On today's web, performance isn't just a nice-to-have-it's essential. A slow or unstable experience drives users away, while a fast, reliable one builds trust and keeps them engaged. Web Performance Engineering in the Age of AI is a comprehensive, hands-on guide for developers, technical leads, and performance engineers focused on delivering high-impact, user-first web experiences. Written by Addy Osmani, director at Google Cloud AI, this book combines deep technical insight with a strong emphasis on usability and real-world effectiveness. Through case studies, modern optimization techniques, and a user-centered approach, you'll learn how to identify bottlenecks, debug performance issues, and apply improvements that make a measurable difference. Grounded in current browser internals and performance metrics, this book prepares you to design and maintain faster, more resilient websites at scale. Understand how users perceive speed-and why it mattersEvaluate and improve performance using key metricsOptimize for stability, responsiveness, and load timeIdentify and address the most common performance bottlenecksApply real-world strategies that lead to lasting results