OpenID Connect (OIDC) is an identity layer on top of OAuth 2.0. If you’ve used “Sign in with Google/Microsoft/Okta/Auth0”, you’ve already used OIDC. In modern single-page apps (SPAs), the best practice is: Authorization Code Flow + PKCE Store tokens in memory (avoid localStorage when possible) Use the provider’s well-known discovery document Protect routes and attach access tokens to API calls This guide shows an end-to-end setup for both Angular and React .