New Tools for 64-bit Support in Xcode 9.3 Beta
The last macOS release to support 32-bit apps without compromise is macOS High Sierra. Make sure future releases of your app are 64-bit compatible by using new diagnostic tools in Xcode 9.3 beta and testing on macOS 10.13.4 beta. This version of Xcode also builds 64-bit apps by default.
Download Xcode 9.3 beta