About Astra AI Detector

Astra is a free, private AI detector that shows you why — not just a number.

Most AI detectors ask you to trust a single percentage from a black box, upload your writing to a server, and pay once you check more than a few times. Astra was built to do the opposite. It runs entirely in your browser, so the text you check is never uploaded or stored; it is completely free with no sign-up and no limits; and it explains every result with a sentence-level breakdown of the signals behind the score. Around that core detector we have grown a small suite of focused detectors and free writing tools, so one honest, private place can cover most of what people actually need when they wonder “is this AI?”

Astra reads text for the statistical fingerprints that machine writing tends to leave behind — chiefly how predictable the word choices are and how uniform the sentence rhythm is — and turns that into a probability score with per-sentence highlights. Because the analysis happens on your own device, you can watch your browser's Network tab and see that nothing is uploaded, and the detector keeps working even if you go offline after the page loads. The full method, in plain language, is on how AI detection works.

Each detector shares the same private, in-browser engine but is tuned and written for a specific question:

• AI Detector — the main, unlimited AI checker with sentence-level analysis for any text.
• ChatGPT Detector — for the latest models: GPT-6 Astra, Sol, GPT-5 and GPT-4o, alongside Claude, Gemini and more.
• AI Content Detector — for publishers, editors and writers checking articles and web copy before they go live.
• AI Humanizer & Paraphrase Detector — catches AI text that has been reworded, paraphrased or run through a “humanizer” to hide it.
• Private AI Detector — the privacy-first framing: nothing uploaded, nothing stored, ideal for confidential drafts.
• Gemini AI Detector — check whether text was written by Google Gemini.
• How Professors Detect AI — how AI detection is used in schools, and why a flag is a signal, not proof.

Alongside the tools, we keep honest, practical guides:

• How AI detection works — perplexity, burstiness and the signals behind a score.
• AI detector accuracy & limits — how accurate detectors really are, and where they fail.
• AI detector vs plagiarism checker — what each one actually catches, and when you need both.
• GPTZero alternative, Turnitin alternative and Originality.ai alternative — honest, side-by-side comparisons for anyone weighing their options.

The same free, private, no-sign-up approach powers a set of everyday writing tools:

• Word Counter — accurate word, character, sentence and reading-time counts.
• AI Rewrite Detector — spot paraphrased or reworded AI and compare text similarity.
• Plagiarism Checker — check for duplicate or copied content.
• English Dictionary — definitions, IPA pronunciation, synonyms and rhymes.
• AI Text Normalizer — strip hidden Unicode, homoglyphs and stray Markdown to clean text.

• Private by design. Detection runs in your browser; your text never reaches our servers.
• Genuinely free. No account, no email, no word limit, no paywall a few checks in.
• Explainable. Every result comes with the sentences and signals behind it, so you can question it.
• Honest. We report a probability, not a verdict, and we are open about the limits.
• Built for real text. The AI-refined signal catches writing that has already been humanized — the kind most detectors miss.

AI detection is probabilistic evidence, not proof of authorship. No detector is 100% accurate: false positives happen — especially with formal or non-native (ESL) English — and heavily edited AI can slip through. Treat any result as one signal, consider context, and never make a decision that affects someone's grade, job or reputation on a score alone. We set this out in full on the accuracy & limits page and in our Terms of Service.

Astra is funded by privacy-respecting analytics and by advertising served by third-party networks — which is what lets everything stay free, unlimited and sign-up-free. Those ads are chosen and served by third parties, not by us, and the text you analyze is never part of any of it. You can read exactly what is collected, and how to opt out, in our Privacy Policy.

For questions, feedback, corrections or press, email hello@astradetector.com. We welcome reports of false positives — they help us describe the limits honestly.