Free (Open Source) Compatibility: macOS 10.15+ (Apple Silicon support via Homebrew)
AltTab does not touch the Dock. Instead, it replaces the awful macOS Cmd+Tab app switcher with an interface that looks exactly like Windows.
: Assign custom mouse and key shortcuts to Dock items to quickly open new windows, hide apps, or trigger Mission Control (Exposé). Installation & Compatibility Make your Mac More Like Windows 7 with HyperDock
David W. moved on to other tools. He once wrote in a final email to users:
The macOS Dock has long served as the central hub for application launching and basic window switching. However, historically, the operating system relied heavily on the Cmd+Tab keyboard shortcut or "Exposé" (now Mission Control) for navigating between multiple open windows. While functional, these methods often lacked visual immediacy or required multiple steps to identify specific document windows within a single application.
HyperDock has been around for a long time, and while some users worry about compatibility with the latest versions of macOS, it continues to be a remarkably stable tool with very low CPU usage. Hyperdock for Mac - Jay Holtslander
If you don't want to pay for software and just want a taste of window previews, there is a hidden native macOS feature. However, it only works within the app you are currently using.