This tool runs only in your browser. It makes no network call, it sends nothing anywhere, and it does not save your password. Copy it, use it on your own machine, and keep it private.
Longer passwords are harder to guess. Use at least 16 characters for a WiFi password if your machine allows it.
Safety note: After you generate a password, change it on your own machine through its admin panel, test it as a customer, and do not share it publicly, do not write it on the machine, and do not reuse it for other accounts. If you lose it, use your own machine recovery steps, not a public support page.