chmod Calculator: Toggle bits, read the chmod command instantly.

chmod 755 sets read, write and execute for the owner (7 = 4+2+1) and read plus execute — but not write — for the group and everyone else (5 = 4+0+1). Symbolically it is rwxr-xr-x. It is the usual mode for directories and executables: the owner can change the contents while everyone else can only read and run them.

They describe the same nine permission bits two ways. Octal packs each read/write/execute triad into one digit 0–7 (rwx = 7, r-x = 5, rw- = 6), so 644 means rw-r--r--. Symbolic spells the bits out as three groups of rwx for owner, group and other. This calculator keeps both — plus the checkbox matrix — in sync, so editing any one updates the rest instantly.

The optional leading digit carries the special bits: 4 = setuid, 2 = setgid, 1 = sticky (they add, so 6 = setuid+setgid). You only need the fourth digit when one of those is set — 4755 is setuid + rwxr-xr-x. When the special digit is zero the conventional form drops it, so 0755 is written simply as 755.

setuid (4000) makes an executable run as its owner rather than the caller; setgid (2000) runs it as its group, or on a directory makes new files inherit that directory’s group. The sticky bit (1000) on a shared directory like /tmp lets users delete only their own files. In symbolic mode they appear in the execute slots as s/S (setuid/setgid) and t/T (sticky) — uppercase when the underlying execute bit is off.

A lowercase s in the owner or group execute slot means that special bit is set and execute is also on (setuid or setgid). An uppercase S means the special bit is set but execute is off — often a mistake. Likewise t in the other-execute slot is the sticky bit with execute on, and T is sticky with execute off. This tool renders all of them exactly as ls -l would.

The first character is the file type (- for a regular file, d for a directory, l for a symlink); the next nine are the owner, group and other rwx triads. Paste a full 10-character string like -rwxr-xr-x into the symbolic field and the calculator strips the type character and shows the octal and chmod command.

No. The conversion is pure bit math running 100% in your browser — there is no server, no account and no logging. The permission values you enter never leave your device.

Yes. Every valid value updates the URL with an #m= fragment (for example #m=755), and the Copy link button copies that full URL. Open it later or send it to a teammate and the calculator restores that exact mode.

chmod 777 gives read, write and execute to the owner, the group and every other user (rwxrwxrwx), so any account on the system can modify, replace or delete the contents. chmod 755 (rwxr-xr-x) keeps write access with the owner alone and lets everyone else only read and execute. 777 is almost never the right fix for a permission error; 755 for directories and scripts and 644 for ordinary files cover most cases.

Give each permission a value — read 4, write 2, execute 1 — and add them up separately for the owner, the group and others, which yields three digits. For example, rw- is 4 + 2 = 6 and r-- is 4, so rw-r----- is 640. A fourth leading digit adds setuid (4), setgid (2) and the sticky bit (1). Tick the boxes in the calculator and it does the addition, showing the octal value, the symbolic string and the chmod command together.

chmod -R applies one mode to a directory and everything beneath it, files and subdirectories alike. That is the problem with -R 777 (or even -R 755): every regular file becomes executable, and with 777 writable by every user on the machine. Set directories and files separately instead, with find . -type d -exec chmod 755 {} + and find . -type f -exec chmod 644 {} +, or use chmod -R u=rwX,go=rX, where the capital X adds execute only to directories and files that are already executable.

chmod +x adds execute permission for the owner, the group and others, but because it names no who-letter, any bit set in your umask is left alone: under umask 077 only the owner gains it, while chmod a+x sets all three regardless. Execute is what lets you run a script directly, so ./deploy.sh fails with Permission denied until it is set, and the script should still begin with a shebang line such as #!/bin/sh so it runs under the intended interpreter. Use chmod u+x to make a file executable for the owner alone. On a directory, x means traverse: permission to enter it and reach the files inside.