Free AI detector to detect AI content
Paste any text and instantly find out if it was written by a human or generated by ChatGPT, GPT-4, Gemini or Claude. A fast, accurate, free AI detector — no login, no word limits, no catch.
AI detection returns a probability estimate — use it as a strong signal, not absolute proof. Your text is never stored.
What does it mean to detect AI content?
To detect AI content means analyzing a piece of writing and estimating how likely it was produced by an AI language model rather than a person. As tools like ChatGPT, GPT-4 and Claude make it effortless to generate essays, articles and emails, telling human writing apart from AI writing has become genuinely hard. Detect AI is a free AI detector built to close that gap in seconds.
Unlike a plagiarism scanner, an AI detector doesn't compare your text against a database of sources. Instead, it studies the statistical fingerprints of the writing itself — how predictable each word is, how sentences are structured, and how much natural variation the text contains. Human writing tends to be less predictable and more varied; AI-generated text is usually smoother and more uniform. Our model reads those patterns and turns them into a single, clear AI probability score.
Whether you need to detect ChatGPT in student submissions, keep your blog authentic and Google-friendly, or simply check whether a message was written by a bot, Detect AI gives you a clear percentage and highlights the exact sentences that look AI-generated.
How to detect AI writing
Detect AI content in any text in seconds — no account, nothing to install.
Paste your text
Drop in an essay, article, email or any writing you want to run through the AI detector.
Run the AI detector
Detect AI scores how likely each sentence was generated by ChatGPT, GPT-4, Claude or another model.
Read your result
See the overall AI percentage instantly, with every sentence highlighted by how likely it is to be AI-written.
Check your own draft before someone else does
A growing number of schools, publications and employers run submissions through an AI checker. If you wrote something yourself but it leans on tidy, predictable phrasing, it can still be flagged. Running your draft through Detect AI first shows you exactly which sentences read as machine-written, so you can rework them in your own voice before you hand anything in.
The sentence highlighting is the useful part. A single percentage tells you there is a problem; the highlighted lines tell you where. Most writers only need to vary a few sentence openings, cut a stock transition or two, and add a specific detail for the score to drop sharply.
What your AI score actually means
The percentage is the estimated share of the text that reads as AI-generated. Here is how to interpret each range.
Reads as human
Natural variation in sentence length, specific details, personal phrasing. Nothing to act on.
Mixed or polished
Typical of human writing edited with a grammar tool, or an AI draft that was substantially rewritten. Check the highlighted sentences.
Likely AI-assisted
Most of the text follows the predictable patterns of a language model. Expect several highlighted sentences in a row.
Reads as AI-generated
Uniform rhythm, generic transitions and very low perplexity throughout. Strong signal — still confirm with context before acting on it.
How Detect AI compares
A free, unlimited AI detector with sentence-level highlighting — the features other detectors put behind a sign-up or paywall.
| Feature | Detect AI | ZeroGPT | Other detectors |
|---|---|---|---|
| 100% free & unlimited | ✓ | Capped | Paywall |
| No sign-up required | ✓ | Optional | ✕ |
| No word or character limit | ✓ | Capped | Capped |
| Sentence-level highlighting | ✓ | ✓ | ✕ |
| Detects GPT-4o, Claude & Gemini | ✓ | ✓ | Partial |
| Works in 40+ languages | ✓ | ✓ | ✕ |
| Text never stored | ✓ | Varies | Varies |
| Free API access | ✓ | Paid | ✕ |
Comparison reflects typical free tiers and can change over time. Detect AI is free with no account and no limits.
Who uses Detect AI
From classrooms to newsrooms — anyone who needs to tell human writing from AI writing.
Teachers & educators
Screen student essays and assignments for ChatGPT and other AI before grading.
Students
Make sure your own writing reads as human and won't be falsely flagged by an AI checker.
Writers & bloggers
Keep your content authentic and protect your search rankings from AI-flagged text.
Editors & publishers
Quickly check freelance and guest submissions with a reliable AI detector.
SEO & marketing
Verify that outsourced articles are genuinely written, not mass-produced by AI.
Recruiters & HR
Spot AI-written cover letters and applications during hiring.
A first-pass signal, not a verdict
Teachers and editors use Detect AI as a quick screen: paste a submission, read the score, and look at which sentences are highlighted. When a whole essay lights up red and the writing has no personal detail, that is worth a conversation. When only a paragraph is flagged, it often just means the student polished that section with a grammar tool.
No AI detector can prove how a text was produced, and we say so plainly. Pair the result with what you already know about the writer — their previous work, their voice in class, whether they can explain their argument — before drawing any conclusion.
Everything you need to check, fix and clean AI text
Detect AI is one of three free tools that work together. Check a text, rewrite it in a human voice, or remove the invisible characters AI tools leave behind — no account for any of them.
AI Humanizer
Rewrite AI-sounding text so it reads naturally. Choose a reading level, purpose and strength, then see the before-and-after AI score.
Open tool →🧹AI Watermark Remover
Find and delete zero-width characters, hidden Unicode tags and odd spaces that AI tools embed in copied text. Runs entirely in your browser.
Open tool →🤖ChatGPT Detector
A detector page tuned for ChatGPT output — the tells of GPT-4o and GPT-5 writing, and how to read the result.
Open tool →Why use Detect AI
Instant results
Get an AI probability score and sentence-level highlights in about two seconds.
Free & unlimited
No sign-up, no credit card, no word caps. Detect AI as often as you like.
Detects every major model
Works on ChatGPT, GPT-4, GPT-4o, Gemini, Claude, Llama, DeepSeek and more.
Sentence highlighting
See exactly which sentences look AI-generated — not just a single number.
40+ languages
Detect AI content across many languages, not only English.
Private by design
Your text is used only to run the check and is never stored or shared.
What makes Detect AI different
Most AI detectors either hide the good features behind a paywall or hand you a single mysterious number. Detect AI is completely free and shows its work: alongside the overall AI score, it highlights each sentence so you can see precisely where the AI writing is concentrated.
It's also built for real-world text. Writing is rarely 100% human or 100% AI — people edit ChatGPT drafts, and AI tools rephrase human notes. Instead of a black-and-white pass or fail, Detect AI gives you a nuanced percentage plus sentence-level detail, so mixed documents are handled honestly. And with no login and no limit, you can check as much text as you need.
Tips for accurate AI detection
Why human writing sometimes gets flagged
False positives are the main weakness of every AI detector, including ours. Formal, formulaic writing — lab reports, legal boilerplate, technical documentation, text written in a second language — is naturally predictable, and predictability is exactly what detectors measure. Very short samples are also unreliable because there is simply not enough text to analyze.
If your own writing is flagged, the fix is usually small. Vary sentence length on purpose, replace generic transitions such as furthermore and in conclusion with plain connectors, and add a concrete example or a first-person observation. The highlighted sentences show you where to start. Our AI humanizer can do a first pass automatically.
For anyone evaluating other people's writing: never let a score be the only evidence. Ask for drafts, ask the writer to explain a passage, and compare it with their earlier work. A detector is a signal to look closer, not a judge.
Perplexity, burstiness and the fingerprints of machine writing
Language models choose the most statistically likely next word, so the text they produce is unusually predictable. Detect AI measures that predictability — called perplexity — across the passage. It also measures burstiness: how much sentence length and rhythm vary. People write in bursts, mixing a four-word sentence with a forty-word one; models tend to keep everything evenly medium.
Those two signals, combined with vocabulary and structure cues, produce the percentage you see. Longer passages give the model more evidence, which is why we recommend at least fifty words and a full paragraph rather than an isolated sentence.
Detecting ChatGPT, Gemini, Claude and the rest
Each model family has a recognizable style. ChatGPT and GPT-4o favor balanced three-part lists, confident summaries and transitional phrases such as "additionally" and "overall". Gemini output often opens with a restatement of the question and leans on bulleted structure. Claude writes in longer, more hedged sentences with careful qualifiers. Llama, Mistral and DeepSeek produce text that is closer to GPT-style output, with somewhat more repetition.
Detect AI does not try to name the model — it estimates whether the writing is machine-generated at all, which is the question most people actually need answered. The statistical signals above are shared across model families, so a text generated by a newer model is still caught by the same predictability and rhythm analysis. If you specifically need to screen for ChatGPT, the ChatGPT detector page walks through its particular tells.
AI detection terms, explained
Perplexity
How surprised a language model is by each word. Low perplexity means the text is highly predictable — a hallmark of machine writing.
Burstiness
The variation in sentence length and complexity across a passage. Human writing is bursty; AI output tends to be flat and even.
False positive
Human-written text that a detector labels as AI. Most common with formal, templated or non-native writing.
Humanizing
Rewriting AI-generated text so it reads naturally — varied rhythm, concrete detail, fewer stock phrases.
AI watermark
Invisible Unicode characters (zero-width spaces, tag characters, unusual spaces) that some tools embed in text so copies can be traced.
Sentence-level highlighting
Marking the individual sentences that drive the AI score, rather than returning a single number for the whole text.
A free ChatGPT detector and AI checker in your browser
Detect AI is a free AI content detector that tells you whether a piece of writing was more likely produced by a human or by a large language model. Paste any paragraph, essay, article, or email and our AI checker returns an instant probability score — no account, no credit card, and no per-day cap. Because everything runs through a lightweight web app, you can detect AI writing from your laptop or phone in seconds.
Under the hood, our ChatGPT detector studies the same statistical fingerprints that separate machine text from human text: perplexity (how predictable each word is) and burstiness (how much sentence length and rhythm vary). Text from ChatGPT, GPT-4o, Gemini, and Claude tends to be smooth and low-perplexity, while genuine human writing is burstier and less predictable. Combining these signals lets the detector flag AI-generated content with useful confidence.
Teachers use it to screen essays, editors and SEO teams use it to keep content authentic, and writers use it to double-check their own drafts before publishing. It is popular with students who want to confirm that paraphrased notes still read as their own work, and with recruiters reviewing cover letters. Whatever the use case, the AI detector stays free and unlimited — that is the whole point.
Detection is only half of the picture. If a draft of your own keeps getting flagged, our free AI humanizer rewrites it in a more natural voice, and the AI watermark remover strips the invisible Unicode characters that some AI tools hide in copied text. To learn more about how the technology works, our accuracy philosophy, and why the tool is free, read the about page. AI detection is probabilistic, so always treat a score as a strong signal rather than absolute proof.
Detect AI — frequently asked questions
Is Detect AI really free?
Yes — Detect AI is 100% free with no sign-up, no login and no usage limits. Check as much text as you want, as often as you want.
How accurate is the AI detector?
It gives a reliable probability estimate for most text, but no AI detector is perfect. Treat the score as strong guidance rather than absolute proof, especially for short passages or heavily edited writing.
Which AI models can it detect?
Detect AI recognizes text from ChatGPT (GPT-3.5), GPT-4, GPT-4o, Gemini, Claude, Llama, DeepSeek, Mistral and most other large language models.
How is Detect AI different from ZeroGPT?
Detect AI offers the same core detection — an AI percentage with sentence-level highlighting — completely free, with no sign-up and no word limit. Many alternatives cap free usage or gate features behind a paid plan.
Can it detect ChatGPT and GPT-4o?
Yes. Detect AI is tuned to catch the newer, more natural output from GPT-4 and GPT-4o, not just older models — and it flags the specific sentences that read as AI.
Does it work on paraphrased or humanized AI text?
Often, yes. Rewriting AI text lowers the score, so heavily humanized content may land in the middle range — the sentence highlights still help you see which parts read as AI.
Can teachers use it to check student work?
Yes, many teachers use Detect AI as a first-pass AI detector. Because no detector is 100% accurate, use the result as one signal alongside your own judgment before making a decision.
Does Detect AI work in other languages?
Yes. It detects AI-written content across 40+ languages, not only English.
How is this different from a plagiarism checker?
A plagiarism checker compares your text to existing sources to find copied passages. Detect AI instead analyzes the writing style itself to estimate whether it was generated by AI — two different problems.
Do you store the text I check?
No. Your text is only processed to return your result and is never saved or shared.
Can I use Detect AI to check my own writing before submitting it?
Yes, and it is one of the most common uses. Paste your draft, look at the highlighted sentences, and rework the ones that read as generic or overly uniform. Re-run the check until you are happy with the result.
What is the difference between the AI detector and the AI humanizer?
The detector tells you how AI-like a text reads. The humanizer rewrites a text so it reads more naturally and then scores it again, showing the before-and-after AI percentage. They are meant to be used together.
Why does the score change when I run the same text twice?
Small variations are normal: the model's estimate has a margin of error, and tiny edits — a comma, a line break — can shift sentence boundaries. Large swings on identical text are rare; if you see them, check that the full passage was pasted.
Does Detect AI detect AI-generated images or code?
No. Detect AI analyzes written prose only. Source code, tables of numbers and images are outside what the model is trained on and will not return a meaningful score.