Binding an app to 2nd monitor

I have a 27" iMac and a second display extending my desktop. There are apps that I use occasionally and briefly during the day (Messages, Contacts, 1Password), and I like to have their windows on the 2nd display while I do my main work on the primary display. When I launch apps, some seem to know that I want them on display #2 (e.g. Address Book) and always open there. Others (Messages, 1Password) always open on the primary display.

I have tried various things to get apps to bind to display #2 (e.g. open them with the desktop active on that display, make sure the app is on that display and in the foreground when I quit) to no avail.

Anybody know a technique for binding the app to a specific display when you launch it?

Nick Pappas

When you have defined multiple desktops (done implicitly with multiple displays), it is easy to fix an app to a particular desktop. WIth the application foregrounded, go to the dock and control-click on the dock icon for the app. Select the ‘Options’ item and choose “This Desktop” as the “Assign to” option.

I actually don’t use this for multiple monitors, but have multiple desktops assigned to separate my email, browser, iTunes, and general workspace desktops. I use a 4-finger swipe gesture on the trackpad to move from one to another.

Exactly as @aforkosh says. If you want some more flexibility you can use an app like Moom to move windows around with keystrokes.

I had never noticed that option. Thanks

What OS does that start in, I don’t see it in Sierra.


The option to fix an app to a particular (desktop) space has been there ever since OS X supported Spaces, later simplified to Mission Control. I was never able to get my head around Spaces, but when they simplified it, I understood. According to, Spaces support was introduced with OSX 10.5 (Leopard) in 2006 and was superseded by Mission Control with OS 10.7 (Lion).

Ok thanks - the obvious reason then is because I’m not plugged into my external monitor. I’ll try it later, thanks for the tip!


Is this gone from Mojave? I do not see “This Desktop” or “Assign to” (even after trying tons of different key combination).

Also, can you do this for Finder, as well? I love running with two monitors, but I never know which monitor is going to host a particular app/window or the Command-Tab app switcher, and I want everything to appear on my primary monitor unless I say otherwise.

It’s there. As long as the application is in the Dock, you can play with the ‘Assign to’ option. So the application does not need to be in the foreground (or even running if it is permanently in the Dock). Remember that the ‘Assign to’ option doesn’t show up directly but is under the ‘Options’ command. Note that the possible assignments are ‘All Desktops’, ’This [the current] Desktop”, “None”, and if a current specific assignment exists, the desktop to which the application is currently assigned.

Thanks Alan. Gad I feel like a noob here, but I don’t see it. And I’m even wearing my new glasses!
Here’s an example of what I’m seeing:

Those appear to be all my options for all app icons in my dock. What am I missing?

I did a search on 'mac dock options "assign To” missing’. I didn’t see anything Mojave specific, but did see some folks saying the temporarily adding a ne Space via Mission Control would revive it.

Tada! Yes, I created a new Space and these options are now available. Thank you!

Just a note on why this worked:

Another solution I saw indicated that the cause was corruption in 1 or 2 preference files and recommended deleting them so that the system woulod create fresh ones. I think that the act of manipulating the number of spaces effectively forced a rewrite of the corrupted files and solved the problem.