What Is Change Mode (chmod)?

What is Change Mode (chmod)?

What is Change Mode (chmod)? A Web Developer’s Guide

Have you ever come across the term “chmod” while working with a web server or in the context of file permissions? If you’re new to web development or system administration, this term might be unfamiliar to you. But fear not! In this blog post, we will delve into the world of “chmod” and help you understand its significance and how it relates to your work.

Understanding Change Mode (chmod)

In the context of file systems and Unix-like operating systems, Change Mode, commonly abbreviated as “chmod,” is a command that allows users to modify the permissions of a file or directory. These permissions determine who can read, write, or execute the file or directory. By using the chmod command, you can control the access rights of various user groups, providing an added layer of security to your web server or applications.

Key Takeaways:

  • Control over file permissions: Chmod gives you control over the permissions of files and directories on a web server or any Unix-like operating system.
  • Improved security: By setting appropriate permissions, you can restrict access to sensitive files and directories, preventing unauthorized modifications or access.

How does chmod work?

Chmod operates using a numeric or symbolic representation to assign permissions to files and directories. The permissions can be categorized into three groups: owner, group, and others. Each group can be granted read (r), write (w), and execute (x) permissions. Here’s a breakdown of the different values:

  • Read (r): Allows a user to view the content of a file.
  • Write (w): Enables a user to modify or delete the content of a file.
  • Execute (x): Grants permission to execute a file if it is a script or program.

In addition to the above values, chmod supports various permission modes:

  • Numeric representation: Each permission is assigned a value: read (4), write (2), and execute (1). These values are then summed up to form a three-digit number representing the permission mode. For example, 777 grants full permissions to the owner, group, and others.
  • Symbolic representation: Uses a combination of letters and symbols to represent the permission mode. The symbolic representation allows you to modify permissions selectively for each group. For example, “u+r” grants read permission to the owner, while “go-w” removes write permission for the group and others.


Change Mode (chmod) is a powerful command that gives you control over file permissions on your web server or any Unix-like operating system. By utilizing chmod effectively, you can ensure that your files and directories are secure and accessible to the appropriate users. Whether you are a web developer or a system administrator, understanding chmod is essential for maintaining the integrity and security of your web applications.

So, the next time you encounter “chmod,” don’t panic! Embrace it as a versatile tool in your developer arsenal and harness its power to fortify your web server’s security.