Chmod Master
Convert Linux permissions between octal, symbolic notation and a visual grid.
Permissions grid
| Read | Write | Execute | |
|---|---|---|---|
| Owner | |||
| Group | |||
| Others |
Values
What is chmod?
chmod is the Linux/Unix command used to control who can read, write or execute a file or folder — separately for the file's owner, its group, and everyone else. Permissions can be written as an octal number (like 755) or as symbolic text (like rwxr-xr-x), and both mean the same thing but aren't easy to convert between by hand. This tool lets you set permissions visually with checkboxes and instantly see the matching octal, symbolic notation and ready-to-run chmod command.
How to use Chmod Master
- Check the boxes in the Permissions grid for Read/Write/Execute per Owner, Group and Others — or click a preset like 755 or 644.
- Read the resulting Octal and Symbolic values, which update automatically.
- Optionally type a filename in Target to fill in the ready-to-run command.
- Click the copy icon next to the octal or symbolic command to copy it for your terminal.
How Linux permissions work
Every file or directory carries three permission sets — owner, group and others — each with read, write and execute. In octal notation, each set is a single digit that sums read (4), write (2) and execute (1):
754 → owner 7 = 4+2+1 = rwx → group 5 = 4+0+1 = r-x → others 4 = 4+0+0 = r-- → symbolic: rwxr-xr--
An optional 4th digit in front (e.g. 4755) sets the special bits: setuid (4), setgid (2) and the sticky bit (1), following the POSIX IEEE Std 1003.1 permission model. This tool computes all three representations — octal, symbolic and the checkbox grid — from each other entirely in your browser, plus the exact chmod command to copy and run.
Frequently asked questions
How do I read an octal permission like 755?
Each digit is the sum of read (4), write (2) and execute (1) for owner, group and others in that order. 755 means owner=rwx (4+2+1=7), group=r-x (4+0+1=5), others=r-x (4+0+1=5).
What do setuid, setgid and the sticky bit do?
They're an optional 4th octal digit. Setuid (4) makes a program run with its owner's privileges. Setgid (2) makes new files in a directory inherit the directory's group. The sticky bit (1) on a directory means only a file's owner can delete or rename it, even if others have write access — this is how /tmp is usually configured.
Why does the symbolic notation show an uppercase S or T sometimes?
A lowercase s or t means the special bit is set AND the matching execute bit is also set. An uppercase S or T means the special bit is set but execute is off for that category — which is usually a configuration mistake, since setuid/setgid have no effect without execute permission.
Does this tool actually change permissions on my files?
No. It only computes the octal value, symbolic string and the exact chmod command — nothing runs on a server or touches your filesystem. Copy the generated command and run it yourself.