Key Features
Owner / group / others × read / write / execute checkbox grid with live octal value
Numeric-to-symbolic file mode output (e.g. 755 → rwxr-xr-x) with directory bit
Special bits: setuid (4000), setgid (2000), and sticky (1000) with s/S/t/T letters
Reverse decoding: type any 3–4 digit octal mode to load its permissions
Nine common presets from safe (600) to sticky /tmp (1777), each with a note
Copy buttons for both numeric and symbolic chmod commands
How to Use
1Toggle the read/write/execute boxes for owner, group, and others
2Read the octal code and symbolic mode, switching File/Directory as needed
3Optionally set special bits (setuid, setgid, sticky)
4Copy the numeric or symbolic chmod command into your terminal
Common Use Cases
Fix "permission denied" errors by picking the right mode instead of guessing
Harden a server: verify SSH keys are 600 and ~/.ssh is 700
Understand an unfamiliar mode you found in docs or a Dockerfile
Learn what setuid, setgid, and the sticky bit actually do
Frequently Asked Questions
What does chmod 755 mean?
The owner may read, write, and execute (7); group and others may read and execute (5 each). It is the standard mode for directories and executable programs.
Why is 777 dangerous?
It lets every user on the system read, modify, and execute the file — or create and delete files inside the directory. Prefer 755 (dirs/programs) or 644 (regular files), and 600 for secrets.
What is the sticky bit (1777)?
The sticky bit restricts deletion: even when everyone can write to a directory, only the file's owner can delete it. /tmp uses 1777 for exactly this reason.
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