Chmod Permission Calculator
Check the read/write/execute boxes for the owner, group, and other, and this tool shows the octal notation (e.g. 755), the symbolic notation (e.g. rwxr-xr-x), and a ready-to-use chmod command in real time. You can also type an octal or symbolic value directly and the other fields update to match, including special permissions like setuid, setgid, and the sticky bit. Everything happens in your browser, and nothing you type is ever sent to a server. If you work with file paths using regular expressions, try the Regex Tester as well.
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| Subject | Read (r) | Write (w) | Execute (x) |
|---|---|---|---|
| Owner (u) | |||
| Group (g) | |||
| Other (o) |
Notes
- Octal notation can be entered as 3 digits (e.g. 755) or 4 digits (e.g. 4755). With 3 digits, setuid/setgid/sticky are all off; with 4 digits, the leading digit sets these special permissions.
- Symbolic notation accepts the 9-character "rwxr-xr-x" form, or the raw "ls -l" output "-rwxr-xr-x" (10 characters, with a leading file-type character).
- When setuid or setgid is set without the matching execute permission, the symbolic notation shows an uppercase S in that position (and uppercase T for the sticky bit) — this is the standard convention.
Glossary
Permissions (file access mode)
On Linux/Unix and macOS filesystems, permissions control who can read (r), write (w), and execute (x) a file. They can be set independently for the owner, the group, and everyone else (other).
Octal notation (e.g. 755)
Read = 4, write = 2, execute = 1 — add these up for the owner, group, and other, and you get three digits (0-7 each), as used in commands like "chmod 755".
Symbolic notation (e.g. rwxr-xr-x)
A 9-character format spelling out r (read), w (write), and x (execute), with "-" where a permission is missing — the same format shown by the "ls -l" command.
setuid, setgid, and the sticky bit (special permissions)
These special bits sit alongside the usual r/w/x. setuid makes a program run with the file owner's privileges, and setgid makes it run with the group's privileges (on a directory, it also makes new files inherit that group). The sticky bit, set on a directory, prevents anyone but the owner from deleting files inside it. In octal this is a 4th leading digit (e.g. 4755); in symbolic notation it shows up as s/S or t in the execute position.
FAQ
What is the difference between chmod 755 and 644?
755 gives the owner read, write and execute, while group and others get read and execute. It suits executables and directories. 644 gives the owner read and write and everyone else read only, which suits regular files.
What are setuid and the sticky bit?
Setuid makes a program run with the file owner's privileges, and setgid with the group's. The sticky bit on a directory prevents users other than the owner from deleting files in it. In octal they appear as a leading fourth digit, for example 4755.
Is it safe to set permissions to 777?
777 lets anyone read, write and execute, which is a security risk. Follow the principle of least privilege and start from settings like 755 or 644.
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