What does chmod 755 mean?

chmod 755 grants the owner full read, write, and execute permissions (7 = 4+2+1), while the group and others get read and execute permissions but not write (5 = 4+0+1). It is the standard permission for web server directories and executable scripts.

What is the difference between numeric and symbolic chmod formats?

Numeric (octal) format uses three digits (e.g. 755) where each digit is the sum of read (4), write (2), and execute (1) for owner, group, and others respectively. Symbolic format (e.g. rwxr-xr-x) spells out each bit explicitly with letters — r for read, w for write, x for execute, and - for no permission.

What chmod value should I use for a web server file?

For regular web files (HTML, CSS, JS, PHP), use 644 (owner can read/write, everyone else can read). For directories, use 755 (owner can read/write/enter, everyone else can read/enter). Never use 777 in production — it grants write access to all users on the system.

What does chmod 600 mean and when should I use it?

chmod 600 gives the owner read and write access only — no group or other permissions at all. Use this for sensitive files like SSH private keys (~/.ssh/id_rsa) and configuration files with passwords. SSH will actually refuse to use a private key unless it has 600 or 400 permissions.

How do I apply chmod recursively to all files in a directory?

Use the -R flag: chmod -R 755 /path/to/directory. Be careful with recursive chmod — it applies the same permission to both files and directories. A common pattern is to use find to apply different permissions: find /path -type f -exec chmod 644 {} \; for files and find /path -type d -exec chmod 755 {} \; for directories.

What is the sticky bit, setuid, and setgid in chmod?

These are special permission bits represented by a leading digit in a 4-digit octal value. Setuid (4xxx) runs an executable as its owner. Setgid (2xxx) runs it as its group, or makes new files in a directory inherit the group. Sticky bit (1xxx) on a directory prevents users from deleting files they don't own (used on /tmp). Example: chmod 1777 /tmp sets the sticky bit plus full rwx for everyone.

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Stop guessing chmod values. Set permissions with checkboxes, enter numeric codes, or pick a preset — and instantly see the numeric value, symbolic notation, and ready-to-run chmod command.

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Toggle any permission bit and see the numeric code and symbolic notation update in real-time. No page reloads, no servers.

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Type a numeric value like 755 and the checkboxes snap to match, or click checkboxes and watch the number update instantly.

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Unix Permission Builder

File type:

Owner

readwriteexecute

Group

readwriteexecute

Other

readwriteexecute

Numeric (octal)

Symbolic

-rwxr-xr-x

Command

$ chmod 755 filename

Common presets

r = Read (4)w = Write (2)x = Execute (1)- = No permission (0)Digit = r+w+x sum per group

Frequently Asked Questions

Everything you need to know about Chmod Calculator.

Calculate Unix PermissionsVisually

Instant Conversion

Bidirectional Input

Ready-to-Run Commands

Unix Permission Builder

Frequently Asked Questions

Calculate Unix Permissions
Visually