We distribute our iPhone and iPad applications in an .zip or .ipa file to our clients for testing in an ad-hoc group. There is no need to speak about .zip file. The .ipa filename extension is assigned by Apple for applications that are downloaded from iTunes App Store. While we are developing your application, we usually email one of these files directly to you without interacting with App Store. We attach a second file – a .mobileprovision profile – to be able to join the ad-hoc group. This second file that contains your device UDID is needed to allow the application to run on your iPhone. Once you have got these two files from us, you will need to open iTunes and have your device ready and connected to your computer: 1. Save the .mobileprovision and .zip (or .ipa) files to your computer’s local drive or desktop if they are not already there. Unzip the .zip file that contains a folder. You will need the xxxx.app file that is inside that folder. 2. Open the iTunes. Connect your iPhone or iPad. 3. Drag and drop the .mobileprovision file into iTunes in the upper left corner, under the Library section at the Application group. If you receive an error message, we likely sent you a wrong provisioning profile, so let us know it. 4. Drag and drop the .app (or .ipa) file to the Application folder. In iTunes verify that the program is listed as an application. By opening the Library -> Application folder find the name of our application and a universal (A) icon above it. 5. Synchronize the Application folder with your device and keep it synchronized 6. Try to run our iPhone program on your device The iTunes library is an index list that iTunes uses to organize your music and other media like our iPhone applications. When the file we send you is an ourprogram.ipa file, the actual app is inside the compressed .ipa file, but you do not have to unzip it. If you delete that .ipa file, it won’t be in your library any longer and it will be removed from your iPhone/iPad the next time you synchronize, so do not delete it during ad-hoc testing. There is no such side-effect with the ZIP file as you have already extracted the ourprogram.app file and you have added it to the Application folder. You may now delete the ZIP file. Detailed instructions on unpacking Windows 7 ZIP file can be read from here. Typical errors in iPhone and iPad projects: Error messages during ad hoc distribution. Happy testing!