OAuth 2.0 is an authorization framework that allows applications to access user data from another service without sharing the user’s password.
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📌 Why Do We Use OAuth 2.0?
Avoid sharing user credentials
Secure third-party access
Used in social logins (Google, GitHub, etc.)
Works well with APIs and microservices
📌 Key Roles in OAuth 2.0
📌 How OAuth 2.0 Works
User tries to log in via third-party (e.g., Google)
User is redirected to Authorization Server
User grants permission
Authorization Server returns an Authorization Code
Client exchanges code for Access Token
Client uses token to access protected resources
🔹 Example Flow (Google Login)
Click “Login with Google”
Redirect to Google login page
User approves access
App receives access token
App fetches user profile data
📌 Important Concepts
🔑 Access Token
Used to access APIs
Short-lived
🔄 Refresh Token
Used to generate new access tokens
Long-lived
📌 OAuth 2.0 Grant Types
🚀 Advantages
✔️ Secure (no password sharing)
✔️ Scalable for modern apps
✔️ Widely adopted standard
✔️ Works with APIs & mobile apps
⚠️ Disadvantages
❌ Complex to implement
❌ Requires proper token management
❌ Misconfiguration can lead to vulnerabilities
🎯 OAuth 2.0 vs JWT
OAuth 2.0 → Authorization framework
JWT → Token format used inside OAuth
👉 They are often used together in real-world applications.
⚡ Real-Time Use Cases
Social login (Google, Facebook, GitHub)
API authorization
Microservices security
Single Sign-On (SSO)
🔥 OAuth 2.0 in Java
In Java (Spring Boot), OAuth 2.0 is implemented using:
Spring Security OAuth
Keycloak / Auth0 integration
✅ Conclusion
OAuth 2.0 is a powerful and secure way to allow third-party access to user data without exposing credentials. It is widely used in modern applications and is a must-know concept for backend developers.
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