Chmod Calculator

How the Chmod Calculator works

Unix and Linux give each file three sets of permissions: for its owner, its group and everyone else. Each set can allow read, write and execute. Tick the boxes, or type the permissions as a number (755) or as letters (rwxr-xr-x, or with the leading character that ls -l shows), and the other forms and the chmod command update.

The optional fourth digit, written first, adds setuid (4), setgid (2) and the sticky bit (1). They show as s and t in place of x, or as capital S and T when execute is off.

Examples

Common settings

755 = rwxr-xr-x (programs and folders); 644 = rw-r--r-- (ordinary files); 640 = owner can read and write, the group can read, others have no access.

Special bits

1777 = rwxrwxrwt, the /tmp folder: anyone can create files, but only a file's owner can delete it. 4755 = rwsr-xr-x, a setuid program.

Frequently asked questions

Should I use chmod 777?

Almost never. It lets every user on the system change or replace the file. For websites, 644 for files and 755 for folders is the usual safe choice.

What does execute mean for a folder?

Permission to enter it and reach the files inside. A folder with read but no execute lists names but won't open them.

How do I apply it to every file in a folder?

chmod -R 755 folder changes everything inside. To give files and folders different permissions, use find with -type f and -type d.

Related tools

Command

How the Chmod Calculator works

Formula