GUID Essentials runs entirely on your device. It has no server to send anything to, no accounts, no analytics, no cookies and no third-party code. The only requests it makes are for its own files; nothing you type, open or generate is ever part of one.
What you type, open or generate is processed in the app itself and never uploaded. The page lists exactly what is kept on your device — usually nothing more than a preference or two — and what clearing your browser data removes.