The utilities on this site are built as JavaScript that runs on your own device. Text you type, files you drop in, and the results they produce are processed locally. That content is not uploaded, logged, or stored on a server. Close the tab and it's gone.
There's no sign-up and no user database. The site doesn't set advertising or cross-site tracking cookies. A standard session cookie may be used for basic site function, nothing more.
A couple of tools genuinely need a network request to do their job:
Like most websites, the server may record standard request information (such as timing and error data) to keep the site healthy and fast. This is aggregate operational telemetry, not a profile of you.
If anything here is unclear, get in touch. The site is open source, so you can also read exactly what it does on GitHub.