OAuth

An open standard for access delegation, commonly used as a way for Internet users to grant websites or applications access to their information on other websites but without giving them the passwords.

OAuth (Open Authorization) is an open standard protocol for token-based authorization on the internet. It allows users to grant third-party applications limited access to their resources on another service without sharing their credentials. OAuth 2.0 is the current version and is widely adopted across the industry.

OAuth 2.0 defines several authorization flows (called grant types) for different scenarios: Authorization Code for server-side applications, Implicit for browser-based apps (now deprecated in favor of PKCE), Client Credentials for machine-to-machine communication, and Device Code for devices with limited input capabilities. Each flow results in the issuance of an access token that the client uses to authenticate API requests.

API gateways commonly validate OAuth tokens as part of their authentication pipeline. The gateway can verify token signatures, check expiration, validate scopes, and reject unauthorized requests before they reach backend services. This centralizes token validation logic and ensures consistent security enforcement across all API endpoints. Integration with OAuth providers like Auth0, Okta, or Supabase is a common API gateway feature.