Calculadora chmod

755 gives the owner full access and everyone else read and execute, used for directories and scripts. 644 gives the owner read and write and everyone else read only, used for normal files.

777 grants read, write and execute to everyone. It is almost always unsafe on a server because any user can modify the file. Prefer 755 or 644 instead.

Add the execute bit. From 644 you would move to 755 (or chmod +x), which turns on execute for owner, group and others.

Octal (like 755) encodes the permissions as numbers, while symbolic (rwxr-xr-x or u+x) describes them as letters. This tool shows both and keeps them in sync.

They are a fourth leading digit. Setuid and setgid run a program as its owner or group, and the sticky bit on a directory stops users deleting each other's files (as on /tmp).

When setuid, setgid or the sticky bit is set, the execute position is shown as s or t instead of x to signal the special bit is active.