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Chmod Calculator

Runs on your device. Nothing is sent.

Permissions

WhoReadWriteExecuteDigit
Owner7
Group5
Others5
Special bits
Paste what ls -l shows, like -rw-r--r-- or drwxr-xr-x.
Common permissions
755: folders, scripts and programs: the owner edits, everyone reads and runs

Result

755-rwxr-xr-x
chmod with numberschmod 755 file.txt
chmod with letterschmod u=rwx,g=rx,o=rx file.txt
Owner:
read, change, run it as a program
Group:
read, run it as a program
Others:
read, run it as a program

Apply a chmod change

Type what you'd pass to chmod to see what it does to ⁦755⁩ - the same rules as GNU chmod.

Who: u owner, g group, o others, a all. Then + adds, - removes, = sets: r, w, x, X, s, t. Separate with commas.
755 → 755rwxr-xr-xNothing changes.

Umask

The umask takes permissions away from new files and folders. Type one to see what new files get.

New files
644 -rw-r--r--
New folders
755 drwxr-xr-x
As letters
umask -S → u=rwx,g=rx,o=rx

Work out Linux file permissions: tick boxes or type 755 or rwxr-xr-x, get the chmod command, apply u+x style changes and see what a umask gives.

Linux and macOS give every file and folder three sets of permissions - for its owner, its group and everyone else - written as numbers like 755 or letters like rwxr-xr-x. Tick the boxes or type either form and get both, plus the chmod command ready to copy and a plain-language explanation of who can do what. You can also try a chmod change like u+x,go-w (worked out exactly as GNU chmod does) and see what files get under a umask.

Frequently asked questions

What does chmod 755 mean?
Each digit is one group of people - owner, group, others - and is the sum of read (4), write (2) and execute (1). 7 = 4 + 2 + 1, so the owner can read, write and run; 5 = 4 + 1, so the group and everyone else can read and run but not change. In letters that's rwxr-xr-x.
Should I use 644 or 755?
644 for ordinary files (web pages, images, documents), 755 for folders and for scripts or programs that need to run. Folders need execute (x) to be opened at all, which is why they get 755.
Why is chmod 777 a bad idea?
777 lets every user and every process on the machine change or delete the file, and on a web server that includes a hacked plugin. Fix the owner with chown, or use 775/664 with a shared group, instead.
What are setuid, setgid and the sticky bit?
They're the optional first digit. Setuid (4) runs a program with its owner's rights, like passwd. Setgid (2) on a folder makes new files inside inherit its group, handy for shared project folders. Sticky (1) on a folder like /tmp lets everyone write but only owners delete. ls -l shows them as s and t in place of x.
What is a umask?
The bits taken away from new files and folders. Programs ask for 666 for files and 777 for folders, and the umask removes from that: the common 022 gives 644 and 755, while 077 gives 600 and 700 so new files are private.
Is anything sent to a server?
No. All calculations run in your browser, so the page also works offline. A copied link only contains the mode, like ?mode=755.

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