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chmod Calculator

Calculate and convert Unix file permission modes between octal and symbolic.

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Runs 100% in your browser - your data never leaves your device

Owner: read, write, execute; Group: read, execute; Other: read, execute
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How to Use the chmod Calculator

  1. Enter an octal code (such as 755 or 4755) in the Octal Permission Code field. The symbolic string updates instantly.
  2. Or enter a symbolic string (such as rwxr-xr-x) in the Symbolic Permission String field. The octal code updates instantly.
  3. Read the description below the fields to see a plain-English summary of the permission (Owner, Group, Other).

What This Tool Does

The chmod Calculator converts Unix file permission modes bidirectionally between octal notation (e.g. 755) and symbolic notation (e.g. rwxr-xr-x). It handles all nine rwx bits for owner, group, and other, as well as the three special bits: setuid (4000), setgid (2000), and sticky (1000). Conversion is pure client-side JavaScript with no server calls.

Common Permission Modes

  • 644 (rw-r--r--) - the default for regular files: owner edits, everyone else reads. Right for web assets, configs, and source files.
  • 755 (rwxr-xr-x) - the default for directories and executables: owner has full control, everyone can enter the directory or run the program.
  • 600 (rw-------) - private files such as SSH private keys and .env files. OpenSSH refuses keys that are more permissive than this.
  • 700 (rwx------) - private directories like ~/.ssh itself.
  • 664 / 775 - group-writable variants used on shared deploy directories where a team group needs write access.

Gotchas Worth Knowing

Octal modes are position-sensitive: 4755 and 755 differ by the setuid bit, which makes an executable run as its owner - a security-relevant change you should make deliberately, never by copy-paste. A capital S or T in symbolic output means the special bit is set but the matching execute bit is not, which is usually a mistake. Directories need the execute bit to be entered at all; a directory at 644 is readable in listings but cannot be opened. And chmod -R 777 is almost never the fix - it silences permission errors by making every file world-writable, which most web servers and SSH explicitly flag as insecure.

Frequently Asked Questions

What does chmod 755 mean?

chmod 755 sets owner read, write, and execute; group read and execute; other read and execute. In symbolic form this is rwxr-xr-x. It is common for directories and executables that should be world-readable but only owner-writable.

What are the setuid, setgid, and sticky bits?

These are the three high bits (4000, 2000, 1000). Setuid (4000) on an executable runs it as the file owner; setgid (2000) runs it as the group owner; sticky (1000) on a directory prevents users from deleting files they do not own, as used on /tmp. In symbolic notation, setuid replaces the owner execute slot with s (or S when execute is not set), setgid replaces the group execute slot, and sticky replaces the other execute slot with t or T.

Is anything sent to a server?

No. All conversion runs entirely in your browser with no network requests. Your permission strings never leave the tab.

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