Unix Permissions Calculator – Visual chmod Tool with Octal & Symbolic Notation

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Unix Permissions Calculator

A visual browser tool for calculating Unix file permissions: devnestio.pages.dev/unix-permissions-calc/

Features

Visual checkboxes for Owner / Group / Other × Read / Write / Execute
Real-time conversion between octal (e.g. 755) and symbolic (rwxr-xr-x)
Direct input — type an octal or symbolic value and checkboxes update instantly
12 common presets — 644, 755, 700, 600, 777, sticky dir, setUID, and more
Per-entity breakdown — see Owner/Group/Other values and descriptions separately
Copy buttons for octal and symbolic forms
Zero dependencies, instant load

Permission Bits Cheat Sheet

Octal	Binary	rwx	Meaning
7	111	rwx	Read, write, execute
6	110	rw-	Read and write
5	101	r-x	Read and execute
4	100	r--	Read only
3	011	-wx	Write and execute
2	010	-w-	Write only
1	001	--x	Execute only
0	000	---	No permissions

Common Presets

644  rw-r--r--   Public web file (owner rw, group/other r)
600  rw-------   Private file (owner rw only)
755  rwxr-xr-x   Executable / public directory
700  rwx------   Private directory
777  rwxrwxrwx   Full access (use with caution)
444  r--r--r--   Read-only for all

The Math

Each octal digit maps to 3 bits (r=4, w=2, x=1):

function bitsToOctal(b) {
  const owner = (b[0]<<2)|(b[1]<<1)|b[2]; // e.g. 7
  const group = (b[3]<<2)|(b[4]<<1)|b[5]; // e.g. 5
  const other = (b[6]<<2)|(b[7]<<1)|b[8]; // e.g. 5
  return '' + owner + group + other; // '755'
}