auth0-aspnetcore-api
Use when protecting ASP.NET Core Web API endpoints with JWT Bearer token validation, scope checks, or DPoP binding. Integrates Auth0.AspNetCore.Authentication.Api for stateless REST APIs receiving access tokens from frontends or mobile apps.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/auth0/agent-skills --skill auth0-aspnetcore-api- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads auth0-aspnetcore-api automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
Auth0 ASP.NET Core Web API Integration
Protect ASP.NET Core Web API endpoints with JWT access token validation using Auth0.AspNetCore.Authentication.Api.
Prerequisites
- .NET 8.0 SDK or higher
- Auth0 API configured (not Application - must be API resource)
- If you don't have Auth0 set up yet, use the
auth0-quickstartskill first
When NOT to Use
- Server-rendered web applications - Use session-based auth (Auth0.AspNetCore.Authentication) for MVC/Razor Pages apps
- Single Page Applications - Use
auth0-react,auth0-vue, orauth0-angularfor client-side auth - Mobile applications - Use
auth0-react-nativefor React Native/Expo - Blazor WebAssembly - Requires different auth approach (OIDC client-side)
Quick Start Workflow
1. Install SDK
dotnet add package Auth0.AspNetCore.Authentication.Api
2. Create Auth0 API
You need an API (not Application) in Auth0.
STOP — ask the user before proceeding.
Ask exactly this question and wait for their answer before doing anything else:
"How would you like to create the Auth0 API resource?
- Automated — I'll run Auth0 CLI scripts that create the resource and write the exact values to your appsettings.json automatically.
- Manual — You create the API yourself in the Auth0 Dashboard (or via
auth0 apis create) and provide me the Domain and Audience.Which do you prefer? (1 = Automated / 2 = Manual)"
Do NOT proceed to any setup steps until the user has answered. Do NOT default to manual.
If the user chose Automated, follow the Setup Guide for complete CLI scripts. The automated path writes appsettings.json for you — skip Step 3 below and proceed directly to Step 4.
If the user chose Manual, follow the Setup Guide (Manual Setup section) for full instructions including User Secrets and environment variable options. Then continue with Step 3 below.
Quick reference for manual API creation:
# Using Auth0 CLI
auth0 apis create \
--name "My ASP.NET Core API" \
--identifier https://my-api.example.com
Or create manually in Auth0 Dashboard → Applications → APIs
3. Configure appsettings.json
{
"Auth0": {
"Domain": "your-tenant.auth0.com",
"Audience": "https://my-api.example.com"
}
}
Important: Domain must NOT include https://. The library constructs the authority URL automatically.
4. Configure Program.cs
var builder = WebApplication.CreateBuilder(args);
// Register Auth0 JWT validation
builder.Services.AddAuth0ApiAuthentication(options =>
{
options.Domain = builder.Configuration["Auth0:Domain"];
options.JwtBearerOptions = new JwtBearerOptions
{
Audience = builder.Configuration["Auth0:Audience"]
};
});
builder.Services.AddAuthorization();
var app = builder.Build();
// Middleware order matters: authentication before authorization
app.UseAuthentication();
app.UseAuthorization();
// Add your endpoints here (see Step 5)
app.MapGet("/api/public", () => Results.Ok(new { message = "Public" }));
app.Run();
5. Protect Endpoints
Minimal API:
// Public endpoint - no authentication
app.MapGet("/api/public", () => Results.Ok(new { message = "Hello from a public endpoint!" }));
// Protected endpoint - requires valid JWT
app.MapGet("/api/private", (HttpContext ctx) =>
{
var userId = ctx.User.FindFirst("sub")?.Value;
return Results.Ok(new { message = "Hello from a protected endpoint!", userId });
}).RequireAuthorization();
Controller-based:
[ApiController]
[Route("api")]
public class MessagesController : ControllerBase
{
[HttpGet("public")]
public IActionResult Public() =>
Ok(new { message = "Hello from a public endpoint!" });
[Authorize]
[HttpGet("private")]
public IActionResult Private() =>
Ok(new { message = "Hello from a protected endpoint!", userId = User.FindFirst("sub")?.Value });
}
6. Test API
Test public endpoint:
curl http://localhost:5000/api/public
Test protected endpoint (requires access token):
curl http://localhost:5000/api/private \
-H "Authorization: Bearer YOUR_ACCESS_TOKEN"
Get a test token via Client Credentials flow or Auth0 Dashboard → APIs → Test tab.
Common Mistakes
| Mistake | Fix |
|---|---|
Domain includes https:// | Use your-tenant.auth0.com format only - no scheme prefix |
| Audience doesn't match API Identifier | Must exactly match the API Identifier set in Auth0 Dashboard |
| Created Application instead of API in Auth0 | Must create API resource in Auth0 Dashboard → Applications → APIs |
| Wrong middleware order | UseAuthentication() must come before UseAuthorization() |
| Using ID token instead of access token | Must use access token for API auth, not ID token |
| HTTPS certificate errors locally | Run dotnet dev-certs https --trust |
Scope-Based Authorization
See Integration Guide for defining and enforcing scope policies.
DPoP Support
Built-in proof-of-possession token binding per RFC 9449. See Integration Guide for configuration.
Related Skills
auth0-quickstart- Basic Auth0 setupauth0-mfa- Add Multi-Factor Authenticationauth0-cli- Manage Auth0 resources from the terminal
Quick Reference
Configuration Options:
options.Domain- Auth0 tenant domain, nohttps://prefix (required)options.JwtBearerOptions.Audience- API Identifier from Auth0 API settings (required)options.JwtBearerOptions- Full access to underlying Microsoft JWT Bearer options
User Claims:
ctx.User.FindFirst("sub")?.Value- User ID (subject)ctx.User.FindFirst("scope")?.Value- Space-separated scopesctx.User.FindAll("scope")- All scope claims
Common Use Cases:
- Protect Minimal API routes →
.RequireAuthorization()(see Step 5) - Protect controller actions →
[Authorize]attribute (see Step 5) - Scope enforcement → Integration Guide
- DPoP token binding → Integration Guide
- Advanced JWT Bearer config → API Reference
Detailed Documentation
- Setup Guide - Auth0 CLI setup, environment configuration
- Integration Guide - Scope policies, DPoP, controller patterns, error handling
- API Reference - Complete configuration options and extension methods
References
FAQ
What does the auth0-aspnetcore-api skill do?
Use when protecting ASP.NET Core Web API endpoints with JWT Bearer token validation, scope checks, or DPoP binding. Integrates Auth0.AspNetCore.Authentication.Api for stateless REST APIs receiving access tokens from frontends or mobile apps.
How do I install auth0-aspnetcore-api?
Run npx skills add https://github.com/auth0/agent-skills --skill auth0-aspnetcore-api in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/auth0-aspnetcore-api/ (personal) or .claude/skills/auth0-aspnetcore-api/ (project).
Which AI agents can use auth0-aspnetcore-api?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is auth0-aspnetcore-api safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains auth0-aspnetcore-api?
It is published by auth0 in auth0/agent-skills, and it is an official skill from the maker of the technology it covers. It has 490 recorded installs.
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