AI Text Detector: Spot AI-Written Content in Your Document
The AI text detector analyses the linguistic fingerprint of every sentence — perplexity, burstiness, token distributions — to distinguish human-written text from ChatGPT-generated and other AI output. Results in 15 minutes · from $0.29/page.
The Science Behind AI Text Detection
Understanding what makes AI text different at the linguistic level explains why the detector is effective.
Perplexity
Perplexity measures how "surprised" a language model is by each word choice. AI models generate text with very low perplexity — they always pick probable words. Humans write with much higher perplexity because we make unexpected but meaningful choices.
Burstiness
Human writing is "bursty" — some sentences are very short, others very long; some are simple, others complex. AI output is more uniform in length and complexity. The detector measures this variation across consecutive sentences.
Token Probability
Every word in AI text is chosen by sampling from a probability distribution. The detector analyses whether the pattern of word choices is consistent with high-probability sampling — a telltale sign of LLM output versus human writing.
How to Detect AI Text in 3 Steps
Upload Your Text
Submit your document as .docx, .pdf, or .txt. No account needed. Files are processed on German servers and never shared.
Linguistic Analysis Runs
The PlagAware engine analyses perplexity, burstiness and token distributions for every sentence in your document. This takes a few seconds per page.
Scored Report Delivered
Within 15 minutes you receive a PDF report with each sentence scored on the 25–75 scale. AI-flagged text is highlighted so you can find and revise it immediately.
Which AI Models Generate Detectable Text Patterns?
Every major language model leaves detectable statistical traces, because they all share the same fundamental generation mechanism: sampling words based on learned probability distributions.
The specific patterns vary by model family, which is why the detector is trained on text from multiple AI systems simultaneously.
- ChatGPT (GPT-3.5, GPT-4, GPT-4o)
- Claude (2, 3 Haiku, Sonnet, Opus)
- Google Gemini (Pro, Ultra)
- Llama 2, Llama 3 (Meta)
- Mistral, Phi, Falcon and others
Linguistic fingerprints
AI text is predictable by design — models always choose statistically likely words. This consistency is precisely what detectors measure.
The 25–75 AI Detection Score Explained
Every sentence in your document receives a score between 25 and 75, placing it on a spectrum from clearly human to clearly AI-generated.
Score 25–35: Human
This range indicates text with high perplexity and burstiness — the hallmarks of authentic human writing. Original arguments, personal observations and varied sentence structures fall here.
Score 40–55: Ambiguous
Text in this range may be AI-assisted, heavily formal, or written by a non-native speaker in an academic register. Context matters — a thesis methodology section may score here even when human-written.
Score 65–75: AI-Generated
This range indicates strong AI-generation signals: very low perplexity, highly uniform sentence structure, characteristic AI vocabulary. These sentences warrant review and revision.
Pricing — No Subscription, No Hidden Fees
Pay only for the pages you scan. Minimum order $0.90.
Plagiarism Scan
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- Results in 15 minutes
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Combo: Plagiarism + AI
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- Full plagiarism check included
- Sentence-level AI text detection
- Detects all major LLMs
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AI Scan
AI text detection only
- Linguistic pattern analysis
- Score per sentence (25–75)
- ChatGPT, Claude, Gemini & more
- Results in 15 minutes
AI Text Detector — Frequently Asked Questions
AI text detectors analyse perplexity (how predictable word sequences are), burstiness (variation in sentence length and complexity), and token probability distributions. AI models consistently generate text with lower perplexity and lower burstiness than human writers, because they always choose statistically likely words.
The detector works best for English-language text, which is the primary language of training data for the detection model. Accuracy is highest for English academic and professional text.
Light editing — fixing a few words or sentences — typically does not remove the statistical patterns of AI generation. Extensive rewriting can reduce AI scores, but even heavily edited AI text often retains enough patterns to score noticeably above the human baseline.
The detector accepts .docx, .doc, .pdf, .txt, .odt, .rtf and .pages files. Maximum file size is 50 MB or 999 pages.
AI-generated text tends to use formal, comprehensive vocabulary, avoid contractions and colloquialisms, produce evenly structured paragraphs, and favour phrases like "it is important to note", "in conclusion" and "it is worth mentioning". Human writers are more varied, inconsistent and unpredictable in their linguistic choices.
Analyse the Linguistic Fingerprint of Your Text
Find out whether ChatGPT or another AI model generated your text. Upload now and get results in 15 minutes.
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