Security Assertion Markup Language (SAML) 2.0 is an XML-based open standard primarily used for web-based single sign-on (SSO) authentication across multiple websites and applications, enabling users to securely access various services with a single set of credentials. In the context of Kong Enterprise, the SAML implementation supports the service provider-initiated SSO flow, where a user trying to access a resource is redirected to an identity provider (IdP) for authentication if no active session exists. Once authenticated, the user is redirected back to the service provider with a SAML assertion, which is verified before granting access. The Kong SAML plugin, available in version 3.1 and above, facilitates this process with configuration options such as obtaining an IdP certificate, setting up an ACS endpoint, and using the IdP sign-in URL. Despite being considered legacy compared to newer protocols like OAuth 2.0 and OpenID Connect, SAML remains a widely adopted enterprise solution, prompting Kong to develop and expand its SAML plugin to support other identity providers in the future.