Three ways to lock the Mac Dock, compared

The three ways

1. Terminal

Four commands, one per lock:

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

The others are position-immutable, contents-immutable and autohide-immutable. The full guide covers all four, including the fifth one people repeat that does nothing.

Good when: it is your own Mac, you know what you want, and you will not need to change it often.

The catches. Each lock is a separate command with an exact key name, and a typo fails silently with no error. Changing your mind means going back to Terminal. Nothing records what your Dock looked like before, so if you lock it at the wrong size there is nothing to return to. And System Settings goes grey with a message about a profile, which is confusing enough that people search for what went wrong months later.

2. A configuration profile

A profile is what organisations use to manage Macs. It sits above user preferences, so it holds when a preference would not.

Good when: other people use the Mac. A front desk, a classroom, a shop display, a shared family machine.

The catches. You have to write the profile XML or use something that generates it. macOS asks you to approve each one. And it is deliberately harder to remove, which is the point but also the risk: it outlives the thing that installed it, so it must be removed on purpose in System Settings, General, Device Management.

3. An app

An app sets the same macOS settings, with switches instead of commands.

Good when: you want to see what is locked, change it without looking anything up, and get your original setup back.

The catches. It costs money, and it is another thing running. What you get for that is visibility and reversibility: which locks are on, one click to change them, and a snapshot of the Dock you had before you locked it.

Still Dock is ours, and it is the app-shaped way to lock the Mac Dock. It does the four locks, adds a display pin and a Cmd Q guard that Terminal cannot do at all, and can install the profiles from point 2 without you writing XML.

Which one to pick

• Your own Mac, set once, comfortable in Terminal. Use Terminal. Genuinely, it is free and it works. Write down what you ran.
• Your own Mac, you expect to adjust it. An app, because the retyping is what wears people down.
• A Mac other people use. A profile. Nothing else survives contact.
• A managed fleet. Your MDM, centrally. Do not do this machine by machine.

Using more than one screen? The Dock also jumps between them, which is a separate problem with its own fixes: how to keep the Mac Dock on one screen.

Common questions

Do these conflict if I use more than one?

A profile wins over a Terminal setting. If your settings are greyed out and undoing the commands changes nothing, look for a profile.

Is the app doing anything Terminal cannot?

For the four locks, no, and we say so on the home page. Pinning the Dock to one display and guarding Cmd Q are different mechanisms with no Terminal equivalent.

Will any of this survive a macOS update?

The preferences and profiles normally carry across. Apple can change Dock behaviour in any release, which is true of all three approaches equally.

What is the free way to try before deciding?

Run the size command. If freezing the size fixes your problem you may need nothing else. If you find yourself undoing and redoing it, that is your answer.