how to Implement JWT authentication in an ASP.NET Core application

May 31 2025 by Admin

In this article, we have described how to Implement JWT (JSON Web Token) authentication in an ASP.NET Core application.

In this article, we have described how to Implement JWT (JSON Web Token) authentication in an ASP.NET Core application. You can see the example code below.

1.Install Required Packages

In your project’s .csproj or via terminal

dotnet add package Microsoft.AspNetCore.Authentication.JwtBearer

2. Configure JWT in appsettings.json

"JwtSettings": {

"SecretKey": "YourVeryStrongSecretKeyHere", // Must be 16+ characters

"Issuer": "YourApp",

"Audience": "YourAppUsers",

"ExpiryInMinutes": 60

}

3. Create JWT Settings Class

{

public string SecretKey { get; set; }

public string Issuer { get; set; }

public string Audience { get; set; }

public int ExpiryInMinutes { get; set; }

}

4. Register Authentication Services in Program.cs

var builder = WebApplication.CreateBuilder(args);

// Bind JWT settings

var jwtSettingsSection = builder.Configuration.GetSection("JwtSettings");

builder.Services.Configure<JwtSettings>(jwtSettingsSection);

var jwtSettings = jwtSettingsSection.Get<JwtSettings>();

var key = Encoding.ASCII.GetBytes(jwtSettings.SecretKey);

// Add JWT authentication

builder.Services.AddAuthentication(options =>

{

options.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;

options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;

})

.AddJwtBearer(options =>

{

options.TokenValidationParameters = new TokenValidationParameters

{

ValidateIssuer = true,

ValidateAudience = true,

ValidateLifetime = true,

ValidateIssuerSigningKey = true,

ValidIssuer = jwtSettings.Issuer,

ValidAudience = jwtSettings.Audience,

IssuerSigningKey = new SymmetricSecurityKey(key)

};

});

builder.Services.AddAuthorization();

var app = builder.Build();

// Use Authentication and Authorization

app.UseAuthentication();

app.UseAuthorization();

app.MapControllers();

app.Run();

5. Create Token Generation Method.

public class TokenService

{

private readonly JwtSettings _jwtSettings;

public TokenService(IOptions<JwtSettings> jwtSettings)

{

_jwtSettings = jwtSettings.Value;

}

public string GenerateToken(string username)

{

var tokenHandler = new JwtSecurityTokenHandler();

var key = Encoding.ASCII.GetBytes(_jwtSettings.SecretKey);

var tokenDescriptor = new SecurityTokenDescriptor

{

Subject = new ClaimsIdentity(new[]

{

new Claim(ClaimTypes.Name, username)

}),

Expires = DateTime.UtcNow.AddMinutes(_jwtSettings.ExpiryInMinutes),

Issuer = _jwtSettings.Issuer,

Audience = _jwtSettings.Audience,

SigningCredentials = new SigningCredentials(new SymmetricSecurityKey(key), SecurityAlgorithms.HmacSha256Signature)

};

var token = tokenHandler.CreateToken(tokenDescriptor);

return tokenHandler.WriteToken(token);

}

6. Create Login Endpoint in Controller.

[ApiController]

[Route("api/[controller]")]

public class AuthController : ControllerBase

{

private readonly TokenService _tokenService;

public AuthController(TokenService tokenService)

{

_tokenService = tokenService;

}

[HttpPost("login")]

public IActionResult Login([FromBody] LoginModel model)

{

// Validate user here (e.g. against a database)

if (model.Username == "admin" && model.Password == "password")

{

var token = _tokenService.GenerateToken(model.Username);

return Ok(new { Token = token });

}

return Unauthorized();

}

public class LoginModel

{

public string Username { get; set; }

public string Password { get; set; }

}

7. Protect Your API Endpoints. using Authorize Keyword

[Authorize]

[HttpGet("secure-data")]

public IActionResult GetSecureData()

{

var username = User.Identity?.Name;

return Ok($"Hello {username}, this is protected data.");

}

ASP.NET CORE
JWT Token

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how to Implement JWT authentication in an ASP.NET Core application

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Home > ASP.NET > how to Implement JWT authentication in an ASP.NET Core application

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