Free Grammarly AI Checker Alternative

Schools and teachers use tools like Turnitin, GPTZero and the Grammarly AI checker (often called the Grammarly AI detector) to flag AI-written work. The problem: these checkers sometimes flag text that a student wrote entirely by themselves. Detectize lets you run the same kind of check on your own work first, see which sentences look AI-like, and revise them before you hand anything in.

Many students search for the Grammarly AI detector because they want to know how their essay will look to an AI checker before a teacher sees it. Detectize does the same kind of check, independently and for free. Paste up to 1,500 words, and you get an overall AI probability plus a highlight on every sentence, so you can see exactly which lines read as machine-like instead of guessing from a single number.

There is no sign-up and no word-count trial. Your text is checked and then discarded: we don't store it, and we never send it to a school or plagiarism database.

Different detectors are trained differently, so they often disagree on the same text. A low score here doesn't guarantee a low score in another tool, and a high score isn't proof of anything. The most useful way to use any checker is as an early warning: find the sentences that sound generic, rewrite them in your own words with specific details, and keep your drafts so you can show how your work was made.

Less accurate than their scores make them look. Every AI detector, including this one, gives you a probability, not a verdict. Even good ones make mistakes in both directions: they miss some AI-written text, and they flag some text that a person wrote.

We didn't want to just repeat that warning, so we ran a small test of our own. We checked 29 passages of known origin through the detection engine behind this tool: 15 written by people and 14 written by an AI assistant. It flagged 13 of the 14 AI passages as likely AI. It also flagged 6 of the 15 human passages. The human passages it got wrong were mostly modern, plain-language writing, such as public-health and science pages from U.S. government websites. Older literary prose was almost never flagged.

This is a small sample, not a benchmark, and we only tested one detection engine. It does not tell you how often a false flag will happen to your own work. It does show that clear, neutral, well-organized writing, which is exactly what students are taught to produce, can be flagged as AI.

AI detectors don't know who wrote a text. They estimate how predictable the wording is. Language models tend to choose likely words in a smooth, even rhythm, so text that is predictable, evenly paced and full of standard phrasing scores as more AI-like. A careful explanation of a technical topic often looks like that, whether a person or a model wrote it.

That is why the same detector can give one paragraph of a report 1% and the next paragraph 99%. The score reflects how the sentences read, not where they came from.

Treat the score as a second opinion, not a judgment. Look at which sentences are highlighted and ask whether they sound generic: stock transitions, vague claims, or sentences that could appear in any essay on the topic. Replacing them with specific examples, your own observations and your own way of explaining things usually helps, and it makes the writing better anyway.

Keep your drafts and version history while you work. If someone ever questions your writing, the record of how it was made is stronger evidence than any detector score, in either direction.