AppUserModelID (AUMID)
The Windows app identity string that controls taskbar grouping and toast notifications - and why Electron apps break without it.
AppX / MSIX (Microsoft Store package)
The Windows packaging format for Microsoft Store distribution - how it differs from a classic .exe installer.
Code Signing
What code signing is, why unsigned apps trigger security warnings, and what it takes to sign for macOS and Windows.
DMG (Apple Disk Image)
The .dmg format Mac apps ship in - why the drag-to-Applications ritual exists and what a proper DMG needs.
Gatekeeper
macOS's install-time guard - what triggers "Apple could not verify this app", and what developers must do to pass it cleanly.
Notarization
Apple's automated malware scan for Mac apps distributed outside the App Store - what it checks and why Gatekeeper demands it.
Microsoft Defender SmartScreen
Windows' download reputation system - why new installers get the blue "Windows protected your PC" wall, and how signing fixes it.
Snap Package
The Linux app format behind the Snap Store - what snaps are, where they run, and how they update.