About this tool
What does it calculate?
Unix file permissions: the rwxrwxrwx triple maps to octal (755, 644) and symbolic (u+x) forms. This tool translates both ways and explains what each bit allows — the end of permission guesswork.
How to use it
- Toggle read/write/execute per owner, group and other.
- Copy the octal number or symbolic string.
- Apply with chmod on the target system.
Examples
- Scripts need 755 (executable); configs usually 644; secrets 600.
- Fixing “Permission denied” on a deploy key: 600, owned by the user.
- Making a directory listable yet files private: 755 dirs, 644 files.
Important limitations
- chmod sets discretionary permissions only — ACLs, SELinux and mounts can override.
- 777 is almost never the answer; it grants the world write access.
- Ownership (chown) is separate from mode — both must be right.
Privacy
Local bit math. Nothing uploaded.
Frequently asked questions
755 vs 644?
755 adds execute (needed for scripts/directories); 644 is files that only get read.
What does the first digit (2755) mean?
Special bits: setuid/setgid/sticky — advanced, use deliberately.
Recursive chmod safe?
Dangerous with wrong modes — files and directories usually need different bits.