How macOS actually works

Permissions without the jargon

Updated 2026-07-31 · 4 min read

The rwxr-xr-x string is less cryptic than it looks, and understanding it fixes most 'permission denied' moments.

Reading the string

-rwxr-xr-x

• First character: - file, d directory, l symlink
• Then three groups of three: owner, group, everyone else
• In each group: r read, w write, x execute (or, for folders, "enter")

So rwxr-xr-x = owner can do everything; group and others can read and enter but not change.

The numbers

Each group is a digit, summing r=4, w=2, x=1:

• 755 = rwxr-xr-x (owner full, others read+enter) — the normal folder
• 644 = rw-r--r-- (owner read/write, others read) — the normal file
• 700 = private to you
• 777 = everyone can do anything — almost always a mistake

The fixes you will actually use

chmod u+w file            # give yourself write
chmod 644 file            # standard file
chmod 755 folder          # standard folder
chmod -R u+rw folder      # fix a whole tree you own
sudo chown -R "$(whoami)" folder    # take ownership after a migration

Files vs folders differ

A folder needs x (execute) to be entered, even just to list it — which is why 644 on a folder locks you out and 755 is the folder norm. Apply the two correctly across a tree:

find folder -type d -exec chmod 755 {} \;
find folder -type f -exec chmod 644 {} \;

When it is not permissions

Two things masquerade as permission problems: SIP (system paths, unfixable by design) and TCC/Full Disk Access (personal data, fixed by granting the app access, not by chmod). If chmod does not help, it is probably one of those — the permissions article and the Full Disk Access article cover each.

Common questions

What does chmod 755 mean?

Owner can read, write and execute; group and everyone can read and execute (enter, for folders) but not write. The standard folder permission.

Why can I read a file but not a folder with the same permissions?

Folders need execute (x) to be entered. 644 works for a file but locks a folder; 755 is the folder equivalent.