Application bundle
| Filename extension | .app, .framework, .kext, .plugin, .docset, .xpc, .qlgenerator, .component, .saver, .mdimporter, etc |
|---|---|
| Uniform Type Identifier (UTI) | com.apple.application-bundle |
| UTI conformation | com.apple.application |
| Type of format | application software |
| Container for | executable binary, metadata, other bundles, any other file needed to run the application. |
| Extended from | directory bundle |
In NeXTSTEP, OPENSTEP, GNUstep, and their lineal descendants macOS and iOS, a bundle is a file directory with a defined structure and file extension, allowing related files to be grouped together as a conceptually single item.
Examples of bundles that contain executable code include applications, frameworks, and plugins. This kind of bundle usually contains one file representing executable code, and files that represent resources such as nibs, templates, images, sounds, and other media. On some other systems, such as Microsoft Windows, these resources are usually included directly in the executable file itself at compile time. On older Macintoshes, a similar technique is used, where additional metadata can be added to a file's resource fork. Similar in concept are the application directories used in RISC OS and on the ROX Desktop.
Examples of bundles that do not contain executable code include document packages (iWork documents) and media libraries (iPhoto Library).
Bundles are programmatically accessed with the NSBundle class in Cocoa, NeXTSTEP and GNUstep's Foundation frameworks, and with CFBundle in Core Foundation. The Uniform Type Identifier (UTI) for an Apple bundle is com.apple.bundle.
Application bundles are directory hierarchies, with the top-level directory having a name that ends with a .app extension. In an application bundle, the first directory in the bundle underneath the top-level directory is usually named Contents. Within Contents there is usually another directory (called MacOS on Macs, or using the application's name on GNUstep), which contains the application's executable code. Within the Contents folder there is usually also a directory called Resources, which contains the resources of the application.
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