Double-click the downloaded Xcode_10.1.xip file in your folder.

If you attempt to install Xcode 10.2 or higher, you'll see an error message like: "You can't use this version of the application 'Xcode' with this version macOS. You have macOS 10.13.6. The application requires macOS 10.14.3 or later".

:

Error: "Xcode cannot be opened because it is from an unidentified developer"

Check if your Mac is compatible with these newer operating systems before proceeding.

If you are interested, I can also provide a guide on how to update your Mac to a newer OS if you find these limitations too restrictive.

Once expanded, you will see the Xcode icon (the hammer and blueprint).

Once extraction finishes, you will see an application icon in your folder.

xcode-select --install

Notes/assumptions: you want a version of Xcode that runs on macOS High Sierra 10.13.6 (released 2017). The latest Xcode does not support High Sierra; use Xcode 10.1 or Xcode 9.4.x (Xcode 10.1 is the last that officially supports 10.13.6).

Locate (released in late 2018) and click the link to download the Xcode_10.1.xip file.

To get started, you'll need to have at least 13GB of free disk space for the Xcode 10.1 .xip file and its subsequent installation.

Finding a compatible version of Xcode for older macOS versions can be challenging. Apple limits the Mac App Store to the newest Xcode releases, which do not support legacy operating systems. However, you can still download, install, and run a fully functional version of Xcode on macOS High Sierra 10.13.6 by using Apple's official developer archives.

Therefore, your primary goal will be to acquire and install either Xcode 9.4.1 or Xcode 10.1.

If your goal is to learn programming basics, maintain an older project, or run software that requires Xcode, this guide is perfect. However, if you need to develop and distribute modern apps for the App Store, you will need to consider upgrading your Mac to a model that supports a newer version of macOS, such as Mojave (10.14), Catalina (10.15), or later.

Sign in with your standard Apple ID and follow the on-screen prompts to accept the developer agreement and activate a free account. Step 3: Download Xcode 10.1