Split
Side-by-side windows that resize together.
About Split
Split places windows into halves and custom ratios by shortcut or by dragging to a snap zone, then links the pair so one divider resizes both. It can swap sides and cycle through the windows stacked on each half.
Questions about Split
How much does Split cost?
Split is paid software, bought up front from splitformac.com.
Where can I download Split for Mac?
Download Split from the developer's website (splitformac.com). MacWorthy links only to official sources.
What are good alternatives to Split?
Other windows & desktop apps for Mac worth a look are Rectangle (open source), Magnet (one-time purchase), Moom (one-time purchase) and Loop (open source).
Other windows & desktop apps like Split
Rectangle
Window snapping with keyboard shortcuts.
Magnet
Snap windows into place by dragging.
Moom
Save and restore entire window layouts.
Loop
Window management with a radial menu.
Swish
Window control with trackpad gestures.
Tangrid
Automatic tiling with saved layouts per Space.
Resettle
Puts windows back when you reconnect your monitors.
AltTab
Windows-style alt-tab, with window previews.