Tracking developer onboarding metrics is crucial to understand how quickly new developers join a team and become productive. Key metrics include Time to First Commit, Time to Technical Autonomy, Development Environment Setup Time, Onboarding Documentation Completeness Score, Pull Request/Code Review Success Rate for New Developers, and Onboarding Completion Rate. These metrics help identify areas of improvement in the onboarding process, such as streamlining setup times, providing comprehensive documentation, and establishing effective mentoring programs. By tracking these metrics consistently, organizations can optimize their onboarding processes, improve developer productivity, and enhance overall engineering success.