What chmod 644 does: owner reads and writes, everyone else only reads
Runs in your browser. Nothing you type is sent anywhere. Updated on 24 Oct 2026.Chmod 644 is the normal mode for a plain file such as an HTML page, a config file or a document. The owner digit 6 is read plus write, and the 4s let the group and everyone else read it but not change or run it. In ls -l it reads rw-r--r--. It is also what a umask of 022 gives every new file by default.
Open the page with 644 already set: rw-r--r--.
Read the breakdown: the owner can read and write; group and others can only read.
Turn on u=rwx form for the symbolic version of the command.
Type the file name in File or directory and press Copy.
This chmod calculator converts Unix and Linux file permissions between the octal number, such as 755, and the symbolic letters that ls -l prints, such as rwxr-xr-x. Tick the read, write and execute boxes for the owner, the group and everyone else, type a number, or paste the permission column from ls -l, including the leading file type letter; all three stay in step.
Each digit is a sum: read is 4, write is 2 and execute is 1. The owner's 7 is 4 + 2 + 1, the group's 5 is 4 + 1. A fourth digit in front holds the special bits: setuid (4) runs a program as its owner, setgid (2) runs it as its group or makes a directory's new files inherit the group, and sticky (1) lets people delete only their own files in a shared directory like /tmp. In the letters these show as s or t in the execute position, and as a capital S or T when execute is not also set, which usually means a mistake.
The umask box shows what a umask does to new files, which start from 666, and new directories, which start from 777. A umask of 022 gives 644 and 755; 077 gives 600 and 700.
The rest of the article, and all 6 questions about Chmod Calculator, are on the Chmod Calculator page.
The owner gets 7, which is read (4) plus write (2) plus execute (1). The group and everyone else get 5, read plus execute. So anyone can run the program or open the directory, but only the owner can change it. In ls -l it appears as rwxr-xr-x.
Both let only the owner write. 755 adds execute for everyone, which a script, a program or a directory needs; 644 leaves execute off, which suits ordinary files such as web pages, images and configuration. Giving a plain file 755 is harmless but unnecessary.
Mode 777 lets every user on the machine change, replace or delete the file, and run it. On a web server that means any compromised process can rewrite your code. Directories that really must be shared should use 1777, which adds the sticky bit so people can delete only their own files.
Programs normally create files with 666 and directories with 777, and every bit set in the umask is removed. With umask 022, files come out as 644 and directories as 755. With 077 they are 600 and 700, private to the owner. A umask never adds permissions.
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