: AI tends to choose high-probability words, so AI text usually has lower perplexity. Burstiness focuses on sentence structure variation: AI sentences are uniform in length, so burstiness is low. The two metrics look at AI traits from different angles and work best when combined.