In this paper, we argue for the power of providing a common set of OS services to wide area applications, including mechanisms for resource discovery, a global namespace, remote process execution, resource management, authentication, and security. On a single machine, application developers can rely on the local operating system to provide these abstractions. In the wide area, however, application developers are forced to build these abstractions themselves or to do without. This ad-hoc approach wastes programmer effort and system resources. To address these problems, WebOS provides basic operating systems services needed to build applications that are geographically distributed, highly available, incrementally scalable, and dynamically reconfiguring. Experience with a number of applications developed under WebOS indicates that it simplifies system development and improves resource utilization. In particular, we use WebOS to implement Rent-A-Server to provide dynamic replication of overloaded services across the wide area in response to client demands.