SSO lets your employees log in once and access all their work applications without signing in again — which is better for productivity, better for security, and better for your IT team's sanity.
Filed under the NerdSquad IT Dictionary. SSO is one of those technologies that's been quietly running under the hood of enterprise IT for years and is now standard in most Microsoft 365 and cloud-first environments. Here's what it actually means and why it matters.
SSO = Single Sign-On. A system that lets a user authenticate once — typically at the start of their workday or when they open their laptop — and then access all connected applications without being prompted to log in again for each one.
Without SSO, logging into work looks like this: sign into Windows, sign into email, sign into the practice management system, sign into the billing platform, sign into the HR portal, sign into the file sharing tool. Each one has its own username and password. Some require MFA separately. By mid-morning, your staff has entered credentials six times and forgotten two of them.
With SSO, it looks like this: open the laptop, authenticate once (password plus an MFA prompt), and everything else just opens. The authentication event at the beginning of the session is trusted across all connected applications for the duration of that session.
It's the difference between a keychain with one master key and a keychain with seventeen different keys for seventeen different doors.
SSO is built on identity protocols — SAML, OAuth, and OpenID Connect are the most common — that allow applications to delegate authentication to a central identity provider (IdP) rather than managing it themselves.
In practice for most businesses: Microsoft Entra ID (formerly Azure Active Directory) is the identity provider. When a user tries to open an application — Teams, SharePoint, a third-party SaaS tool, a line-of-business app — that application checks with Entra ID: "Is this user authenticated?" If yes, the user gets in without a separate login. If not, they're prompted to authenticate with Microsoft first, and then they're in.
The central identity provider also enforces security policies: MFA requirements, conditional access rules, device compliance checks, and session timeouts. All of it managed in one place rather than separately in each application.
This surprises some people. "Isn't one password worse than many?" Not in practice, for a few reasons.
HIPAA, PCI-DSS, and most other compliance frameworks require access controls, audit logging of authentication events, and prompt revocation of access when employees leave. SSO makes all of these easier to implement correctly and easier to demonstrate to an auditor. A centralized identity provider with a complete authentication log is a significantly cleaner compliance posture than a collection of application-specific credentials managed inconsistently across the organization.
For most business clients, SSO implementation means configuring Microsoft Entra ID as the identity provider and connecting business-critical applications to it — both Microsoft 365 applications natively and third-party applications through SAML or OAuth integrations. We pair SSO with MFA and conditional access policies as part of a Zero Trust identity architecture. It's one of the highest-leverage configurations we make in a new client environment.