What do 755 and 644 mean?

Each digit is read(4) + write(2) + execute(1), for owner, group and others in order. 755 = rwxr-xr-x: owner full, others read and execute, typical for directories and scripts. 644 = rw-r--r--: owner read/write, others read-only, typical for regular and web files.

Why should I avoid 777?

777 lets any user on the system modify, delete or replace the file, and a 777 web directory is an easy target for injected scripts. Use 755 for directories and 644 for files, and fix ownership instead of opening permissions when something needs write access.

What is the s in rwsr-xr-x?

s means SetUID (owner position) or SetGID (group position): the program runs as the file's owner or group, e.g. passwd is 4755. A capital S means the special bit is set without execute permission. t is the sticky bit, as on /tmp (1777).

No. Everything runs locally in your browser with no network upload and is discarded when you close the page, so it is safe for internal or sensitive data.

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🔐Chmod Calculator - Linux File Permissions 755 / rwxr-xr-x Converter

Deploying a site, setting up SSH keys or writing shell scripts all involve Linux file permissions, and it is easy to forget what 755 or 644 actually mean. Tick read (r=4), write (w=2) and execute (x=1) for the owner (u), group (g) and others (o) and the tool shows the octal number and the symbolic form you see in ls -l; you can also type 750 or rw-r----- to parse it the other way. SetUID, SetGID and the sticky bit (e.g. 4755, 1777) are supported, and ready-to-copy chmod commands are generated in both numeric and u=,g=,o= forms with optional -R. Thirteen common permission presets are listed with their typical use.

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How to use Chmod Calculator

1Tick read, write and execute for each role, or type an octal or symbolic permission
2Optionally set SetUID, SetGID or sticky, enter a file name and choose recursive
3Copy the generated chmod command, or click a common preset

FAQ

What do 755 and 644 mean?: Each digit is read(4) + write(2) + execute(1), for owner, group and others in order. 755 = rwxr-xr-x: owner full, others read and execute, typical for directories and scripts. 644 = rw-r--r--: owner read/write, others read-only, typical for regular and web files.
Why should I avoid 777?: 777 lets any user on the system modify, delete or replace the file, and a 777 web directory is an easy target for injected scripts. Use 755 for directories and 644 for files, and fix ownership instead of opening permissions when something needs write access.
What is the s in rwsr-xr-x?: s means SetUID (owner position) or SetGID (group position): the program runs as the file's owner or group, e.g. passwd is 4755. A capital S means the special bit is set without execute permission. t is the sticky bit, as on /tmp (1777).
Is my data uploaded?: No. Everything runs locally in your browser with no network upload and is discarded when you close the page, so it is safe for internal or sensitive data.