What is APP?

APP bundles are macOS application packages - directories that appear as single files in Finder but contain all components needed to run an application. Structure includes: executable binary (Mach-O format), Info.plist metadata file, icon resources, localized strings, frameworks, and support files. Users can right-click and "Show Package Contents" to explore the bundle. APP bundles enable drag-and-drop installation - just copy to Applications folder.

APP is the universal format for all macOS software - from Safari and Mail (built-in) to third-party apps like Chrome, Slack, and Photoshop. Downloaded from Mac App Store or developer websites as .dmg disk images containing .app bundles. Code signing and notarization ensure security. Universal apps contain binaries for both Intel and Apple Silicon. APP bundles can include embedded frameworks, plugins, and helper tools, making them self-contained and portable.

Did you know? .app files are actually folders disguised as single files by macOS!

History

Apple introduced the application bundle concept with the original Macintosh, refining it through NeXTSTEP and finally establishing the modern .app format with Mac OS X.

Key Milestones

  • 1984: Original Mac application bundles
  • 1989: NeXTSTEP .app bundles
  • 2001: Mac OS X .app standardization
  • 2011: Mac App Store launch
  • 2020: Universal apps (Intel + ARM)
  • Present: Apple Silicon transition

Key Features

Core Capabilities

  • Self-Contained: All resources bundled
  • Drag-to-Install: No installer needed
  • Universal Binaries: Intel + Apple Silicon
  • Code Signing: Security verification
  • Localization: Multi-language support
  • Sandboxing: Security isolation

Common Use Cases

Desktop Apps

All macOS applications

Developer Tools

Xcode, VS Code, etc.

Games

macOS gaming

Creative Apps

Adobe, Final Cut Pro

Advantages

  • Simple drag-and-drop installation
  • Self-contained (all resources included)
  • No registry or system pollution
  • Easy to uninstall (delete .app)
  • Universal binary support
  • Strong security with code signing
  • Clean, organized structure

Disadvantages

  • macOS-only (not cross-platform)
  • Can be large (duplicated frameworks)
  • Code signing requirements strict
  • Notarization needed for distribution
  • Complex bundle structure for developers
  • Universal binaries increase size

Technical Information

Format Specifications

Specification Details
File Extension .app
Type Directory bundle (appears as file)
Executable Mach-O binary format
Structure Contents/ directory with MacOS/, Resources/
Metadata Info.plist (XML property list)
Architecture x86_64, arm64, or Universal

Common Tools

  • Development: Xcode, Swift Package Manager
  • Distribution: Mac App Store, notarization tools
  • Inspection: otool, codesign, lipo (check architecture)
  • Creation: Xcode build system, Automator