JWT Authentication in ASP.NET Core 8 is one of the most important security features for modern Web APIs. In this step-by-step tutorial, you will learn how to implement JWT with refresh tokens using .NET 8.
“In this section, you will implement JWT authentication in ASP.NET Core 8 using token service.”
“To secure your API, enable JWT authentication with refresh token support in .NET 8.”
Authentication is one of the most essential features in modern APIs. ASP.NET Core 8 provides excellent support for JWT (JSON Web Token) authentication, making it easy to build secure APIs for web apps, mobile apps, and microservices.
In this step-by-step tutorial, you will learn:
- What JWT authentication is
- How to generate access tokens
- How to generate and store refresh tokens
- How to validate JWT tokens
- How to secure API endpoints
- How to refresh expired tokens
If you’re completely new to Web API development, you can also check our previous guide:
Build a REST API in ASP.NET Core 8 — Step-by-Step Tutorial
Let’s get started.
What is JWT Authentication? (Simple Explanation)
JWT stands for JSON Web Token, a compact and secure way to transmit user identity between client and server.
A JWT contains:
- Header → algorithm + token type
- Payload → user info (claims)
- Signature → verifies authenticity
JWT authentication uses two tokens:
Access Token (short lifespan)
Used for autorizations while accessing the API.
Expires in 1–15 minutes.
Refresh Token (long lifespan)
Used to generate a new access token when the old one expires.
Expires in days or weeks.
Step 1: Create a New ASP.NET Core 8 Web API Project
Open Visual Studio → Create New Project → ASP.NET Core Web API
Select:
.NET 8
Enable OpenAPI Support
Your project structure is ready.
Step 2: Install JWT Authentication Package
Run this command:
Step 3: Add JWT Settings in appsettings.json
Step 4: Create Models for Login & Tokens
Models/LoginModel.cs
Models/TokenResponse.cs
Step 5: Create Token Service
Services/ITokenService.cs
Services/TokenService.cs
Step 6: Configure Authentication in Program.cs
Add:
app.UseAuthentication();
app.UseAuthorization();
Step 7: Create Authentication Controller
Controllers/AuthController.cs
Step 8: Secure Any API Endpoint
Testing JWT Authentication
Use Swagger or Postman:
- Call
/api/auth/login→ Get access + refresh token - Use access token → Call
/api/secure-data - When access token expires → call
/api/auth/refresh
Frequently Asked Questions (FAQ)
1. What is JWT used for in ASP.NET Core?
JWT is used to authenticate and authorize API requests securely.
2. What is the difference between access token and refresh token?
Access token is short-lived, refresh token is long-lived and used to generate new access tokens.
3. Should I store refresh tokens in a database?
Yes, in production you should store them in a database, not in-memory.
4. Is JWT secure for authentication?
Yes, if implemented with HTTPS, strong secret key, and short token expiry.
5. Does ASP.NET Core 8 support JWT natively?
Yes, via Microsoft.AspNetCore.Authentication.JwtBearer.
- JWT Authentication in ASP.NET Core 8
- ASP.NET Core 8 JWT Tutorial
- JWT with refresh token in .NET 8
- .NET 8 authentication example
- ASP.NET Core secure API
- how to use JWT in ASP.NET Core
- setup JWT authentication in .NET 8
- refresh token implementation in Web API