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Chmod Calculator

Convert between checkboxes, octal numbers like 755 and symbolic permissions like rwxr-xr-x.

Runs locally — files never leave your device

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How to use Chmod Calculator

  1. 1Tick read, write and execute for the owner, the group and others — or type a mode such as 644 or rwxr-xr-x.
  2. 2Optionally set the special bits setuid, setgid or sticky.
  3. 3Read the octal value, the symbolic notation and a plain description of who can do what.
  4. 4Enter a file name and copy the ready-made chmod command.

Understand and set Linux file permissions

Every file and directory on Linux, macOS and other Unix-like systems has permissions that control who can read it, change it and run it. They're written either as a number like 755 or as letters like rwxr-xr-x, and set with the chmod command. This calculator converts between the two forms, explains what each setting allows and gives you the exact command to run.

Features

  • Checkbox grid for read, write and execute for owner, group and others.
  • Type a mode in octal (644, 4755) or symbolic form (rw-r--r--).
  • Special bits: setuid, setgid and sticky.
  • Plain-language summary of the permissions.
  • Ready-to-copy chmod command for your file name.
  • Common presets with what they're used for.

How the numbers work

Each digit is the sum of read (4), write (2) and execute (1):

Digit Permissions Symbolic
7 read + write + execute rwx
6 read + write rw-
5 read + execute r-x
4 read only r--
0 no access ---

The three digits apply to the owner, the group and everyone else, in that order. A fourth leading digit sets the special bits.

Typical permissions

Mode Use
644 Regular files, web pages, images
755 Scripts, programs and directories
600 Private files such as SSH keys and .env files
700 Private directories such as ~/.ssh
664 / 775 Files and folders shared with a group
400 Read-only secrets, e.g. cloud key files

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Frequently asked questions

What does chmod 755 mean?
7 for the owner (read 4 + write 2 + execute 1), 5 for the group (read 4 + execute 1) and 5 for others. The owner can read, change and run the file; everyone else can read and run it but not change it. It's the usual setting for scripts, programs and directories.
What does chmod 644 mean?
The owner can read and write; the group and others can only read. It's the standard permission for ordinary files such as web pages, images and configuration files.
Why is chmod 777 a bad idea?
777 lets every user on the system read, modify and run the file. On a web server this can let other accounts or a compromised process change your files. Use the most restrictive permissions that still work — usually 644 for files and 755 for directories.
What does execute mean for a directory?
For directories, "execute" means permission to enter the directory and access files inside it, and "read" means permission to list its contents. A directory usually needs both, so 755 or 700 rather than 644.
What are setuid, setgid and the sticky bit?
Setuid (4000) runs a program with the file owner's permissions, setgid (2000) runs it with the group's permissions or makes new files in a directory inherit its group, and the sticky bit (1000) on a shared directory such as /tmp lets users delete only their own files. They appear as s, s and t in symbolic notation.

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