No AI-written text detection. There is no reliable way to tell whether a person or a model wrote a paragraph, and a tool that claims otherwise is either guessing or selling something. Students have been accused on the strength of such guesses.
No key on our side. Every tool that needs a model calls the provider from your browser with your key, or runs a model locally. If this site held a key, a single viral day would turn into a bill and then into a rate limit, and your text would pass through somebody else's server to get here.
No hosted plagiarism database. Comparing a document against the web is a serious indexing problem, and any free tool that appears to do it is comparing against something much smaller than it implies.