Statistical AI Writing Analysis

Free AI Content Detector for Students

Instantly check whether your essay, dissertation, or thesis contains AI-generated writing patterns before you submit — free, private, and no registration required.

4-signal pattern analysis Sentence-level highlighting Your text is never stored Runs entirely in your browser

Free — no word limit with free account

0 / 500 words · 0 characters

⚠ Over 500 words. Sign in free to analyse documents of any length.

🔒 100% Private: Your document is analysed entirely in your browser — never sent to our servers, stored, or shared with anyone.

AI Content Likelihood Analysing…

0% AI signals

Calculating…

Signal Breakdown — What Was Detected

Sentence Uniformity0%

AI text tends to produce sentences of very similar length. High uniformity = more AI-like.

Vocabulary Repetition0%

AI often reuses words more than human writers. Lower vocabulary variety = more AI-like.

AI Transition Phrases0%

Words like "furthermore", "moreover", "it is important to note" are heavily favoured by AI models.

Sentence Start Patterns0%

AI often begins sentences with the same word types. Low variety in sentence starts is an AI indicator.

Sentence-Level Analysis

AI writing pattern detected Human-like writing

How this score is calculated: We measure four statistical signals — sentence length variance, vocabulary type-token ratio, AI transition phrase density, and sentence-start diversity. Each is weighted and combined into an overall likelihood score. No AI detector is 100% accurate. Formal academic writing naturally scores higher due to structured phrasing. Use this as a guide to identify passages worth reviewing — not as a definitive verdict.

How the Detection Works

Four independent statistical signals are measured and combined into a single likelihood score.

Paste Your Text

Paste any academic text — a dissertation chapter, essay, or assignment. No registration needed for up to 500 words.

Statistical Analysis

Our algorithm measures sentence length patterns, vocabulary richness, transition phrase density, and structural uniformity.

Signal Breakdown

Each of the four signals is scored individually, so you can see exactly which aspect of your writing looks most AI-like.

Review & Revise

Purple-highlighted sentences show where AI patterns were detected. Revise those sections before submission.

The Four Detection Signals

Each signal targets a different statistical property of AI-generated text.

📏

Sentence Uniformity

35% weight

Human writers naturally vary sentence length — mixing short punchy sentences with longer, complex ones. AI models tend to produce sentences that cluster around a consistent length. We measure the standard deviation of sentence lengths: low variance is a strong AI indicator.

📚

Vocabulary Richness

25% weight

The Type-Token Ratio (TTR) measures how many unique words appear relative to total words. Human writing on technical topics tends to have higher vocabulary diversity. AI models frequently reuse the same vocabulary, producing a lower TTR than comparable human text.

🔗

AI Transition Phrases

25% weight

Phrases like "furthermore", "moreover", "it is important to note", "in conclusion", and "as a result" appear far more frequently in AI-generated text than in natural human academic writing. We count the density of 12 known AI-preferred transition patterns.

🔤

Sentence Start Patterns

15% weight

Human writers instinctively vary how they begin sentences — with "The", "This", "However", "While", "In", etc. — creating natural variety. AI models tend to gravitate toward certain opener patterns and repeat them throughout a piece, reducing starter variety.

How to Read Your Score

What each range means and what to do about it.

0 – 20%

Low likelihood. Your writing shows strong statistical indicators of human authorship — good sentence variety, rich vocabulary, and low filler phrase use. You can submit with confidence.

21 – 40%

Some patterns detected. A few AI-like writing patterns were found — this may reflect formal academic style rather than AI authorship. Review the highlighted sentences and consider adding more varied phrasing.

41 – 65%

Significant indicators. Multiple AI writing patterns identified. These sections may be flagged by Turnitin's AI detection. Rewrite purple-highlighted passages in your own voice before submission.

66 – 100%

High likelihood. Substantial AI writing patterns throughout the document. This is likely to be detected by institutional AI tools. Significant rewriting is strongly recommended before submission.

ℹ️ Scores are estimates based on statistical patterns. Highly structured formal academic writing may score higher than expected, even when entirely human-written. Always review individual highlighted sentences rather than relying solely on the overall score.

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Frequently Asked Questions

Yes — completely free for documents up to 500 words, with no registration required. Create a free account to check documents of any length. There is no paid tier for this tool.

No. All analysis runs entirely inside your browser using JavaScript. Your text is never transmitted to our servers, stored, or shared with any third party. It disappears the moment you close the page.

The statistical approach is effective at identifying common AI writing patterns, but no detector — including institutional tools — is 100% accurate. Highly formal academic writing can produce elevated scores even when entirely human-written. Use this to identify sentences worth reviewing, not as a definitive verdict. Always read the individual signal breakdown alongside the overall score.

Yes — Turnitin launched its AI Writing Detection feature in April 2023. It is now active at the majority of UK universities and claims to detect content generated by ChatGPT, GPT-4, and similar models with over 98% confidence at a document level. Many institutions have introduced specific academic misconduct policies for AI-generated content. Always check your university's current policy before submitting.

Formal academic writing shares some statistical properties with AI output — structured argumentation, consistent sentence rhythm, and academic transition phrases are all natural features of well-written essays. If your score is elevated but you wrote the work yourself, review the purple-highlighted passages and add more varied sentence structures, personal analysis, and discipline-specific vocabulary. If you used AI to assist with any part of the writing, those sections are likely to score highest.

Yes, with a free account. The 500-word limit applies to unregistered use only. Once you sign in or register (free), you can paste and check documents of any length. For a full dissertation, we recommend checking each chapter separately to get more granular feedback on which sections score highest.