macOS has built-in window tiling, so you no longer need a third-party app just to put two windows side by side. Golden Gate also improves how window positions persist across external displays.
1Tile by dragging
Drag a window to the left or right edge of the screen to fill that half, or to a corner to fill a quarter. Drag it to the top edge to fill the screen. Hold Option while dragging to see the tile outline immediately.
2Tile from the menu or keyboard
Hover over the green button in a window's top-left corner, or use Window > Move & Resize, to choose a layout such as Left & Right or Quarters. The keyboard shortcuts are listed in that menu and use the Globe (Fn) and Control keys with the arrow keys, for example Fn+Control+← for the left half. To restore a window, choose Return to Previous Size.
3Tiling options
In System Settings > Desktop & Dock, under Windows, you can turn edge tiling and Option-drag tiling on or off and choose whether tiled windows have margins between them.
4Stage Manager and full screen
Stage Manager (in Control Centre) groups the windows you're using in the middle and lines up other apps on the left. Full screen (Fn+F or the green button) gives an app its own Space; drag a second window onto it in Mission Control for split view.
5Small tweaks that help
Change scroll direction, tracking speed and gestures in System Settings > Trackpad and Mouse.
Turn on three-finger drag in System Settings > Accessibility > Pointer Control > Trackpad Options.
Set Hot Corners in Desktop & Dock (for example, bottom right to lock the screen).
In the Finder, choose View > Show Path Bar and Show Status Bar.
In Keyboard settings, raise Key repeat rate and shorten Delay until repeat.