Refresh Tokens & Secure Session Management in ASP.NET Core

Authentication doesn’t end after issuing a JWT. Real-world applications must handle token expiration, session continuity, and security threats like token theft.
In this article, we’ll explore Refresh Tokens and how to build secure session management in ASP.NET Core.

Why Refresh Tokens Are Important

JWT access tokens are:

• Stateless

• Short-lived

• Not revocable easily

If access tokens never expire → huge security risk
If they expire too quickly → bad user experience

👉 Refresh tokens solve this problem

Token Strategy (Best Practice)

| Token Type    | Lifetime     | Purpose              |
| ------------- | ------------ | -------------------- |
| Access Token  | 5–15 minutes | API authorization    |
| Refresh Token | Days / Weeks | Get new access token |

How Refresh Tokens Work (Flow)

1. User logs in

2. Server issues:

   • Access Token (JWT)

   • Refresh Token (secure random string)

3. Client stores:

   • Access Token → memory

   • Refresh Token → HTTP-only cookie

4. Access token expires

5. Client calls /refresh

6. Server validates refresh token

7. New access token is issued

Designing a Secure Refresh Token System

🔐 Key Security Principles

• Refresh tokens must be:

  • Random

  • Stored server-side

  • Revocable

• Use