Editing Common Gateway Interface (section)

{{Short description|Interface between Web servers and external programs}}

{{More citations needed|date=August 2023}}

[[file:Common Gateway Interface logo.svg|thumb|The official CGI logo from the spec announcement]]

In [[computing]], '''Common Gateway Interface''' ('''CGI''') is an interface specification that enables [[web server]]s to execute an external program to process [[HTTP]] or [[HTTPS]] user requests.

Such programs are often written in a [[scripting language]] and are commonly referred to as ''CGI scripts'', but they may include [[compiler|compiled]] programs.{{ref RFC|3875|section=1.4}}

A typical use case occurs when a web user submits a [[web form]] on a web page that uses CGI. The form's data is sent to the web server within a [[HTTP request]] with a [[URL]] denoting a CGI script. The web server then launches the CGI script in a new [[computer process]], passing the form data to it. The CGI script passes its output, usually in the form of [[HTML]], to the Web server, and the server relays it back to the browser as its [[HTTP response|response]] to the browser's request.{{ref RFC|3875}}

Developed in the early 1990s, CGI was the earliest common method available that allowed a web page to be interactive. Due to a necessity to run CGI scripts in a separate process every time the request comes in from a client, various alternatives were developed.