chmod 664 Permission Explained: Group-Writable File

Octal

664

Symbolic

rw-rw-r--

Binary

110 110 100

Risk Level

Moderate

Summary: Owner and group can edit; others read.

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

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

Octal

Symbolic

Target File / Path

-R Recursive -v Verbose

664

rw-rw-r--

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

chmod 664 filename

Moderate Every member of the group can modify this file.

View the full chmod 664 guide →

chmod 664 Breakdown

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

Is chmod 664 Safe?

Moderate

Every member of the group can modify this file.
Any user can read this file — never use it for secrets such as keys or .env files.

When not to use it

Configuration files storing secrets, passwords, or single-user environments

Common Use Cases

Collaborative source files and shared git checkouts in multi-user teams
Shared data files edited by developers belonging to the same Unix group

chmod 664 Command Examples

# Apply using octal mode
chmod 664 filename

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

# Recursive command warning:
chmod -R 664 /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 664 {} +

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

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

umask Relationship

A umask of 113 makes new directories 664 and new files 664. Test umask values with our interactive Umask Calculator.

Frequently Asked Questions

What does chmod 664 mean?

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

Is chmod 664 safe?

chmod 664 is classified as Moderate. Every member of the group can modify this file.

What is chmod 664 in symbolic notation?

In symbolic notation, chmod 664 is represented as rw-rw-r--. You can apply this permission using the equivalent symbolic command "chmod u=rw,g=rw,o=r filename".

Related Permissions

Change one bit:

chmod 264 remove owner read chmod 464 remove owner write chmod 764 add owner execute chmod 624 remove group read chmod 644 remove group write chmod 674 add group execute chmod 660 remove others read chmod 666 add others write chmod 665 add others execute

Often compared: chmod 644 vs 664

← chmod 663 chmod 665 →

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