Split View not working on your Mac? The usual causes

Split View is simple when it works and silent when it does not. These are the causes worth checking, in order.

1. Separate Spaces is off

Open System Settings, Desktop & Dock, and scroll to Mission Control. Displays have separate Spaces must be on for Split View. Changing it needs you to log out and back in.

2. The app cannot go that narrow

Every window has a smallest size. If an app cannot shrink to half your screen, macOS will not offer it as the second tile. This is common on 13 inch laptops with apps that have wide sidebars.

3. The window is not a normal window

Panels, palettes, dialogs and some settings windows cannot go full screen, so they cannot tile either.

4. Stage Manager is getting in the way

With Stage Manager on, Split View still works, but the window you pick may land in a different stage than you expect. Turn Stage Manager off in Control Centre to test.

When it still will not split

Desktop tiling in macOS 15 (drag to an edge) has fewer rules, because it does not need full screen. And a window manager that keeps windows side by side all the time sidesteps the question. ClutterFreeMac learns each app's smallest width and gives it room instead of overlapping it, so a wide app simply takes a wider column.