The macOS Dock keeps jumping between displays. Here's why — and how to stop it.
If you run more than one monitor on a Mac, you've probably seen it: you click an app on your second display, and the Dock jumps over to meet you. Or you grab a window and the Dock disappears, only to reappear on whichever screen your cursor wanders to. It looks like a feature. In practice it's death by a thousand jumps.
There's also the resize trap. The Dock has a thin vertical divider between your running apps and the Recents / Files / Trash group. It's almost the same size as the icons next to it. Grab it by accident and you've stretched your Dock from cozy to comical. Move your cursor wrong and you've made it microscopic. macOS doesn't ask first. It just resizes.
These are two different problems with the same root: macOS treats the Dock as something to be moved around. DockLockr treats it as something to lock down.
Why the Dock moves between displays
The relevant setting lives in System Settings → Desktop & Dock → Mission Control → “Displays have separate Spaces”.
When this setting is off (its default), all your displays share one set of Spaces — and one Dock, which floats to whichever display you're actively using. macOS decides where the Dock should be based on where your cursor is and which display contains the frontmost app. The intent is “Dock follows you.” The reality is “Dock follows cursor on a hair-trigger.”
When the setting is on, each display gets its own Dock and its own Spaces. The Dock no longer jumps, because each display owns one. The cost: each display also has its own Spaces, which can scramble window- management muscle memory if you're used to a shared Space across screens. macOS also requires a logout to apply the change.
That's the native fix: a logout, a behavioral overhaul, and the loss of cross-screen Spaces.
The accidental-resize problem
Even after you've solved the screen-jump problem, the Dock divider is still there. On a horizontal Dock it sits between your last pinned app and the Recents / Files / Trash group. On a vertical Dock it's near the bottom. Drag it and the Dock resizes.
There's no confirmation, no haptic feedback, no “are you sure?” prompt. You can't disable the behavior in System Settings. The only mitigation Apple ships is right-clicking the divider to pick a fixed size — which doesn't help once you've already resized by accident, and doesn't prevent it from happening again ten minutes later.
What DockLockr does about it
DockLockr lives in your menu bar as a small lock icon and gives you three switches:
- Lock Dock Items. Stops anything being added, removed, or rearranged. Your layout stays your layout.
- Lock Dock Size. Pins the magnification and size. The divider becomes inert — dragging it does nothing.
- Pin Dock to Screen. Keeps the Dock on the display you chose, even when Displays have separate Spaces is off. You get a static Dock without giving up your cross-screen Spaces.
Each switch is independent — flip the one you need, leave the rest. When you quit DockLockr, the Dock unlocks cleanly; it never leaves your Dock frozen. And a one-click Reset Dock is one menu item away if you ever want to start over.
The point of DockLockr isn't to disagree with macOS. It's to give you a single, reversible toggle for behavior that Apple otherwise makes you either accept or restructure around.