Is this written by AI?
Find out instantly.
PenProof scans articles, blog posts, and search results as you browse — and gives you a confidence score in seconds. No copy-paste. No tab-switching.
Why PenProof?
Built for speed, privacy, and accuracy.
Instant scanning
Scans pages as you browse. No copy-paste, no manual uploads. Results appear right on the page.
Search result badges
See AI/human scores next to Google and Bing results before you even click. A Pro exclusive.
Privacy-first
Text is analysed and discarded. We never store your browsing history or the content you scan.
Transparent signals
See exactly which patterns triggered: phrase patterns, sentence burstiness, and structural analysis.
Works everywhere
News sites, Medium, Substack, WordPress, Ghost, Reddit — if it has text, PenProof can scan it.
No account needed
Free tier works out of the box. No sign-up, no email, no credit card required to start scanning.
See it in action
Real scores from our detection engine.
How it works
Three steps. Zero friction.
Install
Add PenProof to Chrome from the Web Store. Takes 5 seconds.
Works on Chrome, Edge, Brave, and any Chromium browser.
Browse normally
PenProof automatically scans articles and blog posts as you read them.
Uses requestIdleCallback — zero impact on page load speed.
See the verdict
A small badge appears with a 0–100 score and a clear label: Human, Uncertain, or AI.
Click the badge or extension icon for detailed signals and breakdown.
Simple, honest pricing
Start free. Upgrade when you need more.
Free
- 10 scans per hour
- AI score & label
- Signal breakdown
- Badge on articles
- No search result scanning
Basic
Billed monthly
- Unlimited scans
- Search result badges
- All signals & breakdown
- Email support
Pro
Billed monthly
- Everything in Basic
- Priority support
- API access (coming soon)
- Early feature access
All paid plans include a 7-day money-back guarantee. Cancel anytime.
Questions? Answered.
PenProof uses heuristic analysis (phrase patterns, sentence burstiness, structural signals) to estimate AI likelihood. It works best on articles of 150+ words. No detector is 100% accurate — we show you a confidence score, not a binary yes/no.
Yes. Our pattern library covers common AI writing signatures across all major models. We continuously update our detection heuristics.
Absolutely. Text is sent to our API for scoring and immediately discarded. We do not store article content, and we never track your browsing history.
Chrome, Edge, Brave, and any Chromium-based browser. Firefox support is planned.
Yes. Subscriptions are managed through Lemon Squeezy. Cancel anytime from your billing portal — no questions asked.
A paid feature that shows AI/human score badges directly on Google and Bing search results, so you can evaluate content credibility before clicking.
Stop guessing. Start detecting.
Join thousands of readers who verify content authenticity as they browse.
Add to Chrome — It's free