chmod calculator: Linux file permissions made easy
Need a Linux server to practise on? Get one on Kvantis →
How chmod numbers work
Each digit is the sum of three flags: 4 = read, 2 = write, 1 = execute. The first digit is for the file's owner, the second for its group, the third for everyone else. So 754 means owner rwx (4+2+1), group r-x (4+1), others r-- (4).
Permissions you'll use 95% of the time
| Mode | Use it for |
|---|---|
644 | Normal files: web pages, images, most configs |
755 | Directories and executable scripts |
600 | SSH private keys, .env files with passwords |
700 | The ~/.ssh folder and other private directories |
chmod 600 ~/.ssh/id_ed25519 and chmod 700 ~/.ssh.Apply to a whole folder with chmod -R — but careful: chmod -R 755 also makes every file executable. Use find /path -type f -exec chmod 644 {} + for files and -type d with 755 for folders.
FAQ
What does chmod 777 do?
It lets every user on the server read, change and execute the file. It is almost never needed and is a common cause of hacked websites. Use 755 for folders and 644 for files instead.
What is the difference between 644 and 755?
755 adds execute permission for everyone. Directories need it to be opened; scripts need it to be run. Plain files should usually be 644.
Why does SSH reject my key?
Private keys must be readable only by you: chmod 600 for the key file and chmod 700 for the ~/.ssh folder.
Deploy a VPS on Kvantis
Hourly billing, paid in crypto, no KYC. Your server is live in about a minute.
- Plans from $10/month + VAT, billed per hour — destroy anytime
- 32 locations worldwide, IPv4 + IPv6, full root
- BTC, ETH, USDT, USDC, LTC and 30+ coins; just an email to sign up
Disclosure: Kvnthost is run by the team behind Kvantis.