What Is SSO? Single Sign-On, Explained

SSO (Single Sign-On) lets a person sign in once and reach several applications without logging in again. A central identity provider verifies the user, then vouches for them to each connected app for the length of the session.

One login replaces many. Users stop juggling a separate password for every tool, and the organization gets one place to enforce policy: multi-factor authentication, password rules, and instant revocation when someone leaves. Most workplace software supports it, from email and document suites to specialized line-of-business tools.

SSO relies on a trust relationship between the identity provider and each application. Standard protocols carry that trust, most commonly SAML and OpenID Connect (which builds on OAuth 2.0). The application never sees the user's password; it receives a signed assertion or token confirming who they are.

A logistics operator with a transportation management system (TMS), a warehouse app, and a customer portal is a typical case. Staff sign in through one company account and move between the three without re-entering credentials, while IT keeps a single audit trail of who accessed what.

SSO handles authentication, proving who you are. It does not decide what you may do once inside; that is authorization, often handled by RBAC.

Why it matters for custom software

When we build software that a client's team logs into daily, we connect it to their existing identity provider rather than creating one more password to manage. That keeps security centralized and onboarding quick, a common requirement in IT and internal platforms.

This page is a definition, not security advice.