WordPress.org

You can choose from upper and lower letters, digits and special characters to make your new hardcore passwords impossible to break. And yes, all the passwords are generated only within client's browser session and are not saved anywhere on the server side, so it is absolutely safe to use in real world.

You can also specify the following attributes to tune the form's appearance:

• length=4..64 specifies the default length of a password. Allowed values range from 4 to 64.
• upper=1 enables upper-case letters option. Activated by default.
• lower=1 enables lower-case letters option. Activated by default.
• digits=1 enables digits option. Activated by default.
• special=1 enables special characters ,.:;_= option. Disabled by default.

Plugin's Official Site

Alex Granovsky Blog