Note, however, that the actual value is transmitted to the server as clear text, so password inputs do not provide sufficient security for credit card numbers or other highly sensitive information. Read-only elements are still submitted with the form. Disabled elements are read-only elements with the added restrictions that the values are not submitted with the form, the elements cannot receive focus, and the elements are skipped when navigating the document by tabbing. The radio and checkbox input types provide switches that can be turned on and off by the user. Checkboxes can be checked without changing the state of other checkboxes with the same NAME .
Some browsers require one radio button in a group to be selected at all times.
The file input type creates a field through which users can upload files from their local computer or network. CGI libraries such as CGI.pm allow simple handling of such forms. Form-based file upload is unsupported by many currently deployed browsers. Authors should provide alternative methods of input where possible. Select an HTML document to upload and validate.