Free AI Detector — Know Instantly If Text Was Written by ChatGPT, Claude, or Gemini
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About this tool
Detect ChatGPT, Claude, and Gemini text in seconds. Get an overall probability score plus sentence-level explanations using our professional-grade neural network analysis. 100% private and secure.
AI-generated content is everywhere — in student essays, blog posts, news articles, job applications, and business reports. Whether you're an educator checking for academic integrity, an editor verifying originality, or an employer screening a cover letter, you need a reliable AI content detector that gives you a clear answer — not just a vague warning.
Plainscan's AI Detector analyzes writing patterns, linguistic structure, sentence predictability, and vocabulary distribution to determine the probability that a piece of text was generated by an AI system such as ChatGPT (GPT-4o / GPT-5), Claude, Google Gemini, Llama, or any other large language model. You get a scored result plus a plain-English explanation of exactly why the content was flagged — not just a number.
Quick Answer: How do I check if text is AI-generated for free?
To check if text is AI-generated for free, simply create a free Plainscan account, paste your text or upload a document (PDF, Word, or TXT), and click "Analyze Text." Our AI detector will provide an overall probability score from 0–100% and highlight specific sentences that exhibit machine-like patterns. Free users get 100 checks per day.
How the Plainscan AI Detector Works
Our AI detection engine combines three analytical layers to deliver accurate, explainable results:
1. Perplexity Analysis
AI language models generate text by predicting the most probable next word or phrase. This makes AI-written content statistically "smooth" — low perplexity — compared to human writing, which tends to include unexpected word choices, regional expressions, and deliberate stylistic decisions. Our engine measures perplexity across the full document to identify machine-like smoothness.
2. Burstiness Detection
Humans write in bursts: short punchy sentences followed by longer elaborate ones. AI systems tend to produce uniform sentence lengths and grammatical structures. Burstiness analysis scores the variance in sentence rhythm — low variance is a strong signal of AI authorship.
3. Pattern & Entity Recognition
Our models are trained on millions of human-written and AI-generated samples across essays, news articles, research papers, creative writing, and business content. They recognize AI-specific vocabulary patterns, filler constructions, and structural tells unique to each major model. The result is a 0–100% probability score with a sentence-level breakdown highlighting the most AI-like sections of your text.
Plainscan AI Detection Plans
| Plan | Daily Docs | Max File Size | AI Features |
|---|---|---|---|
| Free | 100/day | 50 MB | Basic Checks, Ad-supported |
| Pro — $8/mo | Unlimited | Unlimited | Full AI Access, No Ads, Reports |
| Teams — $16/mo | Unlimited | Unlimited | Pro Features + API Access |
Who Uses Plainscan AI Detector?
Educators
Check student essays and theses for academic integrity with probability scores and highlights.
Editors
Verify freelance content authenticity and ensure published work meets human-written standards.
HR Teams
Screen cover letters and applications to ensure candidates genuinely wrote their own materials.
Legal & Compliance
Add a forensic layer to document review and maintain compliance audit trails with PDF reports.
SEO Teams
Audit content libraries to ensure articles align with Google's helpful content guidelines.
Publishers
Protect brand reputation by identifying machine-generated news or creative writing.
How to Use the AI Detector — Step by Step
Create Free Account
Sign up at plainscan.com in under 30 seconds. No credit card required.
Upload or Paste
Paste text directly or upload a PDF, DOCX, or TXT file up to 50 MB.
Analyze Content
Click 'Analyze Text' and our engine returns results in seconds.
Review Probability
See an overall score (0–100%) and sentence-level pattern highlights.
Interpret Results
Read the plain-English explanation of why content was flagged.
Download Report
Pro users can save a formatted PDF report of the detection results.
AI Detection Accuracy — What You Need to Know
No AI detector is 100% accurate. Edited or paraphrased AI text is significantly harder to detect than raw output. Plainscan AI Detector is designed to be used as a supporting signal — not a standalone verdict. Always use the score alongside other contextual factors.
Important: AI detectors can produce false positives, particularly for non-native English speakers. Never use an AI detection score as the sole basis for a high-stakes decision.
Frequently Asked Questions
Everything you need to know about AI detection and content verification.
What is an AI content detector?
An AI content detector is a tool that analyzes text and estimates the probability it was generated by an AI system like ChatGPT, Claude, or Gemini. It works by measuring statistical patterns like perplexity (word choice predictability) and burstiness (sentence rhythm variance).
Do I need to sign up to use the Plainscan AI Detector?
Yes — a free Plainscan account is required to run AI detections. Signing up takes under 30 seconds and requires no credit card. Free accounts include 100 document checks per day.
How accurate is the Plainscan AI Detector?
Our engine is optimized for high accuracy on raw and lightly edited AI-generated content from major models (GPT-4o, GPT-5, Claude, Gemini). Accuracy ranges from 65% to 99%+ depending on the level of human editing.
Can Plainscan detect content from ChatGPT, Claude, and Gemini?
Yes. Plainscan's detection models are trained on outputs from all major LLMs, including ChatGPT (GPT-3.5 through GPT-5), Anthropic's Claude, Google Gemini, and Meta's Llama models.
Can I upload a PDF or Word document for analysis?
Yes. Plainscan accepts direct text input as well as file uploads in PDF, DOCX, and TXT formats. Free users can upload files up to 50 MB; Pro users have unlimited file size.
What is the minimum text length required for analysis?
The minimum required input is 50 characters. For the most reliable results, we recommend analyzing at least 300 characters (roughly 50–60 words).
Will Google penalize AI-generated content?
Google rewards content that demonstrates first-hand expertise and value, regardless of how it was produced. However, low-quality, mass-produced AI content that lacks depth is at risk of ranking downgrade.
Are there false positives in AI detection?
Yes — all AI detectors can produce false positives. Non-native English speakers and formal academic writers are more likely to be incorrectly flagged. Always use scores as one signal among several.
Can I download my detection report as a PDF?
Yes — Pro and Teams users can download a formatted PDF report of each detection, including the overall score, probability breakdown, and sentence-level highlights.