The importance of web crawling/web harvesting services in librarianship cannot be over emphasized especially now that libraries around the globe have been mandated to switch to electronic methods so as to satisfy their users effectively. This paper discusses the potential benefits libraries will derive by promoting the use of web crawling technologies for their library services with reference to Nigeria. It further explores the concept and significance of web crawling, web crawlers, approaches to web crawling, and web crawling in libraries. The paper also highlights the experiences of other libraries globally on the integration of crawling technologies in their digital information services. It also justifies the need for librarians in Nigeria to adopt web crawling technologies in their libraries. Challenges that could undermine the successful application of such technologies were equally explored. The paper concludes that, if appropriately used, the content of the chapter will provide valuable additional input to information professionals for the design of the web archiving as a tool for preserving information resources deposited in multiple websites so as to ensure its security by storing it on their local library databases for future use.