AltTab
The window switcher Apple should have built
AltTab shows every window across every space in one switcher — minimized, fullscreen, off-display.
An open-source ⌥-Tab window switcher for macOS that shows live thumbnails of every window across every space. Apple’s ⌘-Tab switches between apps; AltTab fills the obvious gap by switching between windows.
The default ⌥-Tab binding is unused on macOS, so AltTab slips in without conflict. Hold the modifier, scrub through full thumbnails with the keys or trackpad, release on the one you want. Defaults are correct for most people — minimized windows, multiple displays, fullscreen apps — but every behavior is a preference if you want it.
Sits in the menu bar at near-zero idle CPU and only wakes when invoked. Free, GPL-licensed, macOS 11+.