How to lock the Dock without installing anything

The four commands

Open Terminal from Applications, then Utilities, and run the ones you want:

defaults write com.apple.dock size-immutable -bool true; killall Dock
defaults write com.apple.dock position-immutable -bool true; killall Dock
defaults write com.apple.dock contents-immutable -bool true; killall Dock
defaults write com.apple.dock autohide-immutable -bool true; killall Dock

Size, position (which edge), contents (the icons) and hide and show. These write to your own account, so they need no administrator rights, and they survive a restart.

Check that it worked

defaults read com.apple.dock size-immutable

It answers 1 when the lock is on. Then open System Settings, Desktop & Dock: the locked control is grayed out and the divider no longer drags.

Undo it

Swap true for false, or delete the key and the Dock goes back to normal:

defaults delete com.apple.dock size-immutable; killall Dock

If a control is grayed out and you do not remember locking it, here is how to tell a lock from a managed profile.

What stops this from working

• Terminal is blocked. Some managed Macs hide it. Ask your IT team for the Dock settings they can push as a profile, which is the version that holds.
• The Dock resets at login. School and lab Macs often restore a saved image at sign-in. Anything you change is gone the next morning. See locking the Dock on a classroom Mac.
• Anyone with Terminal can undo it. These locks stop accidents. They do not stop a person who knows the command.
• The Dock jumps between screens. No command pins the Dock to one display. The options are here.

If you can install an app later

The same four locks are switches in Still Dock's menu bar, with Touch ID to unlock and a memory of the Dock you had before you locked it. Locking the size is free. The ways to lock a Dock, side by side, are in three ways to lock the Mac Dock.

Common questions

Do I need to be an administrator?

No. These settings belong to your own account, so a standard user can set and undo them.

Will my IT department see this?

The commands change only your own Dock preferences. They do not install anything and they do not touch the Mac's managed settings.

Does it work on macOS 26?

Yes. The four keys are unchanged. Only the settings panel moved, as covered in how to lock the Dock on macOS 26.