自研JWT签发与IdentityServer4(OIDC)对比：Web API是否需用OIDC？

Hey there! Since you're already successfully rolling with custom JWT issuance and AddJwtBearer validation in your Web API, let's break down why you might consider moving to OpenID Connect (OIDC) with IdentityServer4, and how to decide if it's right for your use case.

Key Advantages of OIDC (with IdentityServer4) Over Custom JWTs #

• Standardized Identity Layer
  OIDC builds on OAuth2 to define a universal identity protocol—no more reinventing the wheel for authentication flows, token formats, or identity claims. It specifies standard claims (like sub for user ID, name, email) and standardized endpoints (authorization, token, user info) that any compliant client can integrate with. If you ever need to add a new app (SPA, mobile, etc.) or let third parties access your API, they won't have to learn your custom JWT structure—they can use off-the-shelf OIDC libraries.

• Centralized Identity Management
  IdentityServer4 acts as a single source of truth for authentication. If you have multiple apps (Web API, frontend SPA, mobile app), users only need to log in once (Single Sign-On, SSO) to access all of them. You also get centralized control over user credentials, roles, and permissions—no more duplicating user data or auth logic across every service.

• Built-In Security Best Practices
  IdentityServer4 handles all the tricky security details you might miss with custom JWTs:

  • Asymmetric signing (e.g., RS256) by default—your API only needs a public key to validate tokens, so the private signing key stays safe in IdentityServer (no more sharing symmetric keys across services).
  • Out-of-the-box support for secure flows like Authorization Code with PKCE (critical for SPAs and mobile apps to prevent authorization code interception).
  • Token revocation, introspection (check if a token is still valid even before it expires, e.g., if a user is disabled), and anti-CSRF protections.

• Support for All Client Types
  Whether you're building a traditional server-side web app, a single-page app, a mobile app, or even IoT devices, IdentityServer4 has pre-built support for the appropriate OIDC flows. Custom JWT setups often struggle to adapt to different client security requirements—you'd have to manually implement things like PKCE or refresh token rotation, which is error-prone.

• Extensible Identity Integration
  IdentityServer4 plays nicely with existing user stores: ASP.NET Core Identity, Active Directory, custom databases, or even social login providers (Google, Facebook, etc.). Adding multi-factor authentication (MFA) or custom user claims is straightforward, whereas with custom JWTs you'd have to build all that logic from scratch.

How to Decide If You Need OIDC #

Stick with your current custom JWT setup if:

• You only have one Web API with no plans to add other clients (frontend apps, mobile, etc.).
• You don't need to support third-party integrations (no external apps accessing your API).
• Your authentication logic is extremely simple (e.g., basic user/password checks with no roles, MFA, or SSO requirements).

You should consider moving to OIDC with IdentityServer4 if:

• You're adding multiple clients (SPA, mobile, other APIs) that need to share user identity.
• You want to enable third-party developers to access your API securely (OIDC is the industry standard for this).
• You need robust security features like MFA, token revocation, or SSO/Single Log-Out (SLO).
• You want to centralize user management instead of duplicating auth logic across services.

内容的提问来源于stack exchange，提问作者Konrad