After you upgrade to xCode 6.4 you will notice that the SDK for iOS 7.1 is no longer available. If you still want to be able to build for iOS7 and run a simulator for iOS7 then you will need to do a little bit of manual work. First if you go to Preferences --> Downloads within xCode you should see a component listed for the iOS 7.1 simulator. Click on the download arrow in order for it to be downloaded and installed. However you will notice that there is no download for the base SDK for 7.1. You will need to manually install it in order for it to be available to xCode 6.4. You will want to check and confirm what SDKs are actually installed. You can check by opening a terminal on your MAC and then proceeding to the directory /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs . If you do not see a folder for iPhoneOS7.1.sdk you will want to extract a copy of the SDK into your Xcode SDK directory structure. You could either attempt to cop