Free AI Content Detector
Estimate whether 80-1,500 words read as AI-written using browser style signals plus an optional online AI check. Results are estimates, not proof.
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How to estimate whether a text reads as AI-written
Paste 80-1,500 words to get a blended estimate from browser style signals and an optional online AI check, with highlighted sentences and plain explanations.
- Paste 80-1,500 words of English text, up to 12,000 characters, into the Text to check box.
- Leave Also run the online AI check selected for a second opinion, or clear it to keep the text in your browser.
- Select Check text. The browser analysis appears at once; the online check, when used, adds its score a few seconds later.
- Read the estimate label and each signal bar, then review the highlighted sentences and the reasons listed under them.
- Copy the summary if you need a record, and treat the result as one input rather than a final judgment.
When an AI content check is useful
Editors, teachers, content managers and writers sometimes want a quick read on whether a draft has the hallmarks of AI-generated prose. A freelance article that feels oddly generic, a product description that repeats stock phrases, or your own draft that went through an AI assistant can all benefit from a second look at style.
The most practical use is self-review. If your writing is flagged, the highlighted sentences show where it sounds formulaic, such as stacked transitions or filler phrases, and you can revise those lines to sound more like you.
It is not a verdict on honesty. Treat the estimate as a prompt for a conversation or a closer read, never as the only basis for a grade, a rejected submission or an accusation.
Worked example with the built-in sample
Select Load example to paste a 117-word business paragraph set in nine sentences. With the online check turned off, the browser analysis scores it 70 out of 100. Sentence length variation scores 100 because the sentences average 13.0 words with a low variation of 0.21. Common AI phrases scores 100 with seven hits, including plays a crucial role and in conclusion, which is 5.98 per 100 words.
Repeated three-word phrases and vocabulary diversity both score 0 because nothing repeats and the type-token ratio is a high 0.89. Structure and punctuation uniformity scores 75, driven by five sentences that open with transitions such as Furthermore and Moreover. The weighted result is 30 plus 25 plus 15, or 70, which falls in the Likely AI band.
If the online check then returned 80, the final estimate would be 0.4 times 70 plus 0.6 times 80, which is 76. The sample is also marked low confidence because it has fewer than 200 words.
How the estimate is calculated
The browser analysis measures five signals and maps each to 0-100, where higher is more typical of AI text. Sentence length variation carries 30 percent, stock phrases 25 percent, structure and punctuation uniformity 20 percent, repeated three-word phrases 15 percent and vocabulary diversity 10 percent. Diversity uses a moving type-token ratio over 50-word windows so long texts are not penalized.
The optional online check sends the text to a small language model that returns a likelihood from 0 to 100 and a few short signals. When it succeeds, the final estimate weights it at 60 percent and the browser score at 40 percent. Below 35 is labeled Likely human, 35 to 64 Mixed or uncertain, and 65 or more Likely AI.
Common mistakes to avoid
Do not check very short passages. A 90-word paragraph does not contain enough sentences to measure rhythm reliably, so results can flip after small edits.
Do not assume a high score means cheating. Legal writing, academic abstracts, translated text and the work of people writing in a second language are often uniform and formal, which these signals can mistake for AI. AI text that a person has edited can also score as human.
Finally, do not compare scores across different detectors. Each tool uses its own method and scale, so a 70 here and a 40 elsewhere are not contradictory facts about the same text.
Useful tips and limitations
- Check at least 200 words and six sentences; shorter samples are marked low confidence because their scores swing widely.
- If the online check is unavailable or you have used your five daily checks, the browser-only result is still shown with the reason.
- Use the highlighted sentences to revise stock phrases and vary sentence length in your own drafts.
- Keep the online check off for confidential text; the browser analysis still gives a full signal breakdown.
Common questions
Can the AI Content Detector prove that a student or writer used AI?
No. It gives an estimate based on style patterns and can be wrong in both directions. Formal, edited, short or non-native English writing is often flagged by mistake. Do not use it as the only evidence for grades, penalties or decisions about a person.
What happens to my text when the AI Content Detector runs its online check?
When the online check is selected, your text is sent to an online AI service to produce a likelihood score and a few short signals. We do not save the text or results. Clearing the checkbox keeps the analysis entirely in your browser.
Why does the AI Content Detector limit online checks to five per day?
The online check shares a small free daily AI allowance with the site's other AI tools. A per-visitor limit and a tool-wide daily budget keep it available for everyone. The browser analysis has no daily limit.
Which signals does the AI Content Detector measure in the browser?
It measures sentence length variation, common AI phrases, repeated three-word phrases, vocabulary diversity and structure and punctuation uniformity, then combines them with fixed weights into a 0-100 score.
Why does the AI Content Detector mark some results as low confidence?
Samples under 200 words or six sentences do not give stable measurements of rhythm and repetition, so small edits can move the score a lot. Paste a longer passage when possible.
Does the AI Content Detector check plagiarism or name the AI tool used?
No. It only estimates whether the style resembles AI-generated text. It does not compare against other sources or identify a specific model. Use the Text Similarity Checker to compare two texts you already have.
This tool sends requests to the ToolWorld Online service to run its check. No account is needed, and submitted content is not stored or logged.