Free AI Detector. Built by the People Who Beat Them.
Paste your text and get an instant human score. StealthGPT's AI detector is trained on billions of human and AI sentences, tuned for GPT-4, GPT-4o, Claude, Gemini, Llama, and every major model. Know exactly how your content reads before you submit it.
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The AI Detector Built by the Humanizing Experts
Most AI detectors are built by companies trying to catch AI content. StealthGPT's detector is built by the company that bypasses those detectors for a living.
That distinction matters. To beat AI detection consistently, you have to understand exactly how it works: what signals detectors look for, how they weight sentence-level patterns, what perplexity and burstiness scores actually measure, and where the models fail. StealthGPT has reverse-engineered every major detector to build a humanizer that consistently achieves a 99% bypass rate. That same understanding is what powers this detector.
The result is an AI checker that tells you not just whether content is flagged, but how human it actually reads, scored on the same criteria the tools you're worried about use.
How the StealthGPT AI Detector Works
Industry-Leading Accuracy
The detector is trained on billions of human-written and AI-generated sentences, giving it a reliable signal across writing styles, subject areas, and content types. It doesn't just pattern-match on surface features. It evaluates the statistical properties of your text the same way professional-grade AI detectors do.
Instant Human Score
Paste your text and get a human score in seconds. The score reflects how naturally human your writing reads on the criteria that matter: sentence variety, vocabulary authenticity, structural unpredictability, and the subtle rhythmic patterns that distinguish genuine prose from machine output. No waiting, no account required for a standard scan.
Works on Any Content Type
Essays, research papers, blog posts, email drafts, social media captions, cover letters: the detector evaluates any written content and returns a reliable human score regardless of subject matter or format.
How Do AI Detectors Work?
Understanding what AI detectors look for is the first step to knowing whether your content will pass.
AI detectors analyze text for statistical patterns that correlate with machine generation. The two most important measures are perplexity and burstiness.
Perplexity measures how predictable or surprising the word choices in a piece of text are. Human writers make unexpected vocabulary choices, take tonal detours, and phrase things in ways that slightly deviate from the most probable next word. AI models tend toward high-probability completions, producing text that's fluent but statistically predictable. Low perplexity scores are a strong signal of AI generation.
Burstiness measures variation in sentence length and complexity across a passage. Human writing naturally alternates between short punchy sentences and longer, more complex ones. AI models tend to produce consistent sentence lengths across paragraphs, a pattern that detectors specifically look for. Low burstiness is another reliable AI signal.
Beyond those two measures, detectors also analyze vocabulary range, transitional phrasing patterns, heading structure, and overall coherence. Content that scores well on all of these reads like a human wrote it. Content that scores poorly on any of them gets flagged.
StealthGPT's humanizer is trained to address all of these signals simultaneously, which is why it achieves a 99% bypass rate across every major detector. The AI detector tool gives you the score before you submit, so you know exactly where you stand.
Who Uses the StealthGPT AI Detector
Students
Check essays, research papers, and assignments before submission to avoid AI flags from Turnitin, GPTZero, and other detectors used by schools and universities.
Content Marketers
Content marketers and SEO writers use it to verify that AI-assisted blog posts and articles will pass the detection tools publishers and platforms increasingly use before accepting content.
SEO Writers
SEO writers use it to ensure that AI-assisted blog posts and articles will pass AI detection tools that platforms are increasingly using before ranking content.
Academics
Scan research papers, manuscripts, and grant proposals to ensure your writing reads as human-authored on the same criteria journals and committees evaluate.
Educators
Evaluate student submissions and your own teaching materials with a detector tuned for the statistical signals that institutional AI policies rely on.
Freelancers
Confirm that deliverables, drafts, and client copy read as fully human before sending, protecting your reputation and meeting AI-free requirements.
Free AI Detector vs. Enhanced Scan
Standard Scan (Free)
The standard scan evaluates up to 200 words and returns a human score immediately. No account required. Ideal for checking short passages, email drafts, social posts, or individual paragraphs before submission.
Enhanced Scan (Account Required)
The enhanced scan runs a deeper analysis using StealthGPT's full detection model, supporting longer documents and returning a more detailed breakdown of where AI patterns appear in your text. Identify specific paragraphs or sentences that are pulling the score down and target them for humanization. Available with a free StealthGPT account.
Unlimited Scanning
Free accounts unlock unlimited standard scans, document uploads, and access to the full StealthGPT suite including the AI humanizer, Stealth Writer, and SEO Writer. One account covers everything.
What to Do If Your Content Flags as AI
A low human score means the content contains detectable AI patterns. The most reliable fix isn't manual editing. It's humanization.
StealthGPT's AI humanizer is built specifically to address the signals that cause AI content to flag. It rewrites content to introduce natural sentence variation, authentic vocabulary, and the structural unpredictability that detectors treat as human. Unlike manual editing, which tends to preserve the underlying AI structure even when individual words change, the humanizer operates at the model level to produce output that reads as genuinely human.
The workflow is straightforward: run a scan, see your score, paste flagged content into the humanizer, and rescan. Most content reaches a passing human score in one humanization pass.
How to Pass AI Detection
Passing AI detection consistently comes down to one thing: making your content read the way human writing actually reads, not just changing enough words that a surface-level check doesn't catch it.
Manual paraphrasing changes vocabulary but usually preserves the AI sentence structure underneath. That structure is what detectors measure. You can swap every third word and still score poorly if the underlying rhythm and phrasing patterns remain the same.
Effective AI detection bypass requires addressing the statistical properties of the text itself: perplexity, burstiness, vocabulary distribution, and transitional phrasing. StealthGPT's humanizer handles all of these automatically, which is why it maintains a 99% bypass rate across Turnitin, GPTZero, Originality.ai, Copyleaks, and every other major detector.
The AI detector tool shows you the score before and after so you can verify the result rather than guess.
Free AI Detector for Essays and Academic Content
The most common use case for AI detection tools is academic: students checking papers before submission, instructors evaluating student work, and institutions managing AI policy compliance.
StealthGPT's free AI detector for essays is calibrated for academic writing specifically. It evaluates the longer, more complex sentence structures typical of research papers and essays, accounts for the higher perplexity expected in academic vocabulary, and returns a score that reflects how Turnitin and similar tools will evaluate the content.
For students, the workflow is: generate or draft your content, run it through the free detector, humanize any sections that score low, and rescan before submitting. The free account covers all three steps.
Frequently Asked Questions
Know Your Score. Then Fix It.
Run a free scan on any text. If your human score is low, StealthGPT's humanizer can fix it in seconds.