What is htpasswd?
htpasswd is a command-line tool of the open source http server apache httpd, used to generate password files for http basic authentication.
What is the difference between encryption methods?
MD5:Encrypt passwords using MD5. On Windows, Netware and TPF, this is the default encryption method.
crypt: Encrypt passwords using crypt(). On platforms other than Windows, Netware and TPF, this is the default. Although it is supported by htpasswd on all platforms, it is not supported by the httpd server on Windows, Netware and TPF.
SHA: Encrypt passwords using SHA. It is designed for easy import or migration to Netscape using LDAP Directory Interchange Format (ldif).
plain: No encryption, use plain text passwords. Although htpasswd can create such passwords on all platforms, the httpd server only supports plain text passwords on Windows, Netware and TPF.
Why make it online?
If we don't use the apache server, for example using nginx, we may not have this command-line tool at hand and cannot generate password files. With the online version, it is convenient for server administrators to use.