# QuillBotAI Pro — Free AI Text Detector & SynthID Watermark Scanner

> Free, unlimited AI content detection tool with sentence-level perplexity scoring, burstiness variance analysis, and Google SynthID watermark verification. No signup. No data retention. GDPR & CCPA compliant.

QuillBotAI Pro is a free, browser-based AI text detector. It identifies AI-generated content from GPT-4o, GPT-5, Claude, Gemini, Llama, Mistral, and humanizer-altered text. It also detects Google SynthID watermarks in images and videos. All processing runs in volatile memory — zero data retention, no accounts required.

## Docs

- [AI Text Detector](https://www.quillbotai.pro/): Paste any text to receive a sentence-level AI confidence heatmap, perplexity score, and burstiness variance.
- [ChatGPT Detector](https://www.quillbotai.pro/detect/chatgpt): Detection tuned for GPT-4o and GPT-5 output patterns.
- [Gemini Detector](https://www.quillbotai.pro/detect/gemini): Detection tuned for Google Gemini output patterns.
- [Claude Detector](https://www.quillbotai.pro/detect/claude): Detection tuned for Anthropic Claude output patterns.
- [Humanizer Bypass Detector](https://www.quillbotai.pro/detect/humanizer-bypass): Screens text that has been paraphrased or run through humanizer tools.
- [AI Writing Detector](https://www.quillbotai.pro/ai-writing-detector): Guide and tool for checking articles, blog posts, and web copy.
- [Academic Integrity](https://www.quillbotai.pro/academic-integrity): AI detection guidance for educators and students.
- [SynthID Watermark Detector](https://www.quillbotai.pro/synthid-checker): Upload images (JPEG, PNG, WebP) or videos (MP4, WebM) up to 22 MB to check for Google SynthID watermarks.
- [Blog](https://www.quillbotai.pro/blog): Articles on AI detection methods, accuracy limits, and tool comparisons.
- [About & Methodology](https://www.quillbotai.pro/about): Who builds the tool, how detection works, and its documented limitations. Author: Zoe Parker, founder and detection researcher.
- [Sitemap](https://www.quillbotai.pro/sitemap.xml): Full sitemap of all pages.

## API

- [AI Detection Endpoint](https://www.quillbotai.pro/api/detect): POST JSON with a `text` field. Returns `overallAIScore`, `overallHumanScore`, per-sentence scores with alerts, perplexity/burstiness metrics, and a humanized version.
- [SynthID Detection Endpoint](https://www.quillbotai.pro/api/detect-synthid): POST JSON with `media` (base64), `mimeType`, and `filename`. Returns `isWatermarked`, `confidenceScore`, source model, and forensic breakdown.

## Detection Capabilities

- Supported languages: English (EN-US, EN-GB, EN-CA, EN-AU), Urdu (Nastaliq), Roman Urdu, Hindi, Spanish, French, German, Portuguese.
- Detection vectors: word predictability (perplexity), sentence-length variation (burstiness), vocabulary diversity, and model-specific phrasing patterns.
- Output is a per-sentence confidence heatmap, not a pass/fail verdict.
- Known limitations: no AI detector is 100% accurate. Confidence drops on short texts (under ~50 words), heavily edited text, and text run through paraphrasers or humanizers. Results are evidence to weigh, not proof of authorship.
- Detection is fairest on clean, unedited AI output. Non-native English writing can produce false positives on any detector, including this one.

## Privacy

- Zero-retention: all text and media processed in volatile memory, purged immediately after analysis.
- No logs, no databases, no training data collection.
- Fully GDPR and CCPA compliant.

## Optional

- [robots.txt](https://www.quillbotai.pro/robots.txt): Crawler access rules.
- [Privacy Policy](https://www.quillbotai.pro/privacy): Full privacy and data handling policy.