Shibboleth is standards-based, open source middleware software which provides Web Single SignOn (SSO) across or within organizational boundaries. It allows sites to make informed authorization decisions for individual access of protected online resources in a privacy-preserving manner. The Shibboleth software implements the OASIS SAML v1.1 specification, providing a federated Single-SignOn and attribute exchange framework. Shibboleth also provides extended privacy functionality allowing the browser user and their home site to control the Attribute information being released to each Service Provider. Using Shibboleth-enabled access simplifies management of identity and access permissions for both Identity and Service Providers. Shibboleth is developed in an open and participatory environment, is freely available, and is released under the Apache Software License.