# Free AI Detector — GPT-6, Claude & Gemini Free, explainable AI detector for GPT-6, GPT-5, ChatGPT, Claude and Gemini. A 0-100 score with the machine-written lines marked — nothing stored. - Source: https://scanforai.com/ - ScanForAI — AI-writing detection. A score is a signal, not a verdict. --- # Was this written by AI? **Free AI detector and AI checker.** See how much of any text reads as unedited AI — from **ChatGPT, Claude, Gemini** or Copilot — with the signals behind the score in plain English. Up to **20,000 characters** free, no account. ★★★★★ 4.6 from 1142 user ratings Elevated what an editor's pass catches In today's rapidly evolving landscape, it is a testament to human ingenuity that we continue to delve into the rich tapestry of innovation. I tried making sourdough this weekend — total disaster, flour everywhere, but worth it. reads human - **50,000**-character scans - **Deep** scanning — the accurate read - Saved scan **history** - **Batch** file checks ## We measure the text. We don't guess. Most detectors hand you one number and hide the reasoning. ScanForAI shows its working — the specific patterns it read, and how each one moved the score. "In today's rapidly evolving landscape…" sentence rhythmphrasingpredictabilitystructure Reliable signals count more; short text makes checks abstain instead of guess. The AI-leaning lines light up right in your text, with the reasons. ### Sentence rhythm People vary short and long; machines stay even. We measure the burst. ### Vocabulary AI reaches for the same words — “delve”, “tapestry”, “a testament to”. ### Phrasing & tells Contractions, asides, the “it's not just X, it's Y” tic — dozens of signals. ### Predictability How “obvious” each next word is — the machine's own fingerprint. ### See it sentence by sentence. Marked like an editor's pass, not a verdict — the heavier the mark, the denser that line's AI-style wording. A mark doesn't mean the line was written by AI; it means that phrasing shows up more often in AI writing than in human writing. Unmarked means nothing stood out, which is not the same as a clean bill. ## See which parts read AI — not just a single number. Paste a whole draft and ScanForAI marks the AI-leaning lines right in your text, and splits a part-human, part-AI document into sections. It won't claim "Gemini wrote this" — no honest detector can name the model — but it shows you exactly where the machine writing sits. In today's rapidly evolving landscape, it is a testament to human ingenuity that we continue to delve into the rich tapestry of innovation. I finally tried making sourdough this weekend. Total disaster — flour everywhere, and the loaf came out like a brick. Worth it though. The recipe was straightforward to follow, and overall the process was quite rewarding despite the initial challenges I encountered. ## An explainable AI checker for the people a wrong result hurts. Detection is a signal, not a verdict — so we built it to be argued with, not just trusted. ### [For teachers](https://scanforai.com/for-teachers) Screen a class set, see the evidence, and start a conversation — with non-native writers protected, not flagged blind. ### [For students](https://scanforai.com/for-students) Check your own essay before you submit it, see exactly which lines read machine-written, and fix them while they are still yours to fix. ### [vs GPTZero](https://scanforai.com/compare-gptzero) How ScanForAI compares to GPTZero — free to use, with the full per-signal breakdown behind every score. ### [vs Originality.ai](https://scanforai.com/compare-originality) A free, explainable alternative to Originality.ai — no credits, no card, and the reasoning shown in plain English. ## Tuned for the models people actually paste. Every model has habits. These guides show what each one sounds like, what gives it away, and how the scanner marks it — with honest notes on what's hard to catch. ### [Detect ChatGPT](https://scanforai.com/detect-chatgpt) The most-pasted voice on the internet: stock phrases, tidy scaffolding, and how GPT-4/5/6-era text gets caught. ### [Detect Claude](https://scanforai.com/detect-claude) The hardest mainstream voice to catch — and the habits that still give it away. ### [Detect Gemini](https://scanforai.com/detect-gemini) The "Help me write" case: Gemini paragraphs inside human drafts, scored part by part. ### [Writing in a second language?](https://scanforai.com/esl-writers) Non-native writing trips every detector. How ScanForAI adjusts for it instead of flagging blind. Limits at a glance: up to 20,000 characters free, 50,000 with a free account — [the enforced numbers, per plan](https://scanforai.com/pricing). ## One scanner, a whole toolkit. Every tool here answers the same question — was this made by a machine, and what is the evidence? Start free and anonymous. A free account unlocks the full breakdown, deep scan, history and more — no card, ever. ### AI detector Paste any text, get a score and the AI-leaning lines highlighted in place. ### Full breakdown See *which* patterns drove the score, sentence by sentence, so you can judge the evidence instead of a number. ### Deep scan Far more checking on the same text: slower, clearly more accurate, and much less likely to flag human writing. Use it when the answer matters. ### Image AI check Read what an image *declares* about how it was made — Content Credentials, IPTC source type, camera and software tags. A disclosure is proof; its absence proves nothing. ### Injection scan Read an image the way a model would and score the hidden instructions planted in it — including the layers no viewer shows you. ### Batch scan Drop a set of files, pasted essays or URLs and score them all at once. ### History & PDF report Save scans, compare drafts, and export a shareable PDF report. ### Browser extension Check any page or Google Doc as you write, right from your browser — on Chrome, Edge and Firefox. ## Common questions about AI detection. Paste the text above (or upload a file / drop in a URL) and press Scan — you get a 0–100 AI score, the lines that read machine-written marked in place, and the reasons in plain English. Checking for AI is free, instant, and anonymous scans are never stored. **20,000 characters** (about 3,500 words) anonymously, and **50,000 characters** (about 8,500 words) with a free account — that's a full paper or long article in one scan, where many AI checkers cap you around 5,000 characters. Bigger limits come with paid tiers. The 0–100 number says how strongly the text shows the measurable signs of machine writing — even sentence rhythm, stock phrasing, predictable word choice. Low means it reads human, high means it reads like unedited AI. It's a signal with evidence attached, never proof of who wrote it. [How to read the score →](https://scanforai.com/docs/interpreting-scores.html) Yes. The AI detector, the sentence heat-map and the per-signal breakdown are free, and anonymous scans are never stored. Yes — it's tuned against current models including GPT-6, GPT-5, ChatGPT, Claude and Gemini. Deep scan runs considerably more checking, for the most accurate read. It's built for the models people actually paste from — **ChatGPT (GPT-4, GPT-5 and GPT-6)**, **Claude**, **Gemini**, **Microsoft Copilot**, **Llama**, **DeepSeek**, **Grok**, **Mistral** and **Qwen** — plus paraphrased and lightly-edited AI. It reads the statistical habits shared across large language models rather than one vendor's fingerprint, so newer models are usually caught too. No detector is perfect, which is why we always show the signals behind the score. No detector — ours or anyone's — is 100% accurate. ScanForAI returns a signal, not a verdict: a score plus the patterns behind it, so you judge the evidence. Formal and non-native human writing scores higher on every detector. We test against non-native writing specifically and show the reasoning, so a high score starts a conversation, not an accusation. Anonymous scans are never stored. Signed-in scans are saved only for your history and can be deleted anytime. It reads the statistical fingerprints of machine writing: even sentence rhythm, stock phrasing, formal register, and how predictable each next word is. ScanForAI weighs dozens of these patterns and, on deep scan, checks far more of them and far more carefully — then shows you which ones fired, not just a number. Often, yes — schools run detectors, and unedited ChatGPT text carries measurable habits. But detectors are wrong both ways, so a flag is not proof. Check your own work first: paste it here, see what reads machine-written, and if you're wrongly flagged you'll have the evidence to discuss it. Stay calm and bring evidence, not just denial: your draft history, notes, and a ScanForAI report showing the per-line breakdown. Ask which detector was used and its known false-positive rate. No single score is proof — most institutions know that, and the per-signal breakdown turns an accusation into a conversation. Light grammar fixes usually don't move the score much — they clean surface errors without changing your rhythm or word choice. Heavy AI rewriting does. Our score reflects how machine-written the text reads, so lightly-corrected human writing stays low. Today the detector reads English only. Text in another language is not scored yet — the scanner tells you so, in that language, rather than guessing. It will be, once other supported languages are officially released: more are in the works, and each one ships only when it detects as reliably as English does, so we don't promise dates or names before they're ready. Yes — that's the common real case. ScanForAI scores each part on its own and marks the AI-leaning passages in place, so you see exactly which sections read machine-written instead of one blurred average for the whole document. Honestly: good, and getting better — but no detector is a lie detector. Formal and non-native human writing can score high anywhere, and lightly-edited AI can score low. That's why we show the evidence behind every score and frame it as a signal, not a verdict. Treat it as one input, never as proof about a person.