Is this AI‑generated?

The software looks at things in your writing that you would never notice yourself, like how easy each word would have been for a language model to guess and how even the rhythm of your sentences is, and then it holds what it found up against big piles of writing where the author of each piece was already known (a person or a model). No detector “knows” who wrote your text, since all it can give you is an estimate of how likely it was. What we did at Cobalynx was take that estimate, test it against what had really happened, and print our error rates next to it, so you can see how often we got it wrong. Every step is laid out on the methodology page.

You can trust them as one piece of evidence, and we would never let one of them stand in for proof. In 2023 a team led by Weber-Wulff put 14 of the popular ones to the test, and not one of them got to 80% accuracy in the conditions they tried. People have pasted the U.S. Constitution into them and been told it was written by a machine. What Cobalynx did differently was put its own error rates out in the open, on the evidence page, so that when you get a verdict from it you will also know how much weight it can take. There is a longer version of this answer in our guide to how accurate detectors really are.

A false positive is when a person wrote something and the software said a machine wrote it, and of all the mistakes this kind of software can make it is the one that does the most damage to the writer. Cobalynx’s false-positive rates are on the evidence page, with the raw counts and the confidence intervals for each confidence band, and we set the thresholds so that a confident wrong accusation will stay as close to zero as we could get it.

Not reliably, and that goes for every one of them and not only ours. Once you get below 150 words or so there is not enough in the text for a detector to say much about it, so Cobalynx will ask you for a minimum length and will not guess. If what you have is a chat message, a single review or a short email, then what we would do is put several of them together (or paste in the whole transcript) and run that as one text.

There is no straight answer to that, and we would be careful with somebody who gave you one. How well a detector does depends on how long the text was, what language it was in, which model wrote it and how much a person edited it afterwards, and most of the “most accurate” rankings you will find were put out by the vendors grading their own product. The question worth asking instead is if the vendor has published error rates that a third party could go and reproduce, and if it said what threshold it ran them at. Cobalynx’s are public, with the raw counts and the confidence intervals, on the evidence page, and our list of questions for a detector’s maker is on the why-cobalynx page.

False positives are real, and they land most often on the kind of writing your teacher asked you for. If your structure was formal, if you ran it through a grammar tool, or if English is not your first language, all of that looks, to the software, like what it was trained to catch, and a flag from it is a hint that a person should look closer. Save your version history and your drafts first, since they are far stronger evidence than a score, and then read our step-by-step guide for people who were falsely accused.

No. Your text and files are processed in memory and deleted the moment your verdict is delivered — never stored, never used for training, never shared. If load queues your scan, your text is held in memory only while it waits its turn, and once it has been scored the text is gone before you have even got your verdict back. Say you closed the tab and never came back for your result. In that case it is purged by a background timer within five minutes, even if nobody else ever visits. The one thing that is held on to for that short while is the verdict itself, which is the score and the band it falls in, never your words. There is an automated test that proves all of this on every release, so you do not have to take our word for any of it. The privacy page has the whole story, including the little that a website still touches, which in this case is anonymized connection logs, and no cookies and no third-party trackers at all.

Yes. It is free, there is no account to make, and there is no word count that you have to pay to get past. You paste in your text or you drop in a file, and you get your result. The things it cannot do are short text, guessing from the pixels of a picture, and proving that a person wrote something, and we would rather you knew that before you relied on it.