The last decade has seen a tremendous growth in the usage of the World Wide Web. The Web has grown so fast that it seems to be becoming an unusable and slow behemoth. Web caching is one way to tame and make this behemoth a friendly and useful giant. The key idea in Web caching is to cache frequently accessed content so that it may be used profitably later. This book focuses entirely on Web caching techniques. Much of the material in this book is very relevant for those interested in understanding the wide gamut of Web caching research. It will be helpful for those interested in making use of the power of the Web in a more profitable way. Audience and purpose of this book This book presents key concepts in Web caching and is meant to be suited for a wide variety of readers including advanced undergraduate and graduate students' programmers' network administrators' researchers' teachers' techn- ogists and Internet Service Providers (ISPs).