CGI-Bin CGI (Common Gateway Interface) is a specification for the transfer of data between a web server and a CGI program. CGI programs are commonly written in languages such as Java, Perl, C, C++, etc. Common examples of CGI programs include search engines, guestbooks, etc. CGI scripts need to be saved in ASCII format and uploaded to your server's cgi-bin in ASCII or text format. This is very important.