… with the "Generate & Copy" buttons works in Safari only if TLS is used for the connection, i.e. you use the HTTPS URL https://www.jakob-spies.de/….
Click on the "Generate" button to produce random integers in the closed interval between the specified boundaries. The number of random numbers to produce is specified by the value of the field "Count" in this table.
For the random generator to work precisely, these numbers should not have more than, say, 14 digits.
Click on the "Generate" button to produce a random unsigned 64-bit integer in hexadecadic notation ("hexadecimal" is wrong, BTW, as it mixes Greek and Latin).
Click on the "Generate" button to produce a most secure password ("Generate & Copy" copies the new password also to the clipboard). If the radio button "only alphanumeric characters" is chosen, then the password consists of random latin letters and digits, otherwise of arbitrary printable ASCII characters, including or excluding blanks (but no other whitespace characters) according to the chosen radio button. A blank at the start or end of the password is never permitted.
The random generator needs a certain "entropy" for producing really unpredictable random numbers. For collecting this entropy it needs some time.