What Is Single Sign-On (SSO)? How It Works & Why Businesses Need It

Single sign-on (SSO) is an authentication method that allows users to log in once with a single set of credentials and gain access to multiple applications and systems without signing in again. Instead of remembering separate usernames and passwords for every application you use, SSO lets you authenticate once and move seamlessly between services.

In simple terms: SSO means one login for everything. You sign into your company's identity provider (like Microsoft Entra ID or Okta) once in the morning, and you can access your email, CRM, project management tools, HR system, and every other application without entering credentials again.

With the average employee using 27 different applications at work (Productiv, 2025) and password fatigue being a leading cause of weak security practices, SSO has become a foundational component of modern business IT. This guide explains how SSO works, the protocols behind it, and how to implement it effectively.

How Single Sign-On Works

SSO works by establishing a trusted relationship between an identity provider (IdP) — the central system that verifies who you are — and service providers (SPs) — the applications you want to access. Here is the step-by-step process:

The SSO Login Flow

1. User attempts to access an application (e.g., opens Salesforce)
2. Application redirects to the identity provider — Salesforce recognizes the user has not authenticated and redirects them to the company's IdP (e.g., Microsoft Entra ID)
3. IdP checks if user has an active session — if the user already logged in today, the IdP recognizes the existing session
4. If no session exists, user authenticates — enters username, password, and completes MFA
5. IdP generates a security token — a signed assertion (SAML token or OAuth token) that proves the user's identity and what they are authorized to access
6. Token is sent to the application — the application validates the token's signature against the IdP's public key
7. Access is granted — the user is logged into Salesforce without entering Salesforce-specific credentials
8. Subsequent applications skip authentication — when the user opens another SSO-enabled app (e.g., Slack), steps 2-6 repeat instantly using the existing IdP session, with no additional login required

The key concept is that the user only enters their credentials once (at the IdP). Every subsequent application receives a token proving the user's identity — the password never leaves the IdP.

SSO Protocols Explained

SSO relies on standardized protocols that define how identity providers and service providers communicate. The three most important protocols are:

SAML 2.0 (Security Assertion Markup Language)

The most widely used protocol for enterprise SSO. SAML exchanges XML-based authentication assertions between the IdP and SP.

• Best for: Enterprise web applications, B2B integrations
• How it works: User visits app → app redirects to IdP → IdP authenticates user → IdP sends signed XML assertion (SAML response) to app → app grants access
• Used by: Salesforce, Workday, ServiceNow, AWS Console, and most enterprise SaaS applications
• Limitation: XML-based, making it heavier than newer protocols. Primarily designed for web browsers, not mobile apps or APIs.

OAuth 2.0 and OpenID Connect (OIDC)

OAuth 2.0 is an authorization framework, and OpenID Connect (OIDC) adds an identity layer on top. Together, they provide SSO capabilities using lightweight JSON Web Tokens (JWTs) instead of XML.

• Best for: Modern web applications, mobile apps, APIs, consumer-facing applications
• How it works: User visits app → app redirects to IdP → IdP authenticates user → IdP returns an ID token (JWT) and access token → app validates token and grants access
• Used by: Google Sign-In, "Sign in with Apple," "Sign in with Microsoft," GitHub, Slack API, modern SaaS applications
• Advantage: Lightweight, mobile-friendly, and supports both authentication and API authorization

LDAP (Lightweight Directory Access Protocol)

An older protocol used primarily for on-premises SSO with Active Directory. When you log into a Windows computer and automatically have access to file shares, printers, and internal applications — that is LDAP-based authentication.

• Best for: On-premises environments, Windows Active Directory networks
• Limitation: Not designed for cloud/SaaS applications. Being replaced by SAML and OIDC for modern SSO deployments.

Protocol Comparison

Protocol	Format	Best For	Modern Relevance
SAML 2.0	XML	Enterprise web apps, B2B	Still dominant in enterprise — most SaaS apps support it
OIDC/OAuth 2.0	JSON (JWT)	Modern apps, mobile, APIs	Growing rapidly — preferred for new applications
LDAP	Binary	On-premises Active Directory	Legacy — being phased out in favor of cloud protocols

Benefits of Single Sign-On

1. Stronger Security

This seems counterintuitive — one login for everything sounds like a bigger risk. But SSO actually improves security by:

• Eliminating password fatigue: Users who manage 27+ passwords inevitably reuse them. SSO reduces passwords to one strong credential.
• Enabling MFA enforcement: With SSO, you enforce MFA at one point (the IdP) and it protects every application behind it.
• Reducing the attack surface: Fewer passwords means fewer opportunities for phishing, credential stuffing, and brute force attacks.
• Centralizing access control: When an employee leaves, disabling their SSO account immediately revokes access to every connected application.

2. Improved User Productivity

Employees spend an average of 11 hours per year entering and resetting passwords (LastPass). SSO eliminates this friction entirely. Users log in once and access everything — no remembering passwords, no password reset interruptions, no lockouts from failed login attempts.

3. Reduced IT Support Costs

Password resets account for 20-50% of all helpdesk tickets (Gartner). With SSO, users have one password to manage, and that password is backed by MFA — dramatically reducing lockout and reset requests. For a 500-person organization, this can save hundreds of helpdesk hours annually.

4. Simplified Compliance

SSO provides centralized audit logs showing who accessed what applications and when. This simplifies compliance reporting for SOC 2, HIPAA, PCI DSS, and GDPR by providing a single source of truth for access records instead of scattered logs across dozens of applications.

5. Faster Onboarding and Offboarding

With SSO, onboarding a new employee means creating one identity provider account and assigning application access. Offboarding means disabling one account to revoke all access. Without SSO, IT must create and disable accounts in each individual application — a process that is error-prone and often incomplete (leading to orphaned accounts that remain accessible).

Risks and Challenges of SSO

1. Single Point of Failure

If the identity provider goes down, users cannot access any SSO-connected application. This is why IdP availability is critical — choose providers with 99.99%+ uptime SLAs and geographic redundancy. Microsoft Entra ID, Okta, and Google Workspace all offer this level of reliability.

2. Single Point of Compromise

If an attacker compromises an SSO account, they gain access to every connected application. This is why SSO must always be paired with strong MFA — especially phishing-resistant methods like FIDO2 keys for high-privilege accounts. SSO without MFA is worse than no SSO at all.

3. Not All Applications Support SSO

Older or niche applications may not support SAML or OIDC. Some SaaS vendors charge a premium for SSO support (the so-called "SSO tax"), with some charging $3-$10 more per user per month for SSO-enabled plans. This has been widely criticized by the security community and is slowly changing.

4. Implementation Complexity

Configuring SSO between an IdP and each service provider requires technical setup — configuring SAML assertions, mapping user attributes, testing login flows, and handling edge cases. For organizations with 20+ applications, the initial rollout can take several weeks.

Top SSO Providers

Provider	Best For	Starting Price	Key Features
Microsoft Entra ID (Azure AD)	Microsoft 365 organizations	Free with M365 (Premium P1: $6/user/mo)	Deep M365 integration, conditional access, 3,000+ pre-integrated apps
Okta	Multi-cloud, platform-agnostic	$2/user/mo (SSO only)	7,400+ pre-built integrations, advanced lifecycle management
Google Workspace	Google-centric organizations	Included with Workspace	Google ecosystem integration, SAML/OIDC support
JumpCloud	SMBs, hybrid environments	Free for 10 users	Directory, SSO, and MDM in one platform
OneLogin	Mid-market, ease of use	$4/user/mo	Quick setup, strong SAML support, risk-based auth
Duo (Cisco)	MFA-first approach with SSO	$3/user/mo	Leading MFA combined with SSO, strong Cisco integration

For most MSP clients running Microsoft 365, Microsoft Entra ID is the natural SSO choice because it is already included in their M365 subscription. Business Premium and E3/E5 plans include Entra ID Premium P1, which provides conditional access, group-based app assignment, and self-service password reset — covering most SSO needs without an additional vendor.

SSO vs Password Manager

Another common question: should you use SSO, a password manager, or both?

Feature	SSO	Password Manager
How it works	One login grants access to all connected apps via tokens	Stores unique passwords for each app in an encrypted vault
User experience	Seamless — no passwords for individual apps	Good — autofills passwords, but user must still "log in" to each app
Security model	Centralized authentication, tokens, no passwords shared with apps	Each app still receives a password (unique, but still a password)
IT control	Full — centralized provisioning, deprovisioning, audit logs	Limited — IT can manage the vault but not individual app sessions
Coverage	Only apps that support SAML/OIDC (enterprise apps)	Any app with a login form (including personal sites)
Best for	Business applications — primary solution	Apps that do not support SSO — secondary solution

Best practice: Use SSO as the primary authentication method for all applications that support it. Use a password manager (1Password Business, Bitwarden, Keeper) for the remaining applications that do not support SSO. This two-layer approach covers your entire application portfolio.

Implementing SSO for Your Business

Step 1: Inventory Your Applications

List every application your organization uses. For each one, determine whether it supports SAML, OIDC, or neither. Most major SaaS applications support at least one SSO protocol — check each vendor's documentation.

Step 2: Choose Your Identity Provider

If your organization already uses Microsoft 365, start with Microsoft Entra ID. If you use Google Workspace, start with Google's built-in IdP. Only add a third-party IdP (Okta, JumpCloud) if you need features your existing platform does not provide.

Step 3: Configure SSO for Critical Applications First

Start with the applications used by the most people and carrying the most risk:

• Email and productivity (Microsoft 365, Google Workspace)
• CRM (Salesforce, HubSpot)
• Communication (Slack, Zoom)
• Cloud platforms (AWS Console, Azure Portal)
• HR and finance systems

Step 4: Enforce MFA at the IdP Level

SSO without MFA is a security liability. Configure conditional access policies at the IdP to require MFA for all users, especially:

• Sign-ins from new devices or locations
• Access to sensitive applications (finance, HR, admin consoles)
• All admin and privileged accounts (always require MFA, no exceptions)

Step 5: Disable Direct Application Logins

After SSO is configured, disable the ability to log into applications with a direct username/password. If users can bypass SSO, they will — and you lose the security and audit benefits. Most enterprise SaaS applications allow admins to enforce "SSO only" authentication.

SSO for MSPs

For managed service providers, SSO is both a security best practice to implement for clients and a business differentiator:

Client SSO Implementation

• Microsoft 365 SSO: Most MSP clients run M365 and can use Entra ID for SSO at no additional cost. Configuring SSO for all client SaaS applications through Entra ID is a high-value service.
• Conditional access policies: Build standardized conditional access templates that can be deployed across all client tenants — enforcing MFA, blocking risky sign-ins, and requiring compliant devices.
• User lifecycle automation: Connect SSO with provisioning/deprovisioning workflows so that adding a user to a group in the IdP automatically provisions their accounts in connected applications.

MSP-Specific SSO Challenges

• Multi-tenant management: Configuring and maintaining SSO across 20, 50, or 100+ client tenants requires efficient processes and tooling
• Diverse application landscapes: Each client uses a different mix of applications, and not all support SSO
• User training: Educating end users across all client organizations about the new login experience
• Ongoing maintenance: SSO certificates expire, application configurations change, and new applications need to be integrated

Managing SSO and identity across dozens of client tenants requires deep Microsoft 365 and identity management expertise. White-label Microsoft 365 support provides MSPs with certified administrators who handle Entra ID configuration, SSO setup, conditional access policies, and ongoing identity management under your brand — so you can offer enterprise-grade identity services without building a specialized team.

Frequently Asked Questions

What is single sign-on?

Single sign-on (SSO) is an authentication method that lets you log in once with one set of credentials and access multiple applications without signing in again. Instead of managing separate usernames and passwords for your email, CRM, project management tool, and other work applications, you authenticate once through a central identity provider and all connected applications recognize your identity automatically.

What is an example of single sign-on?

A common example: you log into Microsoft Entra ID (Azure AD) in the morning using your email and password plus an MFA prompt. Then you open Salesforce, Slack, Zoom, and Jira throughout the day — each one recognizes your identity automatically without asking for a separate login. Another consumer example: using "Sign in with Google" to access multiple websites without creating separate accounts for each one.

Is SSO more or less secure than regular passwords?

SSO is more secure when implemented correctly with MFA. It reduces the number of passwords users manage (eliminating password reuse), centralizes authentication (making MFA easier to enforce), and simplifies deprovisioning (disabling one account revokes all access). However, SSO without MFA creates a dangerous single point of compromise — if the one password is stolen, every connected application is exposed. Always pair SSO with strong MFA.

What is the difference between SSO and MFA?

SSO and MFA solve different problems and work together. SSO (single sign-on) reduces the number of logins by letting you authenticate once and access many applications. MFA (multi-factor authentication) strengthens each login by requiring multiple forms of verification. The best practice is to use both: SSO for convenience and centralized control, MFA at the SSO login point for security. They are complementary, not competing technologies.

How much does SSO cost?

SSO costs vary by provider. Microsoft Entra ID provides basic SSO free with any Microsoft 365 plan; premium features (conditional access, advanced reporting) require Entra ID Premium P1 at $6/user/month (included in M365 Business Premium). Okta starts at $2/user/month for SSO only. JumpCloud offers free SSO for up to 10 users. Some SaaS vendors charge a premium for SSO support on their end, typically $3-$10/user/month extra.

Key Takeaways

• Single sign-on lets users authenticate once and access all connected applications without additional logins.
• SSO improves security by reducing password fatigue, enabling centralized MFA enforcement, and simplifying deprovisioning.
• SAML 2.0 is the dominant enterprise SSO protocol; OIDC/OAuth 2.0 is growing for modern and mobile applications.
• SSO must always be paired with MFA — SSO without MFA creates a dangerous single point of failure.
• For M365 organizations, Microsoft Entra ID provides SSO capabilities included in the existing subscription.
• MSPs can implement and manage SSO across client tenants through white-label Microsoft 365 support with certified identity management professionals.