chmod 666

rw-rw-rw-Dangerous — avoid on real systems

Everyone can read and write; nobody can execute.

666 gives every user read and write access, with no execute bit. Any account or process on the system can change or empty the file.

Linux uses it for device files that must be universally usable — /dev/null and /dev/zero are crw-rw-rw- — but for ordinary files it's rarely right.

Permission by permission

Who	Read	Write	Execute	Digit	Means
owner	✓	✓	—	6	read and write
group	✓	✓	—	6	read and write
others	✓	✓	—	6	read and write

In ls -l: -rw-rw-rw- for a file, drw-rw-rw- for a directory.
Symbolic form: u=rw,g=rw,o=rw
New files get this mode when the umask is 000.

Use it for

Device files and similar special cases that genuinely must be writable by all.

Avoid it for

Config files, logs and data — anyone could tamper with them. Use 644, or 664 with a shared group.
Upload targets on web servers.

Commands

chmod 666 path

set this mode on a file or directory

chmod u=rw,g=rw,o=rw path

the same, written symbolically

find path -type f -exec chmod 666 {} +

apply it to every file in a tree, leaving the directories alone

stat -c '%a %A %n' path

check the current mode on Linux (macOS: stat -f '%Lp %Sp %N' path)

Try variations

Mode — octal or ls -l form

666

-rw-rw-rw-

Who	read	write	execute	Digit
owner				6
group				6
others				6

setuid— run as the file's ownersetgid— run as / inherit the groupsticky— only owners delete entries

The owner can read and write; the group can read and write; everyone else can read and write.

chmod 666 file

chmod u=rw,g=rw,o=rw file

Read the full guide to chmod 666 →

Frequently asked questions

Is 666 safer than 777?

Slightly — it can't be executed directly — but anyone can still change the contents. A script with 666 could be modified by any user and then run by someone who trusts it.