No authenticationScheme was specified 🟪 .NET

InvalidOperationException: No authenticationScheme was specified, and there was no DefaultChallengeScheme found

[Authorize] triggered a challenge, but no authentication handler/default scheme is configured.

Seen on: .NET

Meaning

AddAuthentication() was called without a default scheme, or not called at all, or UseAuthentication is missing. Specify a default scheme or set schemes on [Authorize].

Common causes

  • AddAuthentication() without default scheme
  • Authentication handler not registered (AddJwtBearer/AddCookie)
  • UseAuthentication/UseAuthorization order wrong

⚡ Quick fix

  1. Use AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
  2. Register the handler
  3. Call app.UseAuthentication() before app.UseAuthorization()

Detailed fix by platform

C#

  1. csharp
    builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme).AddJwtBearer();
app.UseAuthentication();
app.UseAuthorization();

How to diagnose

  1. Registration — Schemes configured?
  2. Middleware — Order

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