chmod calculator

How it works

1. Type a mode: 755, 0644, rwxr-xr-x, or -rw-r--r-- copied straight out of ls -l.
2. Read who can do what, spelled out.
3. Copy the command from the bottom of the output.
4. Special bits are named and explained when they are set.

Frequently asked questions

Why does 4755 have four digits?

The first digit carries the special bits: 4 is setuid, 2 is setgid, 1 is sticky. They are added together like the others, so 6755 has both setuid and setgid.

What is the sticky bit for?

On a directory, it means only the owner of a file may delete it, whatever the directory’s own permissions say. /tmp is the reason it exists: everyone can write there, and nobody can remove anybody else’s files.

Why is the s sometimes a capital S?

Because the bit is set but the execute bit under it is not — setuid on something that cannot be executed. ls shows it in capitals to say “this is set, and it is doing nothing”, which is almost always a mistake.

What should I actually use?

644 for files and 755 for directories covers most of it. 777 is almost never the answer, and if something only works at 777 the problem is ownership, not permissions.

Is anything sent to a server?

No. It runs in your browser, so what you paste stays on your computer.