Single Sign-On (SSO) Explained: What It Is, How It Works, and When Your Business Needs It

Every employee at your company logs into multiple systems every day — email, a project management tool, an HR platform, an IT asset tracker, maybe a customer CRM. Each of those systems has its own username and password. And every one of those passwords is a potential security incident waiting to happen.

Single Sign-On, or SSO, solves this. It lets an employee log in once — with their company credentials — and access every connected application without logging in again. One authentication event, one set of credentials, full access to the tools they need.

If you have heard the term and wondered whether it is just an enterprise buzzword or something that actually applies to your organisation, this guide breaks it down clearly.

What SSO actually is

SSO is an authentication method that allows users to verify their identity once and then access multiple applications or services without re-entering credentials for each one.

The key concept is a centralised identity provider (IdP) — a system that your business trusts to verify who someone is. Examples include Microsoft Entra ID (formerly Azure AD), Google Workspace, Okta, and OneLogin. When an employee logs into a connected app, the app does not ask them for a password. Instead, it asks the identity provider: "Is this person who they say they are?" The IdP confirms it, and the employee is in.

From the employee's perspective, SSO feels like magic. They sign in at the start of the day and everything just works. From a security perspective, what is actually happening is a much more controlled and auditable authentication process than a collection of individual passwords.

How it works in practice

When an employee tries to access a connected application — say, your IT asset management platform — the application checks whether they already have an active session with the identity provider.

If they do, access is granted immediately. If they do not, the application redirects them to the identity provider's login page. The employee authenticates there, and the IdP issues a secure token confirming their identity. The application reads the token and grants access — without ever seeing or storing the employee's password.

• Employee visits a connected app (e.g. IT Trackr, Slack, Salesforce)
• App redirects to the identity provider (e.g. Microsoft Entra ID or Google Workspace)
• Employee logs in once at the identity provider
• IdP issues a secure token confirming identity
• App reads the token and grants access — no separate password required
• All subsequent connected apps skip login entirely for the duration of the session

The security case for SSO

Most organisations that experience a data breach can trace it back to credentials — either stolen, reused, or weak passwords. SSO does not eliminate credentials, but it dramatically reduces the attack surface.

• Fewer passwords means fewer attack vectors — employees maintain one set of credentials instead of dozens
• Centralised enforcement — MFA policies, password strength requirements, and session timeouts are applied once at the identity provider, not app by app
• Faster offboarding — revoking access to the identity provider immediately cuts access to every connected application simultaneously; no more hunting through 20 systems when someone leaves
• Audit trail — every login across every connected application flows through one system, giving you a complete and searchable authentication log
• Reduced shadow IT — employees are less likely to create personal accounts in unsanctioned tools when company SSO is quick and available

The productivity case for SSO

Password fatigue is real. Research consistently shows that employees reuse passwords across systems, choose simple passwords, and spend significant time on password resets. One study estimated that the average employee spends 11 minutes per day on password-related issues.

SSO eliminates that friction. Employees log in once in the morning and move between tools without interruption. New starters are productive from day one — IT provisions their identity provider account and access to every connected app is immediately available. No need to create accounts in a dozen separate systems and distribute credentials.

SSO protocols: SAML, OIDC, and OAuth

If you start researching SSO you will quickly encounter three acronyms: SAML, OIDC, and OAuth. They are all authentication or authorisation protocols, and most modern SSO deployments use at least one of them.

SAML (Security Assertion Markup Language) is the older, enterprise-focused standard. It uses XML-based tokens and is widely supported by legacy enterprise software. If your business uses Salesforce, ServiceNow, or traditional enterprise applications, SAML is likely involved.

OIDC (OpenID Connect) is the modern standard built on top of OAuth 2.0. It is lighter, uses JSON tokens (JWTs), and is the protocol behind "Sign in with Google" and "Sign in with Microsoft" buttons on modern applications. If you are evaluating newer SaaS tools, they almost certainly support OIDC.

OAuth 2.0 is technically an authorisation protocol rather than an authentication one, but it underpins OIDC and is used by many applications for delegated access. The distinction matters mainly to developers integrating SSO rather than IT teams evaluating it.

When does your business need SSO?

SSO is not the right fit for every organisation at every stage. Here are the signals that suggest it is time to take it seriously.

• Your team uses five or more SaaS applications — the more tools, the more painful password management becomes
• You are spending meaningful time on offboarding — removing access from multiple systems when employees leave is slow and error-prone without SSO
• You have had a security incident involving compromised or reused passwords
• Your compliance framework (ISO 27001, SOC 2, GDPR) requires demonstrable access controls and audit logs
• You are onboarding employees frequently and the setup process takes too long
• Your team works remotely — distributed teams are more reliant on SaaS and more exposed to credential-based attacks

What to look for when evaluating SSO

• Protocol support — check that your key applications support SAML or OIDC; most modern SaaS tools do
• MFA integration — SSO without MFA solves the wrong problem; the identity provider should enforce multi-factor authentication centrally
• Directory integration — can you sync users from your existing directory (Microsoft Entra ID, Google Workspace, LDAP)?
• Automated provisioning and deprovisioning (SCIM) — the best setups automatically create and remove accounts in connected apps when users are added or removed in the directory
• Pricing model — some identity providers charge per user per month; evaluate total cost against the time saved on IT administration
• Application coverage — your identity provider should offer pre-built connectors for the tools you already use

Getting started

If your organisation already uses Microsoft 365 or Google Workspace, you already have an identity provider. Microsoft Entra ID and Google Workspace both support SAML and OIDC SSO and connect to thousands of applications out of the box.

The practical first step is an audit: list every application your team uses, check which ones support SSO, and identify the identity provider that covers the most ground. For most small and medium businesses, Microsoft Entra ID or Google Workspace is the obvious starting point because they are already paying for it.

Prioritise the applications that hold the most sensitive data first. Then expand the SSO footprint over time, moving accounts off individual passwords as you go.