Never misconfigure your server again. Convert visually between octal numbers, symbolic notation, and raw terminal commands for Linux file permissions.
644rw-r--r--chmod 644 filenameStop guessing octal numbers. Visually map out the exact read, write, and execute permissions you need.
Toggle permissions using an intuitive 3x3 grid that maps Owner, Group, and Public classes directly to Read, Write, and Execute checkboxes.
You can interact with the checkboxes, type an octal number like `755`, or type a symbolic string like `rwxr-xr-x`, and the other two inputs will instantly sync.
Once configured, the tool outputs the exact bash command (e.g., `chmod 644 file.txt`) ready to be pasted securely into your SSH terminal.
The chmod (change mode) command is a Unix/Linux utility used by system administrators to control exactly who can read, write, or execute a file. Because Linux is a multi-user operating system, establishing strict file permissions is the foundational layer of server security.
When you run an ls -l command in a Linux terminal, you will see a strange string of characters next to your files, like -rwxr-xr--. This string is broken down into three distinct user classes, which map to the three digits in an octal number like 754.
www-data group for Apache web servers).How does a single number like '7' grant three different permissions?
Chmod uses a binary additive system. The permissions are assigned specific mathematical weights: Read = 4, Write = 2, and Execute = 1. To grant multiple permissions, you simply add the numbers together.
A Chmod Calculator performs this binary addition for all three user classes simultaneously, preventing catastrophic math errors that could expose your server.
When junior developers encounter a "Permission Denied" error while uploading files via FTP to their web server, they often find terrible advice online telling them to run chmod -R 777 /var/www.
The number 7 grants Read, Write, and Execute permissions. If you assign 777 to a file, the final '7' grants those permissions to the Public. This means any hacker on the internet can execute a malicious PHP script in that folder, or simply delete your entire website database.
Standard Web Deployments: Folders should be 755 (Owner can edit, Public can only read the folder contents). Files should be 644 (Owner can edit, Public can only view the HTML file).