AltTab

AltTab is a free, open-source window switcher for macOS that recreates the Windows Alt-Tab experience. Instead of cycling through applications, it lists every open window — including windows that are minimized, hidden, or sitting on another Space or monitor — each with a live thumbnail and a badge showing where it lives. The selected window is previewed full size before you commit, so you can confirm you are jumping to the right document.

The core switcher is free forever: switching between individual windows, previews before switching, and custom shortcuts. The optional AltTab Pro license adds search by window title or app name, extra switcher styles (app icons, compact title list), auto-sizing previews, and up to nine separate shortcuts. Pro is a one-time purchase with a 14-day trial, and the source for the whole app is published under GPL-3.0, so you can build it yourself.

Compared with paid macOS switchers such as Contexts and Witch, AltTab is free at the core and adds Space and monitor awareness plus trackpad gestures. It also coexists with the built-in Command-Tab switcher — AltTab uses Option-Tab by default, and you can remap it to Command-Tab if you want to replace the system switcher entirely. It requires macOS 12 or later and runs natively on Apple silicon and Intel.