Web services are software systems designed to support interoperable machine-to-machine interaction over a network. They are a type of internet software that use standardized messaging protocols and are made available from an application service providers web server for use by a client or other web-based applications. Web services are built using open standards and protocols in order to integrate with various applications. They allow different organizations or applications from multiple sources to communicate without the need to share sensitive data or IT infrastructure.

Web services use XML-based information exchange systems that use the internet for direct application-to-application interaction. XML is used to encode all communications to a web service. For example, a client invokes a web service by sending an XML message, then waits for a corresponding XML response. As all communication is in XML, web services are not tied to any one operating system or programming language.

Web services have an interface described in a machine-processable format, specifically WSDL. Other systems interact with the web service in a manner prescribed by its description using SOAP-messages, typically conveyed using HTTP with an XML serialization in conjunction with other web-related standards.

Web services are used for a variety of applications, but the most common is for reusing code and connecting existing programs. The web service method can help developers segment applications into components that can be used and reused for various needs.