AI Text Detector: Free Online AI Writing Checker

How it works

Paste a paragraph or an entire article into the box above and this tool scores it for patterns that show up disproportionately in AI-generated writing. It does not call out to any AI model or send your text to a server. Instead it runs four independent statistical checks against the words, sentences, and paragraphs you typed, weights them, and combines the result into a single 0-100 score. Four statistical properties are scored and weighted to produce an overall AI likelihood estimate:

• 📚AI vocabulary (35%) — words and phrases AI models use disproportionately often: "delve," "nuanced," "pivotal," "seamlessly," "it's important to note," etc.
• 📏Sentence variation (30%) — humans mix short punchy sentences with longer complex ones. AI output tends to be uniform in length (measured as the coefficient of variation across sentence lengths).
• ✂️Contraction usage (25%) — AI writing is typically formal and avoids contractions ("do not" vs "don't"). Frequent contractions suggest human authorship.
• 📝Paragraph uniformity (10%) — AI often produces paragraphs of very similar length. Requires at least 3 paragraphs to score.

Why these four signals

Each signal targets a habit that large language models pick up during training and rarely shake off without deliberate editing. The vocabulary check flags terms like "delve," "leverage," "underscore," and "it's worth noting" because they appear at a much higher rate in model output than in ordinary human writing, even though none of them are wrong on their own. The sentence variation check looks at burstiness: humans naturally alternate between a short sentence and a long, clause-heavy one, while models tend to settle into a narrow band of sentence lengths and stay there. Contraction usage catches a subtler tell. Models default to a slightly formal register unless prompted otherwise, so "do not" and "cannot" show up far more than "don't" and "can't." Paragraph uniformity closes the loop by checking whether the passage is built from blocks of roughly equal size, a structural habit that shows up in longer AI-generated pieces once you have at least three paragraphs to compare.

Reading your score

The score sits on a 0 to 100 scale, with 0 representing the strongest human signal and 100 the strongest AI signal. Below 25 is labeled "very likely human-written," 25 to 39 "probably human-written," 40 to 54 "unclear — mixed signals," 55 to 74 "possibly AI-generated," and 75 and above "very likely AI-generated." The signal breakdown panel underneath the score shows you exactly which of the four checks pushed the number up or down, so you can see whether a high score came from dense AI vocabulary, flat sentence rhythm, a lack of contractions, or uniform paragraphs, rather than treating the final number as a black box.

Common use cases

Teachers and editors use this tool as a first pass on submitted essays or articles before deciding whether a closer read is warranted. Writers run their own drafts through it after using AI for brainstorming or a first pass, checking whether their editing pulled the sentence rhythm and word choice back toward a natural voice. Content teams screen freelance submissions for flat, generic phrasing before publishing. None of these uses require an account, an upload, or a wait for results since the whole analysis finishes the moment you stop typing.

Getting an accurate reading

Paste at least 200 to 300 words. The detector needs 50 words minimum to run at all, but short passages give the sentence variation and paragraph uniformity signals too little data to be reliable, so scores on very short snippets should be treated as rough at best. Paste full paragraphs rather than bullet fragments or headlines, since the sentence and paragraph checks depend on complete sentences with normal punctuation. If you are comparing two drafts of the same piece, run them back to back and compare the signal breakdown rather than just the headline number, since a five or ten point swing on a short passage can come down to a single long sentence.

What the score can't tell you

This is a heuristic tool, not a trained classifier, and it makes no claim to detect AI text with certainty. A careful human writer with a formal style, few contractions, and evenly paced paragraphs can score high for entirely human reasons. AI text that has been rewritten, restructured, or heavily edited by a person can score low even though a model produced the first draft. Treat the result as one input among several, alongside your own read of the tone, factual claims, and context in which the text was written, rather than as a final verdict on authorship.

Related: Case Converter for text formatting, or JSON Formatter for data cleanup tasks.

Frequently Asked Questions