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Unix Permissions Converter

Convert between numeric and symbolic Unix file permissions with interactive toggles.

Permission Matrix

CategoryRead (4)Write (2)Execute (1)OctalSymbolic
Owner (u)6rw-
Group (g)4r--
Others (o)4r--

Enter Numeric Permission

Numeric (Octal)
644
Symbolic
rw-r--r--
ls -l Style
-rw-r--r--
chmod Command
chmod 644 filename

Common Permission Presets

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Frequently Asked Questions

What are Unix file permissions?
Unix file permissions control who can read, write, and execute a file. Every file has three sets of permissions: owner (the user who owns the file), group (users in the file's group), and others (everyone else). Each set can have read (r), write (w), and execute (x) permissions, represented as a 9-character string like rwxr-xr-x or a 3-digit octal number like 755.
How does numeric (octal) notation work?
Each permission has a numeric value: read=4, write=2, execute=1. These are summed for each category. For example, 755 means: owner has 7 (4+2+1 = rwx), group has 5 (4+0+1 = r-x), others have 5 (4+0+1 = r-x). Common values include 644 (rw-r--r--) for regular files and 755 (rwxr-xr-x) for executable files and directories.
What does chmod do?
chmod (change mode) is the Unix/Linux command used to change file permissions. It accepts both numeric notation (chmod 755 file.sh) and symbolic notation (chmod u+x file.sh). The -R flag applies permissions recursively to directories and their contents. Only the file owner or root user can change file permissions.
What is the difference between 644 and 755?
644 (rw-r--r--) allows the owner to read and write, while group and others can only read. This is the standard permission for regular files like HTML, CSS, and configuration files. 755 (rwxr-xr-x) adds execute permission for everyone, which is required for shell scripts, compiled programs, and directories (execute permission on a directory allows listing its contents).
Why does a directory need execute permission?
For directories, execute permission has a special meaning: it allows users to access (traverse) the directory and its contents. Without execute permission on a directory, you cannot cd into it, list its contents with ls, or access any files within it — even if you have read permission on the directory or the files inside. This is why directories typically need 755 permissions.
What is the sticky bit?
The sticky bit (octal 1000, shown as t in the execute position for others) prevents users from deleting or renaming files owned by other users in a shared directory. The classic example is /tmp, which has permissions 1777 (drwxrwxrwt). Everyone can create files in /tmp, but only the file owner can delete their own files.

How to Use the Unix Permissions Converter

Unix file permissions are a critical security concept that every developer and system administrator must understand. Our interactive converter makes it easy to translate between the three common permission formats: numeric (octal) notation like 644, symbolic notation like rw-r--r--, and the ls-style output like -rw-r--r-- that you see when running ls -l in the terminal.

Visual checkboxes: Use the interactive permission matrix to set read, write, and execute permissions for the owner, group, and others. The numeric value, symbolic string, and chmod command update instantly as you toggle each permission.

Numeric input: Enter an octal permission number like 644 or 755 and see the corresponding symbolic representation and permission breakdown. The visual checkboxes update to reflect the entered permissions.

Chmod command: The tool generates the complete chmod command you need to apply the selected permissions. Copy the command directly into your terminal or deployment script.

Understanding Unix Permission Model

The Unix permission model is elegant in its simplicity. Every file and directory has an owner (user), a group, and a set of permissions for three categories: the owner, the group members, and everyone else (others/world). Each category can independently have read (r=4), write (w=2), and execute (x=1) permissions.

The numeric (octal) notation represents permissions as a three-digit number where each digit is the sum of the permission values for that category. A digit of 7 (4+2+1) means full read+write+execute access. A digit of 6 (4+2) means read+write but no execute. A digit of 5 (4+1) means read+execute but no write. A digit of 4 means read-only.

Common Permission Patterns

644 (rw-r--r--): The standard permission for regular files. The owner can read and modify the file, while everyone else can only read it. This is appropriate for web content (HTML, CSS, JS), configuration files, and data files. Using 644 prevents unauthorized modification while allowing the web server to serve the files.

755 (rwxr-xr-x): The standard permission for executable files and directories. The owner has full control, while group and others can read and execute. Scripts, compiled programs, and directory structures typically need 755. For web servers, public directories like document roots use 755 so the server process can traverse them.

600 (rw-------): Restrictive permission for sensitive files. Only the owner can read and write; no one else has any access. Use this for SSH private keys (~/.ssh/id_rsa), environment files with secrets, and any file containing passwords or API keys. SSH will refuse to use a private key file with permissions more permissive than 600.

700 (rwx------): Restrictive permission for directories containing sensitive data. Only the owner can access the directory and its contents. Used for ~/.ssh directories, private configuration directories, and any directory that should be completely private to one user.

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