AI Detection Tool
Comparing AI detection tools? Start with the one that runs its own trained model instead of renting someone else's — and publishes its real accuracy numbers. DetZero scores text from ChatGPT, GPT-5, Claude, Gemini and DeepSeek, free, with no sign-up and no stored text.
What separates a real detection tool from a demo
Search for an AI detection tool and you will find dozens of pages that look alike. Under the surface they are not alike at all. Five things separate a tool built for the job from a demo with a textarea:
1. Its own model — not an API wrapper
Many “detectors” quietly send your text to a general-purpose AI API and dress up the reply as a score. That is a chatbot's guess, billed as measurement. DetZero's model was trained by us, for this one job, and runs on our server.
2. Your text goes nowhere
A wrapper sends everything you paste to a third party. DetZero scores text in memory on its own server — never written to disk, never logged, never used for training. When the result appears, the text is already gone.
3. Calibrated, not confident-sounding
A score is only useful if you know what it costs to be wrong. Our verdict bands are set at a measured false-flag rate of about 1% on human writing, so “likely AI” is a threshold we can defend, not a colour chosen to look decisive.
4. Published accuracy — failures included
Every tool claims accuracy; few publish the test. Our accuracy page shows the benchmark, the numbers, and the story of the earlier DetZero model we had to retire when honest testing exposed it. If a tool won't show its working, discount its claims.
5. Free without the funnel
No account, no card, no “first paragraph free”. A check costs us almost nothing because the model is ours, so the full score and the full sentence highlighting are simply free.
6. Evidence, not just a number
Every result highlights the sentences that drove the score, so you can judge the evidence yourself instead of trusting a bare percentage — ours or anyone else's.
How DetZero scores text
DetZero is an ensemble: a neural classifier, a text-predictability signal and writing-rhythm features each read the text, two further models examine linguistic patterns — sentence-length variation, punctuation, vocabulary structure — and a small calibrated combiner weighs them into one AI-probability score. It was trained on modern human writing set against output from the current generation of AI systems: ChatGPT and GPT-5, Claude, Gemini and DeepSeek.
On our latest locked benchmark — human texts with natural formatting, matched to the AI texts for length — it catches 82% of AI text at a false-flag rate of about 1% on human text. On topics unlike the benchmark, expect closer to 58%. The full methodology, the per-generator results and the known blind spots are on the accuracy page.
Which checker should you use?
AI Detector
The main DetZero homepage runs this same model — the general-purpose starting point for any text.
ChatGPT Detector
Specifically suspect ChatGPT or GPT-5? That page explains how GPT-5-era writing is caught, and where the limits are.
AI Code Detector
Checking source code, comments or commit messages instead of prose? Use the code page — and read its honest limits first.
Frequently asked questions
What should I look for in an AI detection tool?
Five things: a model of its own rather than a wrapper around a general AI API; a clear promise that your text is not stored; published validation numbers, including the failure cases; thresholds calibrated to a stated false-flag rate; and sentence-level highlighting so a score comes with evidence you can inspect, not just a number.
Is this AI detection tool really free?
Yes. Completely free, no sign-up, no card, and no trial that expires. You can check up to 2,000 words at a time.
Does DetZero send my text to ChatGPT or another AI API to check it?
No. DetZero's model was trained by us and runs on our own server. Your text is scored in memory here and immediately discarded — it never leaves for a third-party AI service.
How accurate is this AI detection tool?
On our latest locked benchmark — naturally formatted human and AI texts matched for length — the current model caught 82% of AI text at a false-flag rate of about 1% on human text. On topics unlike the benchmark, expect closer to 58%. Our accuracy page publishes the full results and limitations.
Do you store the text I check, or use it for training?
Neither. Your text is never written to disk, never logged, and never used to train our models. When the result appears, the text is already gone. See the privacy page.
Can an AI detection tool prove that someone used AI?
No tool can. A score is a probability, not proof of authorship. Use it as one signal among several — drafts, notes and writing history matter more than any single number.