Authorization

/ˌoʊ-pən-aɪ-di kəˈnɛkt/

n. “One login to rule them all… with modern flair.”

OpenID Connect is an authentication protocol built on top of the OAuth 2.0 framework. It allows clients—typically web and mobile applications—to verify the identity of a user based on the authentication performed by an identity provider (IdP) and to obtain basic profile information about that user in a secure and standardized way.

Unlike its predecessor, SAML, which is largely XML-based and enterprise-focused, OpenID Connect uses modern JSON-based tokens called ID Tokens, which are digitally signed JWTs (JSON Web Tokens). These tokens convey verified user information, such as username, email, and other attributes, enabling seamless Single Sign-On (SSO) across multiple services.

The typical OpenID Connect flow starts with the client redirecting the user to the identity provider for authentication. After the user authenticates, the IdP returns an ID Token and optionally an access token to the client. The ID Token proves the user’s identity, while the access token can authorize requests to protected APIs. This dual-token approach differentiates OpenID Connect from pure OAuth 2.0, which only handles authorization and leaves authentication ambiguous.

OpenID Connect has become the go-to protocol for modern applications because of its simplicity, security, and JSON-friendly design. It supports mobile, web, and API-based workflows, making it compatible with cloud services, social login providers, and enterprise identity systems. It integrates smoothly with OAuth 2.0 for delegated access while maintaining robust authentication guarantees.

Security is paramount. ID Tokens are signed and optionally encrypted, and HTTPS is required for all communications. Nonces, state parameters, and token validation rules prevent replay attacks, token substitution, and session hijacking. Developers must implement token verification correctly to avoid vulnerabilities—a misstep here can compromise the entire authentication flow.

In practice, OpenID Connect allows a user to log into a new web app using their Google, Microsoft, or other OpenID-enabled account. The client app doesn’t store credentials—it relies on the ID Token from the identity provider. This reduces password fatigue, centralizes security, and allows users to move across apps seamlessly.

Compared to SAML, OpenID Connect is lighter, JSON-native, and API-friendly, though SAML remains dominant in large enterprises. Together, these protocols provide a spectrum of options for modern and legacy Single Sign-On (SSO) implementations.

Today, OpenID Connect underpins millions of logins across cloud applications, consumer services, and mobile platforms. It’s not just an evolution of identity management—it’s a practical toolkit for making authentication seamless, secure, and developer-friendly in an era dominated by web and mobile apps.

/ˈoʊ-ˌɔːθ/

n. “Let someone borrow your keys without giving them the whole keyring.”

OAuth, short for Open Authorization, is a protocol that allows secure delegated access to resources without sharing credentials. Instead of giving a third-party app your username and password, OAuth enables the app to access certain parts of your account on your behalf via tokens that can be scoped and revoked.

Originally designed for web applications, OAuth has become ubiquitous in mobile apps, APIs, and cloud services. Services like Google, GitHub, and Twitter use it to let users authorize external apps while keeping their passwords private. When you “Sign in with Google,” you’re likely using OAuth.

At its core, OAuth separates authentication from authorization. Authentication is confirming identity, while authorization is granting specific access rights. With OAuth, users can grant a limited set of permissions — for example, allowing a photo printing app to access your gallery but not your contacts. The authorization server issues a token that the client uses to access the resource server, keeping your credentials safely stored.

A practical scenario: a productivity app wants to access your calendar. Using OAuth, the app redirects you to your calendar provider, you log in there, and consent to the permissions requested. The provider returns a short-lived access token to the app. The app can now read events without ever seeing your password. Tokens can expire or be revoked at any time, giving users granular control.

Security considerations are central to OAuth. Tokens must be securely stored and transmitted over HTTPS. Refresh tokens allow long-lived sessions without exposing credentials. Implementing OAuth incorrectly — such as using insecure redirect URIs or failing to validate tokens — can lead to account compromise.

OAuth has evolved through versions. OAuth 1.0 introduced signatures and complex cryptography, while OAuth 2.0 simplified flows and added support for modern web and mobile applications. Extensions like OpenID Connect layer authentication on top of OAuth for identity verification, making it a powerful framework for single sign-on (SSO).

Integration with APIs is also crucial. Many APIs require OAuth tokens to interact securely. This ensures that even if an application is compromised, the attacker cannot misuse the user’s credentials elsewhere. Tokens are scoped — limiting the actions that can be performed — which enhances security while maintaining usability.

In essence, OAuth allows safe, controlled, and revocable access delegation across systems. It balances convenience and security, enabling a connected ecosystem of apps and services without sacrificing the integrity of user credentials. When done right, it feels seamless; when done wrong, it can expose accounts, reminding developers that careful implementation is critical.