Chmod Calculator

Three sevens mean “read + write + execute” for owner, group, and everyone. It is the most permissive chmod value and is almost never appropriate in production – it lets any local user modify or replace the file.

Regular HTML/PHP/text files usually sit at 644 (owner read+write, everyone else read-only). Directories usually sit at 755 (owner full, everyone else read+traverse). Private config files live at 600 or 640.

Ten characters: one for file type (-, d, l, b, c, p, s), then three triplets of r/w/x for owner, group, and other. A dash means permission denied; a letter means granted.

Special bits that modify how a file executes or how a directory behaves. Setuid runs the program as its owner (used by tools like sudo as 4755). Setgid makes new files inherit the directory’s group. The sticky bit, most famous on /tmp (1777), lets users only delete their own files.

755 gives the owner full access and everyone else read + execute. 775 also gives the group full access – useful when multiple developers on the same group need write access without opening the file up to the wider world.

When no special bits are set, the octal is three digits (644). When any of setuid, setgid, or sticky is on, the octal gains a leading digit (4755, 2770, 1777). The tool drops the leading zero automatically when none of the special bits apply.

Setuid or setgid without the matching execute bit shows as uppercase S – the special bit is set but not effective. Sticky without execute on other shows as uppercase T. Useful for spotting misconfigured permissions.

Yes. Paste a 3- or 4-digit octal (each digit 0-7) into the octal box. Invalid characters are stripped automatically; the error block appears only when the result is still not a valid permission value.

No. Every computation is a few bitwise operations in your browser. There are no fetch, XHR, or analytics calls on your permissions or filenames.

After the page loads, yes. HTML, CSS, and JS are self-contained – disconnect Wi-Fi and keep calculating.