Claude AI Detector
Detect Claude Sonnet 5, Opus 5, and Haiku generated text with sentence-level precision. Our advanced detection engine analyzes Anthropic's unique burstiness patterns, hedging language, and rhetorical structure in real time.
How Claude Detection Works
Three simple steps to detect Claude-generated content.
Paste Your Text
Paste your text or upload a document. We support PDF, DOCX, and TXT formats for Claude detection.
AI Analyzes for Claude Patterns
Our multi-model detection engine analyzes every sentence for Claude-specific writing patterns and statistical signatures.
Get Sentence-Level Results
Receive a detailed report with per-sentence confidence scores, highlighting exactly which portions are AI-generated.
Why Use a Dedicated Claude Detector?
Anthropic's Claude models have rapidly become some of the most capable AI writing assistants, known for nuanced, balanced, and articulate outputs. Plagly.ai's Claude Detector is specifically calibrated to recognize the linguistic fingerprints of Claude Sonnet 5, Opus 5, and Haiku 4.5, as well as previous Claude 3.5 models. Claude exhibits characteristic epistemic hedging, unprompted both-sides synthesis, and higher burstiness than GPT-family models. Our multi-layer detection engine evaluates token-probability distributions, sentence rhythm dynamics, and rhetorical pacing to distinguish Claude-generated text from human writing. Whether verifying academic papers, marketing copy, or technical analyses, Plagly provides transparent sentence-by-sentence confidence scores without storing your documents.
Learn more about our technologyAnthropic Claude (Sonnet 5, Opus 5 & Haiku 4.5)
Plagly's detection engine is specifically calibrated for Anthropic Claude (Sonnet 5, Opus 5 & Haiku 4.5), using multi-layer analysis to identify this model's unique writing fingerprint.
Key Features
Everything you need to detect Claude content with confidence.
Sonnet 5 & Opus 5 Detection
Calibrated for Anthropic's newest Claude Sonnet 5, Opus 5, and Haiku 4.5 models, identifying subtle linguistic signatures that generic detectors miss.
Sentence-Level Analysis
Every sentence receives an individual AI probability score, making it easy to spot Claude-written passages in mixed documents.
Burstiness & Rhythm Scoring
Evaluates dynamic sentence-length variation and pacing to accurately distinguish Claude's natural cadence from human writing.
Multi-Format Support
Upload PDFs, DOCX files, or paste text directly. All formats are processed with the same high accuracy.
Privacy Protected
Your content is analyzed in real time without storage. We never retain your documents or train on your data.
Free to Use
Quick scans are free with no registration. Detect Claude content instantly.
How to Spot Claude Writing
Common tells that a passage was generated by Anthropic Claude (Sonnet 5, Opus 5 & Haiku 4.5):
- Careful epistemic hedging: "it is worth noting," "that said," "in many contexts," "while X, it is also true that Y."
- Unprompted both-sides synthesis: balances opposing arguments before formulating a measured middle stance.
- Scaffolded formatting: consistent bolded lead-in bullet categories, parallel list structures, and closing recaps.
- Measured, articulate register that avoids dogmatic overclaiming or emotional exaggeration.
- Dynamic sentence-length burstiness paired with characteristic qualifier-first introductory clauses.
What Claude Sonnet 5 and Opus 5 text actually looks like
Claude's fingerprint is less about robotic vocabulary than rhetorical posture. While newer models like Sonnet 5 and Opus 5 write with unprecedented natural fluency, they still maintain Anthropic's signature training habits: cautious hedging, balanced neutrality, and disciplined structure. These are the patterns our detector analyzes on this page, and the ones you can evaluate yourself.
Persistent hedging and cautious framing
Phrases like “it’s worth noting”, “that said”, “in many contexts”, and “while X, it’s also true that Y” appear at a much higher frequency than in human writing. Claude is trained to avoid overclaiming, and that caution surfaces as a steady rhythm of qualifiers throughout an article.
Unprompted both-sides synthesis
Asked for a direct stance, Claude Sonnet 5 frequently returns a balanced synthesis instead: the argument for, the argument against, and a measured middle ground. Human opinion pieces usually commit early and spend their length championing that position.
Scaffolding applied by default
Subheadings, numbered sequences, and a closing synthesis frequently appear even when answering simple prompts. If a 300-word response arrives neatly segmented with multiple subheadings and an introductory recap, that structure is a meaningful indicator.
The bolded lead-in bullet pattern
A bolded one- or two-word category label, followed by a colon, followed by an explanation sentence — repeated with parallel grammatical symmetry down an entire list. Human lists are typically more spontaneous and varied in syntax.
Calibrated burstiness across paragraphs
Claude Sonnet 5 and Opus 5 vary sentence lengths more naturally than models that march along at an invariant cadence. While this makes Claude harder for basic perplexity filters to flag, our detector couples token probability tracking with structural discourse analysis to identify Claude's specific rhythm.
None of these traits is definitive proof on its own — careful human writers frequently structure their work with precision. That is why Plagly displays the exact sentences behind each detection score rather than an unsubstantiated percentage.
Plagly vs Other Claude Detectors
See how Plagly.ai compares for detecting Claude-generated content.
| Feature | Plagly.ai | GPTZero | Turnitin |
|---|---|---|---|
| Claude Detection | Partial | ||
| Sentence-Level Analysis | Limited | ||
| Free Quick Scans | Limited | — | |
| No Signup Required | — | — | |
| Multi-Model Detection | |||
| Confidence Scores | Limited | ||
| Document Upload | |||
| Privacy (No Storage) | — | — |
Frequently Asked Questions
Common questions about detecting Claude-generated content.
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