I always have to look up chmod syntax. I built a free, browser-only Unix Permissions Calculator that converts between octal notation, symbolic notation, and visual checkboxes — instantly.
Live Tool
👉 https://devnestio.pages.dev/unix-permissions-calc/
What it does
- Visual checkboxes — toggle read/write/execute for owner, group, and others
-
Octal input/output — type
755and see which bits are set -
Symbolic input/output — displays
rwxr-xr-xformat -
chmod command preview — generates the exact
chmod 755 filenamecommand - Special bits — setuid, setgid, sticky bit support
- Common presets — 644, 755, 700, 777 one-click buttons
- 100% client-side — pure frontend, works offline
How Unix permissions work (quick recap)
Each permission set is 3 bits: read (4), write (2), execute (1)
rwxr-xr-x = 111 101 101 = 755
| Octal | Symbolic | Meaning |
|---|---|---|
| 7 | rwx | read + write + execute |
| 6 | rw- | read + write |
| 5 | r-x | read + execute |
| 4 | r-- | read only |
| 0 | --- | no permissions |
The tool handles all combinations including the special bits (the 4th octal digit): setuid (4000), setgid (2000), sticky (1000).
Tech stack
- Pure Vanilla JS (zero dependencies)
- Single HTML file
- CSS Grid for the permission matrix
- Hosted on Cloudflare Pages
Testing
79 tests, all passing ✅
Tests cover:
- Octal → symbolic conversion for all 512 combinations
- Symbolic → octal parsing
- Checkbox state synchronization with both inputs
- Special bits (setuid/setgid/sticky) encoding and display
- Common preset buttons producing correct values
- chmod command string generation
- Edge cases: 000, 777, 4755, 2644
- SEO and accessibility meta tags
Why browser-only?
Permission calculations are pure math — no server needed. The tool is a single HTML file, works fully offline, and your permission values stay local.
All tools at devnestio.pages.dev — free browser-only developer utilities.
Feedback welcome!
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