IPA File Format

IPA File Icon from iTunes 11

A IPA archive is the de facto way to package applications for iOS. The name has no official definition, but is commonly called iPhone Application by the iOS community. The file is just a renamed ZIP archive. Although any computer with a ZIP archive reader can extract an IPA, the images the file are typically saved as Apple PNG instead of the standardized PNG format. In addition, the application binary is encrypted with DRM which hinders the ability to examine the binary.

Structure

The basic structure of an IPA file is as follows;

• /iTunesArtwork
• /iTunesMetadata.plist
• /Payload/
  • ApplicationName.app/
    • ApplicationName
    • Various other application files

Use

Apple uses the IPA format for iOS applications in iTunes. Developers use the IPA format typically for Ad Hoc Distribution of apps to beta testers, IPAs can be created through Xcode. This requires an Apple Developer or Enterprise account if you want to distribute to non-jailbroken devices.

How to create

IPAs can be created either by hand or through Xcode's Product -> Archive (this requires an App Developer or Enterprise account) and can later be viewed through Organizer -> Archives. To create an IPA hand, build your application and locate the .app file for it. Create a root folder, inside this folder create another folder called 'Payload' and place your application in here. Next, create a 512x512 image for your icon, call it iTunesArtwork and place it in the root folder. Create an iTunesMetadata.plist file and place it in the root folder as well. ZIP the contents of the root folder and not the root folder itself, i.e. select the items inside the root folder and not the root folder itself. Use the following ZIP command to properly create IPA files;

zip -u -y -r -n .jpg:.JPG:.jpeg:.png:.PNG:.gif:.GIF:.Z:.gz:.zip:.zoo:.arc:.lzh:.rar:.arj:.mp3:.mp4:.m4a:.m4v:.ogg:.ogv:.avi:.flac:.aac IPAFileName.ipa ./*