DockAltTab

Window previews for the macOS Dock, built directly on top of AltTab.

Hover a Dock icon and its windows pop up right above it; the AltTab switcher (⌥⇥ by default) is still there too.

This used to be two apps: a DockAltTab companion that drove a "scriptable" fork of AltTab through AppleScript. This repository merges them — the DockAltTab behaviour now lives inside the AltTab codebase (see src/DockAltTab), so there is no companion app and no AppleScript round-trip. Everything AltTab does (the switcher, the settings window, Sparkle updates, …) is still included.

Website: https://dockalttab.netlify.app

What it does

• Dock hover previews — hover any Dock app icon to see its windows, positioned and clipped relative to the icon (magnification- and edge-aware).
• Thumbnail previews — hover a window thumbnail to get a large preview of that window; the delay is configurable.
• No unwanted Space switching — clicking a Dock icon in the click-driven modes is handled by DockAltTab, so activating an app whose windows live on another Space unhides it first and only activates once it is visible, instead of triggering a Space swoosh.
• The full AltTab switcher and settings remain available.

Modes

DockAltTab has three interaction styles, selectable in its preferences:

Mode	Hover a Dock icon	Left-click a Dock icon	Middle-click a Dock icon
MacOS	show previews	native Dock behaviour	native Dock behaviour
Windows	show previews	non-frontmost app → activate it; frontmost app → hide it	—
Ubuntu	—	non-frontmost app → activate it; frontmost app with ≥2 windows → toggle previews; otherwise → hide it	show previews (if the app has ≥1 window)

In every mode, a click that DockAltTab acts on is swallowed, so the native Dock cannot also fire a Space switch.

Preferences

The menu-bar menu has a DockAltTab item (first in the list) that opens the DockAltTab Preferences window. It contains the Preview Settings:

• Mode — MacOS / Windows / Ubuntu
• Show Delay — delay before previews appear when hovering an icon
• Hide Delay — delay before previews disappear when leaving
• Thumbnail Preview Delay — delay before a hovered thumbnail expands
• Enable Thumbnail Previews
• Reposition preview after dock magnification — follow the icon while the Dock magnification animation settles
• Preview Distance — gap between the previews and the Dock
• Keep dock showing during previews — keep an auto-hiding Dock visible while previewing

The DockAltTab menu-bar icon (a DockAltTab logo) is the default; the other AltTab icons remain selectable under Settings → General → Menubar icon.

Permissions

• Accessibility — required (global event taps + Accessibility queries of the Dock and windows).
• Screen Recording — required for window thumbnails.

On first launch the app requests them; grant them in System Settings and relaunch.

Install / build

Build from source with Xcode (the workspace includes the CocoaPods dependencies):

# from the repository root
xcodebuild -workspace alt-tab-macos.xcworkspace -scheme Debug -configuration Debug build

Or open alt-tab-macos.xcworkspace in Xcode and run the Debug scheme. The product is DockAltTab.app.

CocoaPods are vendored under Pods/, so a separate pod install is normally not required.

Scripting

The app is scriptable (this comes from the scriptable AltTab fork). The dictionary is in DockAltTab.sdef.

Basic commands

• hide — hide the overlay/UI.
• show — show all app windows (the regular AltTab shortcut).
• showApp — show a specific app's windows (ignores the blacklist).
  • appBID — bundle identifier of the app.
  • x / y (optional) — position of the Dock icon; resets on hide.
  • dockPos (optional) — bottom / left / right, helps position/clip the previews.
• trigger — go to the next window without showing the overlay.

Miscellaneous commands

• countWindows (appBID) — number of windows for an app, across all Spaces.
• countWindowsCurrentSpace (appBID) — number of windows for an app in the current Space.
• countMinimizedWindowsCurrentSpace (appBID) — number of minimized windows for an app in the current Space.
• countWindowStats (appBID) / countAllWindowStats — window-count records.
• deminimizeFirstMinimizedWindowFromCurrentSpace (appBID) — deminimize the app's first window minimized on the current Space.
• keyState (key) — whether a key is currently pressed.
• appSetting (named) — read a setting used for showApp previews (appsToShow, showHiddenWindows, showFullscreenWindows, showMinimizedWindows, spacesToShow, screensToShow, showTabsAsWindows).
• thumbnailPreview — show the large preview of the selected window.
• repositionThumbnails ({x, y}) — reposition the preview panel.

Example:

tell application "DockAltTab" to showApp appBID "com.apple.Safari"
tell application "DockAltTab" to showApp appBID "com.apple.Safari" x 0 y 0 dockPos "bottom"
tell application "DockAltTab" to hide

Internally, DockAltTab no longer needs these commands — it calls the same code directly — but they are kept for automation.

Notes / differences

• On launch, if the Dock's showhidden preference is off, DockAltTab enables it and restarts the Dock once (translucent icons for hidden apps).
• Some apps' windows are ignored by personal preference, e.g. BetterTouchTool "pinned"/floating windows and Screenhint floating windows.
• Preview button order: Exit first, Quit last.
• Fading is faster for DockAltTab previews (111 ms) than for regular previews (333 ms).
• Window controls auto-reopen after closing a window, so repeated clicks keep working.

Credits

DockAltTab is built on AltTab by Louis Pontoise and contributors, and on the "scriptable" fork by steventheworker. Both are licensed under GPL-3.0; see LICENCE.md.

Sister app: Dock Exposé.