~/devtools / chmod
tool::chmod

chmod
Calculator

Bidirectional Unix/Linux file permission calculator. Toggle rwx checkboxes or type a numeric value like 755 and see both representations instantly.

ad · 728×90

Presets

rwxOctalSymbolic
Owner7rwx
Group5r-x
Others5r-x
rwxr-xr-x
$chmod 755 filename
ad · 300×250
// about this tool

About chmod Calculator

In Unix/Linux, chmod (change mode) is the command used to change the access permissions of files and directories. Permissions are divided into three categories: Owner (User), Group, and Others — each with three bits: read (r=4), write (w=2), and execute (x=1).

Numeric notation (e.g. 755) represents the sum of the bits for each category. 7 means rwx (4+2+1), 5 means r-x (4+0+1), and 4 means r-- (4+0+0). Symbolic notation (e.g. rwxr-xr-x) is what you see in the output of ls -l and is more human-readable.

This tool provides bidirectional conversion between checkboxes and numeric input, six common presets (755, 644, 600, 777, 700, 444), and a real-time chmod command preview so you can copy and paste it directly into your terminal.

Key Use Cases
  • ▸Setting correct permissions for web server files (644) and directories (755)
  • ▸Verifying SSH private key security with restricted permissions (600)
  • ▸Granting execute permission to shell scripts and build artifacts (755)
  • ▸Checking permissions in CI/CD deployment scripts and workflows
  • ▸Debugging file permission issues inside Docker containers
FAQ
Q. Why is chmod 777 dangerous?
777 grants read, write, and execute permissions to everyone — owner, group, and all other users. Anyone can modify or execute the file, creating serious security vulnerabilities. Never use it in a web server environment.
Q. What permissions do SSH keys require?
SSH private keys (~/.ssh/id_rsa) must have 600 permissions (owner read/write only). If the permissions are too broad, SSH will refuse to use the key and you'll see a 'Permissions too open' error.
Q. Are directory permissions different from file permissions?
Yes. For directories, the execute (x) bit means the ability to enter (cd into) the directory, not to run it as a program. Read (r) allows listing contents, write (w) allows creating or deleting files inside.