logohsb.horse

chmod Simulator

Apply a numeric or GNU symbolic mode to a current mode and inspect the resulting permission bits in your browser.

Preview ordered comma clauses, continued operations, conditional X, permission copying, special bits, and umask without touching a file.

Modes are calculated only in this browser.

Current mode

For example: 755, 0755, 4755, rwxr-xr-x, or rwsr-xr-x

Target
Mode to apply

For example: 644, u+x, g-w,o-r, a=rw, o+g, or og+rX-w

umask

Used only by symbolic modes where the user classes are omitted.

Result

Enter the current mode and a mode to apply.

How to use

  1. 1

    Enter the current state

    Provide the current mode and choose a regular file or directory.

  2. 2

    Enter a chmod mode

    Enter a numeric or symbolic mode. Check umask when user classes are omitted.

  3. 3

    Inspect changed bits

    Review octal and symbolic forms, each class, special bits, and the change made by each operation.

Simulation scope

This simulates GNU Coreutils mode-bit calculations. It excludes ACLs, ownership, effective users, symlinks, recursion, and OS policies that clear setid bits. For directories, numeric modes of four or fewer digits preserve existing setuid and setgid bits as GNU chmod does.

FAQ

How does X differ from x?
x always affects execute/search. X applies only to a directory or to a file where at least one execute bit is already set.
Are +w and a+w the same when users are omitted?
No. +w leaves bits protected by umask untouched, while a+w explicitly ignores umask.
Does this change a real file?
No. It calculates only the mode bits entered in this browser.