Chmod Calculator
Visually configure Unix/Linux file permissions. Instantly translate between checkboxes, octal numbers (e.g. 755), and symbolic strings (e.g. rwxr-xr-x).
How to Use
- Click the checkboxes under Owner, Group, and Public to visually build your desired permission set. The outputs on the right will update in real-time.
- Alternatively, if you found a command on StackOverflow (like
chmod 644) and want to know what it actually does, type644directly into the Octal Format box. The checkboxes will automatically sync to show you exactly who has read, write, and execute access. - Click the copy icon next to the Linux Command to grab the perfectly formatted terminal string.
Features
Two-Way Sync
Type the octal number to update the checkboxes, or click the checkboxes to generate the octal number.
Symbolic Parsing
Instantly translates complex symbolic strings (like rwxr-x---) into readable UI checkboxes.
Command Ready
Generates the exact syntax needed for your Ubuntu, Debian, or CentOS terminal.
Privacy Protected
Zero server uploads. The mathematical translation engine runs locally on your browser.
Understanding Unix File Permissions
Every file and directory on a Linux or Unix-based operating system has strict access rights. These rights are divided into three specific classes of users:
- Owner: The user who created the file. They typically have the most access.
- Group: Other users who share the same group as the owner.
- Public (Other): Every other user on the system (the general public).
Each of these classes can be granted three specific permissions:
- Read (r): The mathematical value is 4. Allows the user to open and view the file's contents.
- Write (w): The mathematical value is 2. Allows the user to edit, modify, or delete the file.
- Execute (x): The mathematical value is 1. Allows the user to run the file as a program or script.
By adding these mathematical values together, you get the Octal number. For example, if the Owner has Read (4), Write (2), and Execute (1), their total is 7. If the Public only has Read (4) and Execute (1), their total is 5. Thus, 755 is born!
The Developer Toolkit
If you are managing a Linux web server, ensure your cryptographic passwords are secure using our Password Generator and hash them using the Bcrypt Generator. If you need to convert Unix timestamps found in your server logs into human-readable dates, use the Unix Timestamp Converter.
Frequently Asked Questions
What does chmod 777 mean?
chmod 777 grants Read (4), Write (2), and Execute (1) permissions to absolutely everyone: the Owner, the Group, and the Public. This is highly dangerous on a web server because it allows any malicious user to edit or delete your files. Use it with extreme caution.
What are the best permissions for a web server?
For a standard Apache or Nginx web server, the industry standard is 644 for files (Owner can read/write, everyone else can only read) and 755 for directories (Owner can read/write/execute, everyone else can read/execute).
Why do directories need the Execute permission?
In Unix, the "Execute" permission on a directory does not mean you can run the directory as a program. Instead, it grants the user permission to enter the directory (e.g., using the cd command) and access the files inside it.
Is it free?
Yes, 100% free with no limits.