chmod permission calculator
Tick read/write/execute for owner, group and others to get the octal (755) and symbolic (rwxr-xr-x) form, or parse an octal or symbolic mode back into checkboxes — with SUID/SGID/sticky bits and common presets.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Accepts 3 or 4 octal digits (755, 0755, 4755) and rwxr-xr-x, rwsr-xr-x, rwxrwxrwt — a leading type character such as drwxr-xr-x is ignored.
Permissions
Result
755 · rwxr-xr-x
7550755rwxr-xr-xchmod 755 index.html0 7 5 5What each permission means
| Bit | Regular file | Directory |
|---|---|---|
| r = 4 | View the contents of a file | List the file names in a directory |
| w = 2 | Modify or overwrite a file | Create, delete or rename entries in a directory |
| x = 1 | Run the file as a program | Enter the directory and access paths inside it |
| Applies to | Notes |
|---|---|
| Owner (u) | The file owner; first octal digit. |
| Group (g) | Members of the file group; second octal digit. |
| Others (o) | Everyone else; third octal digit. |
| Special bit | Notes |
|---|---|
| SUID (s) | Runs with the file owner privileges, e.g. /usr/bin/passwd. Shown as s in the owner slot. |
| SGID (s) | Runs with the file group privileges; on directories new files inherit the group. |
| Sticky (t) | Inside a directory only owners may delete or rename files, e.g. /tmp. Shown as t in the others slot. |
What this tool does
- The moment you see a chmod command you did not write: paste 755 or rwxr-xr-x and see exactly which bit grants read and which grants execute.
- Sanity-check permissions before deploying — directories usually need 755 to be enterable and plain files 644, so you never end up with a recursive 777.
- Debug why files in /tmp cannot be deleted or why new files in a shared directory get the wrong group by inspecting sticky and SGID modes such as 1777 and 2755.
- Copy the ticked result straight out as a ready command like chmod 755 index.html instead of adding digits in your head.
Example
Input
755
Output
Octal 755 (4-digit form 0755); symbolic rwxr-xr-x; digits: owner rwx (7), group r-x (5), others r-x (5); command chmod 755 index.html
Without special bits the octal form has three digits; ticking SUID/SGID/sticky makes it four, so 4755 shows up as rwsr-xr-x with the s in the owner slot.
Frequently asked questions
Which of 755, 644 and 777 should I use?
The three digits are owner, group and others, and 4=read, 2=write, 1=execute — add them up. Directories are usually 755 (enterable and listable), shared plain files 644, private files 600. 777 lets anyone modify the file and belongs only in temporary debugging.
What is the difference between s and S, or t and T?
Lowercase means the special bit is set together with the execute bit, uppercase means the special bit is set but execute is not. rwsr-xr-x is SUID with an executable owner, rwSr-xr-x is SUID without it — usually a leftover mistake.
What is the sticky bit (1777) for?
On a directory it means only the file owner (or root) may delete or rename entries inside — exactly how /tmp works: everybody can write, nobody can delete somebody else’s files. It is the leading octal 1 and shows as t in the others slot.
Why is 888 rejected as an invalid octal permission?
Each digit must be 0–7, so 8 is out of range. Symbolic input must be exactly nine characters such as rwxr-xr-x, optionally with a leading type letter (drwxr-xr-x); every other position must be rwx or a dash.
Does this apply to Windows permissions?
No. chmod belongs to the POSIX model used by Linux, macOS and BSD, while Windows uses ACLs and the two do not map onto each other. The tool only computes locally and never reads or changes real file permissions.
Keywords：chmod权限permissionoctal八进制755644rwxr-xr-xsuidsgidstickylinux 权限