# Astra AI Detector

> Astra is a free, 100% in-browser (TensorFlow.js) AI-text detector that also flags humanized, paraphrased and manipulated AI writing many detectors miss. No sign-up, unlimited, private by design — your text never leaves your device. Results are a probability, not proof.

Astra's "AI-refined" signal reads meaning and sentence structure, not just word choice, so lightly edited or paraphrased AI text is still caught — as a probability. Astra also ships five free, client-side text tools. Everything runs in the browser and is free.

## Detector
- [AI Detector (home)](https://astradetector.com/): Paste text, get an AI-probability score entirely in your browser.
- [ChatGPT Detector](https://astradetector.com/chatgpt-detector): Detect text written by ChatGPT and GPT models (GPT-6 Astra, Sol, GPT-5, GPT-4o).
- [AI Humanizer & Paraphrase Detector](https://astradetector.com/ai-humanizer-detector): Flags humanized, paraphrased and reworded AI via the AI-refined signal — the kind many detectors miss.
- [AI Content Detector](https://astradetector.com/ai-content-detector): General AI-writing detection for articles and web copy.
- [Private AI Detector](https://astradetector.com/private-ai-detector): Detection with zero uploads — runs fully in-browser.

## Who it's for
- [Gemini AI Detector](https://astradetector.com/gemini-detector): Check whether text was written by Google Gemini.
- [How Professors Detect AI](https://astradetector.com/how-professors-detect-ai): How AI detection is used in schools — probability, not proof.

## How it works & accuracy
- [How AI Detection Works](https://astradetector.com/how-ai-detection-works): Plain-English explanation of perplexity, burstiness and the signals behind a score.
- [AI Detector Accuracy](https://astradetector.com/ai-detector-accuracy): What the score means, false positives, and its limits.

## Comparisons & alternatives
- [AI Detector vs Plagiarism Checker](https://astradetector.com/ai-detector-vs-plagiarism-checker): How the two differ and when to use each.
- [Free GPTZero Alternative](https://astradetector.com/gptzero-alternative): Free, private, no-signup alternative to GPTZero.
- [Free Turnitin Alternative](https://astradetector.com/turnitin-alternative): Free alternative for AI-writing checks you can run yourself.
- [Free Originality.ai Alternative](https://astradetector.com/originality-ai-alternative): Free, no-signup, unlimited alternative.

## Free tools
- [AI Humanizer](https://astradetector.com/ai-humanizer): Rewrites awkward or robotic text so it reads naturally and clearly, keeping the original meaning — a writing-improvement aid, not a way to defeat detectors.
- [Word Counter](https://astradetector.com/tools/word-counter): Word, character, sentence and reading-time counts.
- [AI Rewrite Detector (Text Similarity)](https://astradetector.com/tools/text-similarity): Compare two texts to catch AI rewriting and paraphrase overlap.
- [Plagiarism Checker](https://astradetector.com/tools/plagiarism-checker): Client-side duplicate-content / similarity check.
- [English Dictionary](https://astradetector.com/tools/english-dictionary): Definitions, IPA pronunciation, synonyms and rhymes.
- [AI Text Normalizer](https://astradetector.com/tools/ai-text-normalizer): Strip hidden Unicode, homoglyphs and stray Markdown from text.

## Optional
- [About Astra](https://astradetector.com/about): What Astra is and how it stays free.
- [Privacy](https://astradetector.com/privacy): Client-side by design; your text is never uploaded.
- [Terms](https://astradetector.com/terms): Free, provided as is; results are probabilistic.