Xcode 10.1 was the final build fully tested and optimized for High Sierra. While Xcode 10.2.1 can technically launch on 10.13.6, it suffers from frequent crashes, broken Interface Builder rendering, and Swift 5 compilation issues. For professional work, stick to Xcode 10.1 .

The app will ask to install additional required components (like Command Line Tools and simulator runtimes). Allow it to proceed and enter your Mac’s administrator password when prompted. Once Xcode opens, you are good to start building projects! A Note on App Store Submission Restrictions

Once those components install, Xcode 10.1 is ready for development work.

You will need a free Apple Developer Account to download older versions of Xcode directly from Apple's servers.

Finding the correct version of Xcode for older macOS releases can be challenging. Apple strictly ties Xcode versions to specific macOS releases. If you are running macOS High Sierra 10.13.6, the standard Mac App Store will only offer the latest version of Xcode, which is incompatible with your operating system.

The primary obstacle facing a user on macOS High Sierra is the rigid compatibility matrix enforced by Apple. Unlike standard applications that might offer backward compatibility, Xcode is deeply integrated into the operating system’s kernel and frameworks. Consequently, a version of Xcode designed for the newest macOS often refuses to launch on an older OS. Conversely, using an older version of Xcode limits the developer’s ability to submit apps to the App Store, as Apple enforces strict rules on SDK usage. The High Sierra user is caught in a crossfire: the OS cannot be updated further, and the modern tools cannot be downgraded easily.

Xcode 10.1 supports iOS 12.1 by default. To test on older devices:

Open Terminal and run:

. Because the Mac App Store typically only offers the latest version of Xcode (which now requires much newer macOS versions), you must download the specific installer from Apple's developer archives. Apple Developer Steps to Download and Install Xcode 10.1

Some tools will still look for a newer Xcode. Force the system to use Xcode 10.1: