Common Gateway Interface

Definition of Common Gateway Interface

Common Gateway Interface (CGI) is a standard protocol that allows web servers to interact with external programs, typically to process user data submitted through forms or to create dynamic web content. These external programs, called CGI scripts, are often written in programming languages like Perl, Python, or C. CGI acts as a gateway, bridging the gap between web servers and server-side applications, enabling seamless communication and data transfer.


The phonetics of the keyword “Common Gateway Interface” can be represented as:KOM-uhn GATE-way IN-ter-feys

Key Takeaways

  1. Common Gateway Interface (CGI) is a standard protocol for web servers to execute server-side scripts or programs, and to generate dynamic web content.
  2. CGI scripts can be written in a variety of programming languages like Perl, Python, and PHP, providing flexibility for web developers to create dynamic websites and applications.
  3. Although still in use, CGI has been largely replaced by newer, more efficient technologies such as FastCGI, server scripting languages like PHP, and web frameworks like Django and Ruby on Rails that offer better performance and scalability.

Importance of Common Gateway Interface

The Common Gateway Interface, or CGI, is an important technology term because it serves as a crucial standard that enables web servers to generate dynamic content, facilitating smooth communication between web servers and software applications.

CGI allows web applications to run on various platforms and languages, paving the way for interactive websites where users can input data and receive customized information in return.

This functionality enhances user experience, broadens the scope of web development by increasing versatility, and has led to the widespread proliferation of web services and data-driven websites.


The Common Gateway Interface, or CGI, serves the crucial purpose of enabling web servers to generate dynamic content, crafted specifically for each user request. This technology acts as a medium to connect external applications with web servers, empowering them to communicate with one another, and thereby bringing forth tailored and interactive web content.

From simple forms and guest books to complex applications including online banking, CGI has played a pivotal role in laying the foundation for dynamic web experiences, enhancing the internet’s usability and functionality. Using the CGI protocol, web developers can employ various programming languages, such as Python, Perl, and C, to create scripts that web servers can execute upon receiving user requests.

When a user interacts with a web page connected to a CGI script, the server swiftly processes the request, retrieves any required information from a database, and generates a customized HTML page that can be rendered in the user’s browser. This dynamic and real-time functionality, executed seamlessly in the background, provides users with a highly personalized experience while utilizing the wide array of web services available today.

Examples of Common Gateway Interface

Online discussion forums: In the late 90s and early 2000s, numerous online forums and message boards used Common Gateway Interface (CGI) as a way to process and store user inputs and display them as threads or posts on a website. These forums allowed users to communicate with each other, participate in discussions, and exchange knowledge.

Web-based surveys and polls: CGIs were frequently used in web-based surveys and polls that let users provide their opinions or responses to questions on a webpage. The CGI scripts processed the user inputs (form data) and displayed the results in real-time or saved them in a database for subsequent analysis and reporting.

Guestbooks: Guestbooks were a popular feature of personal websites and early blogs, allowing visitors to leave comments, messages, or just their names as a sign of their visit. Through CGI scripts, the guestbook would accept user input, store it in a file or database, and display the submitted entries on the webpage. Although guestbooks have declined in popularity with the rise of social media and advanced content management systems, they were an essential website feature during the early years of the World Wide Web.

Common Gateway Interface – FAQ

1. What is Common Gateway Interface (CGI)?

The Common Gateway Interface (CGI) is a standard protocol that allows web servers to execute external programs, called CGI scripts, and include their output in HTTP responses. This allows web servers to add dynamic content to web pages, such as forms, generated images, and other interactive features.

2. How does CGI work?

When a user requests a web page containing a CGI script, the web server processes the request, identifies the CGI script, and executes it. The script generates output, which the web server then includes in the HTTP response sent to the user. The script’s output can contain HTML, JavaScript, CSS, or other content that the browser can interpret and display.

3. What languages can be used to write CGI scripts?

CGI scripts can be written in a variety of programming languages, including Perl, Python, C, C++, Shell, Tcl, Ruby, and others. The choice of programming language depends on the developer’s preferences and the specific requirements of the project.

4. What are the advantages of using CGI?

CGI provides a simple and effective way to create dynamic web content. It allows developers to write reusable scripts that can be easily integrated into web pages and used across multiple projects. Furthermore, it supports virtually any programming language, making it adaptable to a wide range of development environments.

5. What are the disadvantages of CGI?

As a relatively old technology, CGI has some limitations compared to modern web development techniques. The execution of individual CGI scripts can consume significant server resources, leading to potential performance issues. Additionally, poorly-written CGI scripts can create security vulnerabilities, such as exposing sensitive information or allowing unauthorized access to server resources.

6. Are there alternatives to CGI for dynamic web content?

Yes, several alternatives to CGI exist for creating dynamic web content, including server-side scripting languages like PHP, ASP.NET, and Java servlets. These technologies often provide better performance and security features than CGI. Additionally, client-side JavaScript can be used to create dynamic web content without the need for server-side processing.

Related Technology Terms


  • Web server
  • Scripting language

  • HTTP requests

  • Dynamic web content
  • Server-side scripting


Sources for More Information


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