chmod 644 Permission Explained: Standard for Files

Octal

644

Symbolic

rw-r--r--

Binary

110 100 100

Risk Level

Low Risk

Summary: Owner can edit; everyone else can read.

Class	Read (4)	Write (2)	Execute (1)	Octal
Owner (u)				6
Group (g)				4
Others (o)				4

setuid (4) setgid (2) sticky bit (1)

Octal

Symbolic

Target File / Path

-R Recursive -v Verbose

644

rw-r--r--

Owner: read/write · Group: read · Others: read

chmod 644 filename

Low Risk Any user can read this file — never use it for secrets such as keys or .env files.

View the full chmod 644 guide →

chmod 644 Breakdown

Class	Digit	Symbolic	On a file	On a directory
Owner (u)	`6`	`rw-`	Read and write	Can list names, cannot enter
Group (g)	`4`	`r--`	Read only	Can list names, but not enter
Others (o)	`4`	`r--`	Read only	Can list names, but not enter

Is chmod 644 Safe?

Low Risk

Any user can read this file — never use it for secrets such as keys or .env files.

When not to use it

SSH private keys, .env credentials, and executable shell scripts

Common Use Cases

Web server assets including HTML, CSS, JavaScript, and PHP files
General configuration files without credentials
SSH public keys such as ~/.ssh/id_ed25519.pub

chmod 644 Command Examples

# Apply using octal mode
chmod 644 filename

# Apply using equivalent symbolic mode
chmod u=rw,g=r,o=r filename

# Recursive command warning:
chmod -R 644 /path/to/dir
# Note: -R applies the same mode to files and directories. Use find to treat them separately:
find /path/to/dir -type f -exec chmod 644 {} +

# Verify permissions
stat -c '%a %A %n' filename    # Linux
stat -f '%Lp %Sp %N' filename   # macOS

# Example ls -l output:
-rw-r--r-- 1 alice staff 1024 Jan 15 10:00 example.txt

umask Relationship

A umask of 133 makes new directories 644 and new files 644. Test umask values with our interactive Umask Calculator.

Frequently Asked Questions

What does chmod 644 mean?

Owner can edit; everyone else can read. In octal notation, the owner receives 6 (read/write), the group receives 4 (read), and others receive 4 (read).

Is chmod 644 safe?

chmod 644 is classified as Low Risk. Any user can read this file — never use it for secrets such as keys or .env files.

What is chmod 644 in symbolic notation?

In symbolic notation, chmod 644 is represented as rw-r--r--. You can apply this permission using the equivalent symbolic command "chmod u=rw,g=r,o=r filename".

Why is 644 the default for files?

In Unix multi-user architecture, files are designed to be readable by system utilities and background daemons while remaining protected from unintended modification. Mode 644 permits the owner to edit the file while allowing other processes to read it. It is the safe default produced by a standard 022 umask for newly created files.