Difference between Java Servlet and CGI

Last Updated : 12 May, 2026

Servlet and CGI are server-side technologies used to handle client requests and generate dynamic web content. While both follow the request-response model, they differ in performance, architecture, and execution approach.

When we need high performance and scalability in web applications
When we need simple, language-independent server-side scripting

Servlet

A Servlet is a Java class used to handle client requests and generate dynamic responses on the server. It runs inside a web server using threads, making it efficient and scalable.

Thread-based approach (one thread per request)
Written in Java and runs on JVM
Supports data sharing and persistence

Real-world Example: When a user submits a login form, the servlet processes the request, validates data, and sends a response.

The diagram shows how a Servlet handles multiple requests using threads:

👁 web_server

A web server receives multiple client requests
It creates a separate thread for each request (not a new process)
Threads are lightweight and run concurrently
All threads are handled by a single servlet instance
Each request is processed independently by different threads
One servlet can serve multiple users simultaneously
Improves performance, speed, and scalability

CGI (Common Gateway Interface)

CGI is a standard protocol that allows web servers to interact with external programs to process user requests and generate responses.

Process-based approach (new process per request)
Can be written in multiple programming languages
Less efficient due to process creation overhead

Real-world Example: A web form submits data to a CGI script, which processes it and returns a result page.

Below diagram shows how CGI (Common Gateway Interface) handles multiple client requests:

👁 cgi_server

Each request creates a new process (CGI shell)
Processes run independently
Executes a CGI program for each request
Process ends after execution
Uses more memory and time
Slower and less efficient

Servlet Vs CGI

The following table explains the difference between the servlet and CGI:

Basis	Servlet	CGI
Approach	It is thread based i.e. for every new request new thread is created.	It is process-based i.e. for every new request new process is created.
Language Used	The codes are written in JAVA programming language.	The codes are written any programming language.
Object-Oriented	Since codes are written in Java, it is object oriented and the user will get the benefits of OOPs	Since codes are written in any language, all the languages are not object-oriented thread-based. So, the user will not get the benefits of OOPs
Portability	It is portable.	It is not portable.
Persistence	It remains in the memory until it is not explicitly destroyed.	It is removed from the memory after the completion of the process-basedrequest.
Server Independent	It can use any of the web-server.	It can use the web-server that supports it.
Data Sharing	Data sharing is possible.	Data sharing is not possible.
Link	It links directly to the server.	It does not link the web server directly to the server.
HTTP server	It can read and set HTTP servers.	It can neither read nor set HTTP servers.
Cost	Construction and destruction of new threads are not costly.	Construction and destruction of the new processes are costly.
Speed	Its can speed is slower.	It can speed is faster.
Platform dependency	It can be Platform Independent	It can be Platform dependent.