How Single Sign-On (SSO) works – and how to add it to your app

Single Sign-On (SSO) is an authentication method that allows users to log in once and gain access to multiple applications or services without having to authenticate again for each one. Instead of managing separate usernames and passwords for every tool—from internal dashboards to third-party SaaS apps—users authenticate through a single identity provider (IdP) like Okta, Azure AD, or Google Workspace.

This centralized approach to login helps organizations streamline access control, enhance security, and reduce friction for end-users. It also makes life easier for IT teams, who can enforce security policies and manage user access from one place.

For developers building modern web apps—especially those targeting enterprise customers—supporting SSO is often not just a nice-to-have, but a hard requirement.

In this guide, we’ll explore how SSO works under the hood, the protocols involved (SAML and OIDC), how to integrate it using WorkOS, and what security best practices to follow.

!!TL;DR: SSO enables users to log in once and access multiple applications via a trusted identity provider. SAML and OIDC are the two most common protocols used. With WorkOS, you can integrate both quickly using a single API.!!

What is Single Sign-On (SSO)?

Single Sign-On (SSO) is a secure authentication method that allows users to access multiple applications with just one set of login credentials. Instead of remembering a username and password for every tool they use—like Slack, Salesforce, or internal dashboards—users log in once via an identity provider (IdP), and that authentication is trusted by other services.

For organizations, SSO significantly improves security posture and user experience. It centralizes identity management, reduces helpdesk tickets related to forgotten passwords, and makes it easier to control access when employees join or leave. For developers building B2B SaaS apps, integrating SSO is often a prerequisite for landing enterprise customers.

Why companies use SSO

SSO solves real problems for both IT administrators and end-users:

• Reduced password fatigue: With dozens of apps in the average workplace, users no longer have to manage separate credentials.
• Centralized security policies: IT teams can enforce things like 2FA, IP restrictions, and session lifetimes via the IdP.
• Faster onboarding and offboarding: Provisioning or deactivating users in one place (the IdP) instantly affects access across all apps.
• Compliance alignment: SSO helps meet standards like SOC 2, HIPAA, and ISO 27001 by offering auditable, centralized control.

From a product perspective, SSO is increasingly table stakes. Enterprise procurement teams often require SSO (and provisioning via SCIM) before signing a deal.

The core concept: Trust delegation

At the heart of SSO is the idea of delegating trust from one service (a service provider, or SP) to another system (an identity provider, or IdP). Instead of authenticating users themselves, applications redirect users to an IdP they trust—such as Okta, Azure AD, Google Workspace, or Ping Identity.

When the IdP authenticates the user, it sends a cryptographically signed SAML assertion (in SAML) or ID token (in OIDC) back to the application. That assertion or token includes information like the user's email, name, and unique identifier. If the signature checks out, the app trusts the identity claim and logs the user in.

This decouples authentication from application logic, which is more secure and scalable across many services.

The SSO authentication flow (step-by-step)

Here’s how a typical SAML-based SSO login works:

1. User visits your app (the service provider): For example, app.company.com/dashboard. The app sees the user is not logged in and initiates SSO.
2. App redirects the user to the IdP: It constructs a SAML authentication request and sends it to an IdP such as Okta. WorkOS helps abstract this step for developers.
3. User logs in at the IdP: The user enters credentials (e.g., their company email and password). The IdP authenticates them—optionally using 2FA or biometric auth.
4. IdP returns a SAML assertion: Once authenticated, the IdP sends a signed SAML response back to the app (typically via a browser POST).
5. The app validates the token and grants access: If the assertion is valid, the app logs the user in, optionally creating a new user record using JIT (just-in-time) provisioning.

Using OIDC, the process is nearly identical, but the format differs (JSON tokens over REST instead of XML via POST). WorkOS supports both.

SAML vs. OIDC: What’s the difference?

The two most common protocols used to implement Single Sign-On are SAML (Security Assertion Markup Language) and OIDC (OpenID Connect). While both serve the same purpose—enabling delegated authentication—they differ in how they work under the hood.

• SAML uses XML-formatted assertions and typically relies on browser redirects with form POSTs, making it common in legacy enterprise systems.
• OIDC, built on OAuth 2.0, uses JSON Web Tokens (JWTs) and REST-based flows, making it a better fit for modern web and mobile applications.

Here’s how they compare:

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WorkOS abstracts away these protocol differences. Developers integrate once with the WorkOS API, and enterprise customers can use whichever protocol their IdP supports.

Real-world example: Google Workspace + your app (via WorkOS)

Let’s say your B2B SaaS app integrates with WorkOS and an enterprise customer uses Google Workspace as their IdP:

1. The app redirects the user to Google when SSO is triggered.
2. The user authenticates with Google (email, password, 2FA).
3. Google returns a signed token or SAML assertion to the app via WorkOS.
4. WorkOS verifies the token/assertion and maps it to a user in your app.
5. The user lands in your dashboard, logged in and authenticated.

With WorkOS, you don’t need to implement the logic for SAML or OIDC yourself—just a few API calls and config settings.

How to add SSO to your app with WorkOS

Implementing enterprise-grade Single Sign-On in your app with WorkOS takes just a few steps:

1. Create a WorkOS account.
2. Integrate the WorkOS SDK or API into your app. You'll use endpoints to initiate SSO flows and handle authentication callbacks.
3. Configure your redirect URI (your app’s endpoint to which WorkOS will redirect after a user has authenticated).
4. Build your own authentication UI or use AuthKit, a fully customizable plug-and-play login box powered by Radix, the most popular open-source design system.
5. Connect an identity provider (IdP) in the WorkOS dashboard—either manually or by inviting your customer to self-configure. Find detailed steps on how to configure each IdP in our Integrations page.
6. Handle the user session using the authenticated profile returned by WorkOS.

That’s it. Whether your customer uses Okta, Azure AD, Google Workspace, or something else—WorkOS handles the protocol details so you don’t have to.

Start authenticating in minutes with our quickstart guides:

• Authenticate users with AuthKit
• Add SSO to your app using your own login box

Or follow a step-by-step tutorial tailored to your language and IdP:

• SAML SSO with WorkOS, Okta, and Node
• SAML SSO with WorkOS, Entra ID, and Node
• SAML SSO with WorkOS, Okta, and Go
• SAML SSO with WorkOS, Okta, and Ruby
• SAML SSO with WorkOS, Okta, and Python
• SAML SSO with WorkOS, JumpCloud, and Node

Security considerations

SSO improves security but also requires best practices:

• Replay protection and expiration: SAML assertions and OIDC tokens should include timestamps and nonces to prevent replay attacks. Always validate expiration times and ensure the token or assertion is used only once and within an acceptable window.
• Use provisioning strategy: JIT vs. SCIM
  
  • Just-In-Time (JIT) provisioning creates user accounts at the moment of first login. It’s simple to implement, but doesn’t allow for role-based access ahead of time.
  • SCIM provisioning lets identity providers push user and group data to your app—automatically creating, updating, and deleting accounts as changes occur in the IdP. This ensures access is revoked when an employee leaves, reducing risk.
• Audit trails and logging: Maintain logs of who authenticated, when, and from where. Most IdPs provide event logs, but you should also log authentication events in your app for auditing and incident response.
• Access scopes and permissions: Don’t rely solely on authentication. Enforce application-level authorization controls based on user roles or groups returned in the assertion or token.
• Fallback and lockout handling: Plan for IdP outages or misconfigurations. Offer secure fallback login flows (e.g., admin login bypass or emergency access) and alert systems when authentication fails at scale.

By offloading authentication to trusted IdPs, you reduce the risk of password-based attacks—but you still need to handle provisioning, authorization, and observability. WorkOS helps developers apply secure defaults and implement enterprise-grade security from day one.

!!For more security considerations see SSO best practices.!!

Final thoughts: Why SSO matters for SaaS

SSO is a foundational capability for any SaaS company moving upmarket. It enables frictionless login for users, enforces IT control for buyers, and reduces complexity for developers—especially when paired with a platform like WorkOS.

WorkOS is SOC 2 Type II compliant and provides secure defaults out-of-the-box for SSO authentication and provisioning.

Whether your enterprise customer uses Azure AD with SAML, Google Workspace with OIDC, or anything else, a single WorkOS integration handles them both—turning what used to be a months-long integration into a few days of work.

Sign up today and start authenticating users in minutes.