What does chmod 755 mean?
Understand chmod octal permissions like 755 and 644, and build them with a visual calculator.
chmod 755 sets file permissions to rwxr-xr-x: the owner can read, write, and execute; the group and everyone else can read and execute but not write. Each digit is a sum of read (4), write (2), and execute (1), so 7 = rwx and 5 = r-x.
Input
755
Output
rwxr-xr-x (owner: rwx · group: r-x · others: r-x)
7 = 4+2+1 (rwx), 5 = 4+0+1 (r-x). 644 = rw-r--r-- is the common default for files.
Open the chmod Calculator → Free · runs in your browser · nothing uploaded
Steps
- Open the chmod tool and enter an octal value (e.g. 755) or toggle the permission checkboxes.
- Read the symbolic form (rwxr-xr-x) and the meaning for owner, group, and others.
- Use 755 for directories and executables, 644 for ordinary files.
- Avoid 777 (world-writable) — it is almost never the right choice.
Frequently asked questions
- What is the difference between 755 and 644?
- 755 (rwxr-xr-x) grants execute to everyone and write to the owner — used for directories and scripts. 644 (rw-r--r--) has no execute bit and is the normal setting for regular files like documents and config.
- Why is 777 dangerous?
- 777 (rwxrwxrwx) lets any user read, modify, and execute the file. On shared or web-facing systems that is a serious security risk; grant the least access that works instead.