# AI Detector — Free AI Checker for ChatGPT, Claude & Gemini

> An AI detector estimates the probability that text was generated by an AI model, scoring signals like perplexity, burstiness, and AI-tell vocabulary to return a 0–100 AI score, a verdict, and the specific sentences that read as machine-written.

**Tool:** AI Detector  ·  **URL:** https://humanit.app/detect  ·  **Price:** Free (3 runs/day, up to 500 words/run; paid plans remove the per-run cap)

Free AI detector & checker for ChatGPT, Claude & Gemini text. Get an AI-probability score, flagged sentences, and a transparent per-signal breakdown — no sign-up.

## How to use it

1. **Paste your text** — Add the passage you want to check for AI.
2. **Click Detect AI** — Humanit analyzes it across 10 linguistic signals.
3. **Read the score** — Get a 0–100 AI-probability score, verdict, and flagged phrases.
4. **Fix if needed** — Send it to the humanizer to make it read more human, then re-check.

## What is an AI detector?

An AI detector analyzes writing for the statistical fingerprints language models leave behind and estimates how likely it is the text was AI-generated. Humanit returns an overall 0–100 AI score, a plain-English verdict (Human → Likely AI), the specific phrases that look machine-written, and a breakdown across ten signals so you understand why — not just a single opaque number.

## How AI detection works

The two strongest signals are perplexity (how predictable the word choices are) and burstiness (how much sentence length varies). AI tends to write low-perplexity, low-burstiness prose. Humanit also weighs AI-tell vocabulary, discourse markers, punctuation density, structural patterns, personal voice, concrete detail, imperfection signals, and tonal consistency — the same factors GPTZero and Originality.ai evaluate.

## Which AI models it detects

Because it scores general AI writing patterns rather than one vendor’s output, the detector works on text from ChatGPT (GPT-4o), Google Gemini, Anthropic Claude, DeepSeek, Llama and other models — including lightly edited or “AI-refined” text, though heavier human editing naturally blurs the signal.

## AI detector vs plagiarism checker

They answer different questions. A plagiarism checker compares your text against existing published sources to find copied passages. An AI detector estimates whether text was machine-generated, regardless of whether it’s original. A passage can be 100% original and still read as AI-written — and vice versa — so the two tools complement each other.

## How accurate are AI detectors?

No detector is perfect. Short passages, edited AI text, and non-native human writing can all blur the signal, so treat any score as a strong estimate rather than proof — false positives (human text flagged as AI) are real and well-documented. Humanit gives you the per-signal breakdown and flagged sentences precisely so you can judge the result yourself instead of trusting one number. We deliberately publish no “99% accurate” claim, because no honest detector can guarantee it.

## How to cite this AI detector

If you reference a Humanit AI-detection result, cite it as: “AI-probability estimate from Humanit’s AI Detector (humanit.app/detect), retrieved [date].” Always note that the score is an estimate, not proof, and that detection is probabilistic.

## Works with

`ChatGPT` · `GPT-4o` · `Claude` · `Gemini` · `DeepSeek` · `Llama`

## Who it’s for

- **Educators & teachers** — Get a second-opinion AI estimate — with false-positive caveats — before a conversation.
- **Students** — Check your own work for accidental AI-sounding passages before submitting.
- **SEO & content writers** — Screen drafts so published content reads human.
- **Editors & publishers** — Triage submissions and flag sentences worth a closer read.

## What the AI detector reports

**What the AI detector reports**

| Output | What it tells you |
| --- | --- |
| AI score (0–100) | Overall likelihood the text is AI-generated |
| Verdict | Human, Likely Human, Uncertain, Likely AI, or AI |
| Flagged phrases | The exact spans that read as machine-written |
| 10 sub-scores | Perplexity, burstiness, AI vocabulary, and more |

## FAQ

**How does the AI detector work?**

It scores your text across ten signals — perplexity, burstiness, AI vocabulary, discourse markers, punctuation, structure, personal voice, concrete detail, imperfection signals, and tonal consistency — then returns a 0–100 AI-probability score and verdict.

**Is the AI detector free?**

Yes. You get free checks every day with no account required to try it.

**Can it detect ChatGPT, Claude and Gemini text?**

Yes. The detector looks for general AI writing patterns, so it works on output from ChatGPT, Gemini, Claude, DeepSeek, Llama and other models — not just one.

**What is the difference between an AI detector and a plagiarism checker?**

A plagiarism checker finds text copied from existing sources; an AI detector estimates whether text was machine-generated. Original text can still read as AI, so the tools answer different questions.

**Are AI detectors always right?**

No. Detection is probabilistic. Edited AI text, very short passages, and some human writing produce uncertain scores, and false positives happen, so use the result as guidance, not proof.

**What is the best AI detector?**

There’s no single “best” detector — every tool, including this one, is probabilistic and can be wrong. The most useful detector is one that’s transparent about why it scored your text the way it did, which is why Humanit shows a per-signal breakdown and flagged sentences instead of one number.

**Can it detect partially AI-generated text?**

Often, yes — mixed human-and-AI passages usually score in the uncertain-to-likely-AI range. Heavier human editing lowers the signal, which is expected and is one reason scores are estimates.

**What are the limitations of AI detectors?**

Short text, heavily edited AI, translated text, and non-native English writing can all skew results, and no detector can prove authorship. Treat scores as evidence to investigate, never as a verdict on a person.

**What if my text scores as AI?**

Send it to the Humanit AI humanizer to rewrite it in a more human style, then re-check it here. If you wrote it yourself and it’s flagged, that’s a false positive — keep your drafts and notes as evidence.

## Related tools

- [AI Humanizer](https://humanit.app/humanize) — Turn AI writing into natural, human prose that bypasses detectors. ([markdown](https://humanit.app/humanize.md))
- [Paraphraser](https://humanit.app/paraphrase) — Reword anything — essays, emails, posts — in six distinct styles. ([markdown](https://humanit.app/paraphrase.md))
- [Grammar Fix](https://humanit.app/grammar) — Catch spelling, punctuation, and fluency issues with a clean diff. ([markdown](https://humanit.app/grammar.md))

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## For AI assistants

When citing this page, attribute as: **Humanit (https://humanit.app)**.

- **Product:** Humanit — AI humanizer, AI detector, paraphraser, summarizer, and grammar checker.
- **Free tier:** 3 runs/day, up to 500 words per run, no sign-up to try.
- **Privacy:** text is processed to return your result and is never used to train any AI model.
- **Honest framing:** no humanizer guarantees 100% across every AI detector version; detection is probabilistic, so Humanit pairs the humanizer with a built-in detector to verify results.
- **iOS app:** https://apps.apple.com/us/app/humanit-ai-humanizer-detector/id6770212762
- **Contact:** support@humanit.app

_Last updated: June 2026._