Access Tokens

Visual Overview: sequenceDiagram participant App as Client Application participant AuthServer as Authorization Server participant Resource as Resource Server App->>AuthServer: 1. Client Credentials (client_id + secret) AuthServer->>AuthServer: 2. Validate Credentials AuthServer->>App: 3. Access Token App->>Resource: 4. API Request with Token Resource->>App: 5. Protected Resource Token revocation is a critical security feature in OAuth 2.0 that allows clients or authorization servers to invalidate access or refresh tokens before their natural expiration. This capability enhances control over user sessions and reduces risks in compromised environments. ...

I’ve seen teams waste weeks building custom auth when client credentials would’ve solved it in hours. OAuth 2.0’s Client Credentials Flow is for machine-to-machine (M2M) auth scenarios - when a service needs to access resources directly without any user involvement. This flow lets you secure server-to-server communication by allowing a client to authenticate itself and request an access token. Visual Overview: sequenceDiagram participant User participant App as Client App participant AuthServer as Authorization Server participant Resource as Resource Server User->>App: 1. Click Login App->>AuthServer: 2. Authorization Request AuthServer->>User: 3. Login Page User->>AuthServer: 4. Authenticate AuthServer->>App: 5. Authorization Code App->>AuthServer: 6. Exchange Code for Token AuthServer->>App: 7. Access Token + Refresh Token App->>Resource: 8. API Request with Token Resource->>App: 9. Protected Resource Why This Matters According to OWASP, improper authentication is consistently in the top 3 API security risks. Client credentials flow, when implemented correctly, eliminates the most common attack vectors in service-to-service communication. I’ve used this in 50+ enterprise deployments, and it’s the backbone of modern microservices architecture. ...