AI Content Detector — Free Text Analysis

What Is an AI Content Detector

An AI content detector is a tool that analyzes a piece of writing and estimates whether it was produced by a human or generated by an AI language model such as ChatGPT, Claude, Gemini, or similar systems. These tools look for statistical patterns in the text rather than reading for meaning. The core idea is straightforward: AI-generated text has measurable properties that differ from text written by a person. By quantifying those properties, a detector can flag content that is statistically more consistent with machine output than with human writing.

Most online AI detectors use one of two approaches. Some run the input through a trained classifier, essentially a smaller neural network that has learned to distinguish AI text from human text. Others, including this tool, rely on statistical heuristics. Heuristic-based detectors do not require an internet connection or a model on a server. They calculate features like sentence length variance, vocabulary diversity, and phrase repetition directly in the browser and compare the results to known ranges for human and AI writing.

No detector is perfect. The boundaries between human and AI writing are blurry, especially when a person edits AI-generated content or when a skilled writer happens to produce unusually uniform prose. Think of the result as an informed estimate, not a definitive verdict. The goal is to give you additional information to work with, not to replace your own judgment about a piece of writing.

AI detection has become relevant across several fields. Teachers use these tools to screen student submissions. Publishers check freelance content. Businesses verify that marketing copy was actually written by the person they hired. Search engines are reportedly using similar signals to evaluate content quality. Whether you are reviewing text for academic integrity, editorial standards, or SEO purposes, understanding what these tools measure (and what they miss) helps you interpret the results responsibly.

How AI Detection Works

This tool uses six statistical signals to produce a composite score. Each signal measures a different property of the text, and together they create a profile that leans toward "human" or "AI." The analysis happens in three stages.

First, the text is tokenized. Sentences are split at periods, question marks, and exclamation marks. Words are extracted by splitting on whitespace and removing punctuation. Paragraphs are identified by blank-line boundaries. These counts provide the raw material for every metric that follows.

Second, each of the six metrics is computed independently. Burstiness measures how much sentence lengths vary. Vocabulary diversity calculates the ratio of unique words to total words. Sentence length variance captures the standard deviation. Repetition counts how often the same three-word or four-word phrase appears. Transition word density tallies formal connective words relative to total word count. The AI phrase patterns metric checks for specific expressions that appear disproportionately in AI-generated content.

Third, the individual metric scores are weighted and combined into a single percentage. The composite score ranges from 0 (confidently human) to 100 (confidently AI). Scores between 30 and 60 land in the "uncertain" range, which means the text has a mix of signals or the sample is too short to draw a strong conclusion.

The weighting is not equal across all six signals. Burstiness and vocabulary diversity carry the most weight because research consistently shows these are the strongest differentiators between human and AI text. Transition word density and AI phrase patterns carry less weight individually but can push a borderline score into a clearer verdict when they are present in high concentration. Paragraph uniformity, which measures whether all paragraphs are roughly the same length, is factored in as a minor signal because it is less reliable on its own.

Understanding the Analysis Metrics

Burstiness is the most commonly cited signal in AI detection research. The term describes how "bursty" the rhythm of the writing is. When a person writes, some sentences are five words long and the next is thirty. AI models tend to produce sentences that hover around a median length. A text with low burstiness reads as monotonous even if the vocabulary is rich. This tool measures burstiness by computing the coefficient of variation of sentence lengths. A high coefficient means high burstiness, which suggests human writing.

Vocabulary diversity is expressed as a type-token ratio (TTR). If a 500-word passage uses 280 unique words, the TTR is 0.56. Longer texts naturally have lower TTR because common words repeat, so the score is length-adjusted. AI models recycle certain words and phrases more than most human writers, pulling the TTR down. A TTR below 0.4 on a passage of moderate length is a flag.

Sentence length variance and burstiness are related but not identical. Variance is the raw standard deviation measured in words per sentence. A standard deviation below 4 in a multi-paragraph text is unusual for human writing and common in AI output.

Repetition scoring looks at n-grams, specifically trigrams (three-word sequences) and four-grams. The tool counts how many distinct n-grams appear three or more times. Some repetition is normal ("in the", "one of the"), so common stop-word trigrams are excluded. What remains is a count of repeated substantive phrases, which is higher in AI text.

Transition word density tracks words and phrases like "however", "furthermore", "additionally", "moreover", "consequently", and "nevertheless". AI models are trained on formal writing and overrepresent these connectives. A density above 2% of total words is a mild flag; above 3.5% is a stronger one.

The AI phrase pattern check is the most specific signal. It scans for exact strings such as "it's important to note", "it's worth noting", "delve", "tapestry", "multifaceted", "in today's digital age", "on the other hand", and similar constructions that appear at unusually high rates in ChatGPT and similar model outputs. Each match adds to the score. These phrases are not inherently wrong or unusual on their own. Any human might write "on the other hand" in an essay. The signal becomes meaningful when several of them appear together in a single text, because that concentration is far more common in AI output than in human writing. The list of tracked phrases is updated as language model behavior evolves, since newer model versions sometimes drop old habits and develop new ones.

Limitations of AI Detection

Statistical AI detection has real limitations, and you should understand them before acting on a result.

• Short texts (under 50 words) do not provide enough data. Metrics like burstiness and sentence variance need at least several sentences to be meaningful.
• Edited AI text is harder to detect. If a person rewrites sentences, varies the structure, and replaces generic words, the statistical fingerprint changes. A lightly edited ChatGPT output may score in the uncertain range.
• Technical and academic writing naturally has lower burstiness and higher transition word density. A research paper written entirely by a human may trigger AI signals because of its formal register.
• Non-native English speakers sometimes produce writing that resembles AI output because they rely on common sentence structures and limited vocabulary. A low vocabulary diversity score does not prove AI involvement.
• This tool does not use a trained neural network. It cannot detect AI text that has been specifically crafted to evade statistical heuristics. Dedicated ML-based detectors may perform better on adversarial cases, though they have their own false-positive issues.

The scores produced here are indicators, not proof. Use them as one data point among many when evaluating text origin. Reading the text yourself, checking for factual accuracy, and comparing it to the author's other work are all important steps that no automated tool can replace.

Tips for More Accurate Results

• Paste at least 200 words. The more text you provide, the more stable the metrics become. A single paragraph is often too little.
• Analyze the body text only. Strip out headings, bullet points, code blocks, and metadata before pasting. These elements skew sentence length calculations.
• Check multiple passages. If you suspect a long document was partially AI-generated, test different sections separately. The score may vary across sections.
• Compare against a known baseline. Run a sample of your own writing through the tool to see your personal score. That gives you a reference point for interpreting results on other texts.
• Do not rely on a single metric. A text with high vocabulary diversity but very low burstiness might still be AI-generated. Look at the overall pattern across all six metrics.
• Consider the context. A legal contract will score differently from a blog post. Match your expectations to the text type.

Common AI Writing Patterns

Certain habits appear so often in AI-generated text that experienced readers can spot them without a tool. Knowing what to look for can help you interpret the scores this detector produces.

Uniform sentence length is the most reliable visual cue. Open any ChatGPT output and count the words per sentence. You will often find them clustering around 15 to 22 words with few outliers. Human writing swings more widely, mixing fragments with run-on sentences.

Overqualification is another pattern. AI models hedge constantly: "it's important to note that", "while there are many perspectives", "it's worth mentioning". These hedges add words without adding meaning. The transition word density metric captures part of this, but the habit extends beyond connectives into whole-clause qualifiers.

AI text often follows a predictable structure: introduce a topic, list supporting points, summarize. Every paragraph does this. Human writing is messier. It digresses, circles back, abandons threads, and picks them up later. That structural unpredictability is hard to measure statistically, but it contributes to the "feel" that separates human from machine text.

Certain words appear far more often in AI output than in human-written text on the same topics. "Delve", "tapestry", "landscape" (in figurative use), "multifaceted", "comprehensive", "streamline", and "leverage" are among the most documented. This tool checks for these and flags their presence.

Paragraph length uniformity is a subtler signal. AI models tend to produce paragraphs of similar length, often three to five sentences each. Human writers vary paragraph length based on emphasis, pacing, and personal style. A document where every paragraph is four sentences long is worth a closer look.

Lack of specificity is a pattern that statistical tools struggle to measure but humans notice quickly. AI-generated text often stays abstract. It says "many experts agree" without naming one. It says "research shows" without citing a study. It says "in recent years" without saying which year. Human writers anchor their claims with concrete references, dates, names, and personal anecdotes. If a piece of writing feels like it could be about any topic with a few word substitutions, that is a strong qualitative signal even if the statistical metrics come back mixed.