Chmod Calculator
| Role | Read (r) | Write (w) | Execute (x) |
|---|---|---|---|
| Owner | |||
| Group | |||
| Others |
How to Use
Toggle the permission checkboxes for owner, group, and others. The numeric (octal) and symbolic representations update instantly. You can also enter a 3-digit octal number directly.
What are Unix File Permissions?
Unix file permissions are a security mechanism that controls who can read, write, or execute a file or directory. Every file on a Unix-like system (Linux, macOS) has three permission groups: the owner (user who created the file), the group (users sharing a group identity), and others (everyone else). Each group can be granted read, write, and execute permissions independently. Permissions are represented in two formats: symbolic notation (rwxr-xr-x) which shows each permission as a letter, and octal notation (755) which uses a three-digit number. The chmod command is used to change these permissions from the command line.
Octal Notation
Unix file permissions control read (4), write (2), and execute (1) access for three groups: owner, group, and others. The octal representation is the sum of these values for each group. For example, 755 means rwx for owner, r-x for group and others.
Common Use Cases
- Server administration — set correct permissions for web server files and directories
- Deployment scripts — configure chmod commands in CI/CD pipelines to secure application files
- Security auditing — verify that sensitive files like configuration and key files are not world-readable
- Shared hosting — manage permissions when multiple users access the same server
- Shell scripts — make scripts executable with the right permission level
Common Permission Values
755 (rwxr-xr-x) — standard for executable files and directories. 644 (rw-r--r--) — standard for regular files. 700 (rwx------) — private, owner-only access. 600 (rw-------) — private files like SSH keys. 777 (rwxrwxrwx) — full access for everyone, generally insecure and should be avoided.
Privacy
All processing happens in your browser. No data is sent to any server.
FAQ
What is the difference between octal (755) and symbolic (rwxr-xr-x) notation?
They are two ways of writing the same permissions. Octal sums read (4), write (2), and execute (1) into a three-digit number, while symbolic notation spells out each permission as r, w, or x. This tool shows both at once.
Is the permission configuration I enter sent to a server?
No. All calculations happen entirely in your browser, and the values you enter and commands generated are never sent to or stored on any server.
Does it support special permissions like setuid or the sticky bit?
This tool handles the basic three digits — read, write, and execute for owner, group, and others. It does not support the fourth digit used for setuid, setgid, or the sticky bit.
Is it safe to set permissions to 777?
777 (rwxrwxrwx) grants read, write, and execute to everyone and is generally discouraged for security reasons. It's typically safer to use 644 for files and 755 for directories and executables.
Can I type an octal number directly to inspect permissions?
Yes. Enter a three-digit octal value like 755 and the matching checkboxes, symbolic notation, and chmod command update automatically.