What does chmod 755 mean?

755 is the numeric representation of file permissions in Unix/Linux. 7 means owner has rwx, 5 means group has rx, 5 means others have rx. This is standard for web server files.

How to convert between symbolic and numeric modes?

Symbolic mode like u=rwx,g=rx,o=r converts to numeric 754. Calculation: r=4, w=2, x=1. Owner: 4+2+1=7, Group: 4+0+1=5, Others: 4+0+0=4.

What are common file permissions?

Common permissions: 644 (default file, rw-r--r--), 755 (default dir/script, rwxr-xr-x), 700 (private, rwx------), 777 (open, rwxrwxrwx, not recommended), 600 (private file, rw-------).

Does chmod support special permissions?

Yes, chmod supports SUID (4xxx), SGID (2xxx) and Sticky Bit (1xxx). For example, chmod 4755 sets the SUID bit, making the program run with owner's privileges.

🔐 Chmod Calculator

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Updated: 2026-07-11