Single Sign-On (SSO) is an authentication method that allows users to access multiple applications and services after signing in once through a trusted identity provider. Instead of maintaining separate login credentials for every application, users authenticate through one central system and can then access connected applications without repeatedly entering their credentials.
For organizations managing multiple cloud applications, SaaS platforms, internal systems, business tools, or ecommerce portals, SSO can simplify authentication while giving IT teams a centralized way to manage user access and security policies.
But how does SSO actually work, and what happens after a user signs in?
This guide explains how Single Sign-On works, the protocols behind it, its benefits and security considerations, and how SSO can be used in enterprise and B2B ecommerce environments.
What Is Single Sign-On (SSO)?
Single Sign-On allows a user to authenticate once and then access multiple connected applications without having to sign in separately to each one.
For example, an employee may sign in with their company account and then access Microsoft 365, Salesforce, Slack, and other approved applications without entering a separate username and password for each service.
The authentication is handled by a central Identity Provider (IdP). Once the user's identity has been verified, connected applications can recognize that authentication and provide access based on the permissions assigned to the user.
A Simple Way to Think About SSO
Think of SSO like a wristband at a theme park.
You show your ticket at the entrance, your identity or eligibility is checked, and you receive a wristband. You don't need to show your ticket again every time you enter an attraction covered by that wristband.
SSO works in a similar way. The identity provider verifies who you are once, and connected applications trust that authentication instead of asking you to enter your credentials again.
The applications still decide what you are allowed to access, but they don't necessarily need to authenticate you independently.
Identity Provider (IdP) vs. Service Provider (SP)
Two terms commonly appear when explaining SSO:
- Identity Provider (IdP): The system that authenticates the user and manages their identity. Examples include Microsoft Entra ID, Okta, and other identity platforms.
- Service Provider (SP): The application or service the user wants to access. This could be a SaaS application, employee portal, ecommerce platform, or internal business system.
The IdP verifies the user's identity, while the service provider relies on that authentication to provide access.
How Does Single Sign-On Work?
SSO works by creating a trusted relationship between the identity provider and the applications connected to it.
6-Step SSO Authentication Flow
A typical SSO login follows this basic sequence:
User → Application → Identity Provider → Authentication → Authentication Response → Application Access
Here's what happens at each stage:
Step 1: The user open application - The user attempts to access an application that supports SSO.
Step 2: The application redirects the user to the identity provider - Instead of asking the user for application-specific credentials, the application sends the user to the configured IdP.
Step 3: The user authenticates with the IdP - The user may enter a password, use a security key, approve a push notification, or complete another authentication method.
Step 4: The identity provider verifies the user - If authentication is successful, the IdP creates an authentication response for the application.
Step 5: The application validates the response - The application checks that the response came from the expected identity provider and that the information is valid.
Step 6: The application creates a session - Once validation succeeds, the user is signed in and can access the application according to their assigned permissions.
If the user later opens another application connected to the same IdP, they may not need to authenticate again because the IdP already has an active session.
What Is an SSO Token or Assertion?
After the identity provider verifies the user's identity, it sends an authentication response to the application. This response tells the application that the user has been successfully authenticated and can be granted access.
The format depends on the protocol being used. SAML uses an assertion, OpenID Connect uses an ID token, and Kerberos uses a ticket. OAuth 2.0 uses access tokens primarily for authorization rather than authentication.
SSO Protocols: SAML, OIDC, OAuth 2.0 and Kerberos
Different applications and environments can use different protocols to implement SSO. The most common ones include SAML, OpenID Connect, OAuth 2.0, and Kerberos.
SAML
Security Assertion Markup Language (SAML) is widely used for enterprise Single Sign-On, particularly with web-based business applications.
With SAML, the identity provider authenticates the user and sends a SAML assertion to the service provider. The assertion contains information that allows the service provider to determine that authentication was successful.
SAML is commonly found in enterprise environments where organizations connect applications to identity platforms such as Microsoft Entra ID or Okta.
OpenID Connect (OIDC)
OpenID Connect (OIDC) is an authentication protocol built on top of OAuth 2.0.
OIDC allows an application to verify a user's identity and obtain information about the authenticated user. It is commonly used by modern web applications, mobile applications, and services that use APIs.
Instead of relying on SAML assertions, OIDC commonly uses an ID token to communicate authentication information.
OAuth 2.0
OAuth 2.0 is primarily an authorization framework rather than an authentication protocol.
It allows an application to obtain limited access to protected resources without requiring the user to share their credentials with that application.
For example, an application may receive an access token that allows it to access specific API resources.
OAuth 2.0 and OIDC are often used together, but they serve different purposes. OIDC adds an authentication layer to OAuth 2.0 so applications can verify the user's identity.
Kerberos
Kerberos is a ticket-based authentication protocol commonly associated with enterprise networks and Microsoft Active Directory environments.
Instead of repeatedly sending credentials to individual services, Kerberos uses tickets to establish authenticated access between users and services.
It is particularly common in internal enterprise environments rather than modern public-facing web applications.
Understanding the Differences
The protocols may all appear in conversations about SSO, but they aren't interchangeable.
- SAML: Used for Authentication and federated identity in enterprise web applications.
- OIDC: Used for Authentication in modern web and mobile applications.
- OAuth 2.0: Used for Authorization across APIs and protected resources.
- Kerberos: Used for Authentication within internal enterprise networks.
Choosing the right protocol depends on the application, identity provider, architecture, and integration requirements.
What Are the Benefits of Single Sign-On?
SSO can provide benefits for both users and IT teams.
Simpler User Experience
Users don't have to remember and enter different credentials for every application they use.
Once authenticated, they can move between connected applications with fewer login prompts.
Fewer Password-Related Problems
Maintaining fewer application-specific passwords can reduce password fatigue and some password-reset requests.
This can also reduce the tendency for users to reuse passwords across different services.
Centralized Access Management
SSO gives IT teams a central place to manage authentication and apply access policies.
Instead of managing authentication independently in every application, organizations can connect applications to a central identity provider.
Easier Employee Onboarding and Offboarding
When employees join an organization, access to applications can be assigned through centralized identity and group management.
When an employee leaves, their access can be removed from the identity system rather than relying entirely on administrators to disable individual application accounts.
Better Security Policy Enforcement
SSO can work alongside security controls such as Multi-Factor Authentication (MFA), conditional access policies, and centralized monitoring.
This allows organizations to apply consistent authentication requirements across supported applications.
Is Single Sign-On Secure?
SSO can improve security, but it is not automatically secure simply because an organization has implemented it.
Because SSO centralizes authentication, protecting the identity provider becomes especially important.
How SSO Can Improve Security
SSO can help organizations:
- Reduce password reuse
- Centralize authentication policies
- Enforce MFA
- Control application access from a central system
- Remove access more efficiently
- Monitor authentication activity
- Reduce the number of application-specific passwords
Common SSO Security Risks
SSO also introduces risks that organizations need to manage.
A compromised identity provider account can potentially provide access to multiple connected applications. Poorly configured applications, excessive permissions, stolen sessions or tokens, and weak user lifecycle processes can also create security issues.
Common risks include:
- Compromised identity provider accounts
- Excessive user permissions
- Misconfigured SSO applications
- Token or session theft
- Poor provisioning and deprovisioning
- Dependence on the availability of the identity provider
SSO Security Best Practices
Organizations implementing SSO should consider:
- Enabling MFA
- Applying least-privilege access
- Reviewing application permissions regularly
- Monitoring authentication activity
- Keeping certificates and metadata up to date
- Removing access promptly when users leave
- Reviewing user and group assignments
- Testing SSO integrations after configuration changes
SSO should therefore be treated as part of a broader identity and security strategy rather than as a standalone security solution.
SSO vs. IAM, MFA, SCIM and Password Managers
SSO is often confused with other identity and access technologies. Although they work together, they solve different problems.
SSO vs. IAM
Identity and Access Management (IAM) is the broader discipline of managing digital identities and controlling access to systems and resources.
SSO is one capability within an IAM strategy. IAM can include identity management, access policies, authentication, authorization, provisioning, governance, and other identity-related controls.
SSO vs. MFA
Multi-Factor Authentication (MFA) adds additional verification when a user authenticates.
For example, a user might enter a password and then approve a login through a mobile device.
SSO and MFA are not alternatives. They can work together: SSO simplifies access across applications while MFA strengthens the authentication process.
SSO vs. SCIM
System for Cross-domain Identity Management (SCIM) is commonly used to automate user provisioning and deprovisioning between identity systems and applications.
SSO primarily handles authentication, while SCIM helps manage user accounts and their lifecycle.
For example, SSO can allow an employee to sign in to an application, while SCIM can automatically create or remove that employee's account.
SSO vs. Password Managers
A password manager stores and manages credentials for different websites and applications.
SSO works differently. Instead of maintaining separate application passwords, connected applications rely on authentication performed by the identity provider.
Password managers can still be useful for applications that don't support SSO.
SSO for B2B Ecommerce and Multi-Storefronts
SSO isn't limited to employee applications. It can also be useful in B2B ecommerce environments where customers, dealers, distributors, and partners need access to multiple digital systems.
SSO for B2B Ecommerce Customers
A B2B customer may already have an identity managed by their organization.
With SSO, authorized employees can use their company credentials to access a B2B ecommerce portal instead of creating and maintaining a separate ecommerce login.
This can make the login experience easier while giving the business greater control over who can access the portal.
SSO Across Multiple Storefronts
Organizations operating multiple ecommerce storefronts may have customers or employees who need access to more than one site.
For example, a company could operate separate storefronts for different regions, brands, or customer groups.
SSO can provide a consistent authentication experience across those connected storefronts while each storefront continues to manage its own business rules and permissions.
SSO for Dealers, Distributors and Partners
Manufacturers and distributors may need to give external users access to dealer portals, partner systems, product information, ordering platforms, or other business applications.
SSO can help centralize authentication for these users while allowing individual applications to determine what each user or organization can access.
Practical B2B Ecommerce SSO Example
Consider a manufacturer that operates a B2B ecommerce storefront, dealer portal, partner application, and CRM.
Without SSO, users may need separate credentials for each system.
With SSO, an authorized user can authenticate through the organization's identity provider and then access the connected applications without repeatedly signing in.
However, authentication is only one part of the process. The ecommerce platform still needs to determine whether that user can access specific catalogs, pricing, orders, accounts, or storefronts.
SSO handles authentication; application-level authorization determines what the user can actually access.
Common SSO Implementation Challenges
SSO can simplify authentication, but implementation requires careful configuration.
Redirect and Callback Configuration
Applications need the correct redirect or callback URLs to complete the authentication process.
An incorrect URL can cause login failures even when the identity provider configuration is otherwise correct.
SAML Metadata and Certificate Issues
SAML integrations often depend on metadata and certificates.
Expired certificates, incorrect metadata, or mismatched configuration can cause an otherwise working SSO integration to stop functioning.
Attribute and User Mapping
Applications may require specific user information such as email address, name, role, or group.
If the attributes sent by the identity provider don't match what the application expects, users may authenticate successfully but still fail to receive the correct access.
User and Group Assignment
A successful login doesn't automatically mean a user has access to every connected application.
Users may need to be assigned to the application or placed in the appropriate groups before access is granted.
Session and Logout Problems
Different applications can handle sessions, timeouts, and logout differently.
For example, signing out of one application doesn't always mean that every other application connected to the identity provider will immediately terminate its own session.
Provisioning and Deprovisioning
SSO authentication and account provisioning are separate processes.
An organization may need SCIM or another lifecycle-management approach to automatically create, update, and remove user accounts in connected applications.
How to Choose and Implement an SSO Solution
The right SSO approach depends on the applications, identity provider, security requirements, and user population involved.
What to Consider When Choosing an SSO Solution
Before implementing SSO, consider:
- Supported SSO protocols
- Identity provider compatibility
- Application compatibility
- MFA support
- User provisioning and deprovisioning
- Role and group mapping
- Security and access controls
- Logging and monitoring
- Scalability
- Integration requirements
The most suitable solution isn't necessarily the one with the most features. It should support the applications and identity infrastructure your organization actually uses.
How to Implement SSO
A typical SSO implementation involves the following steps:
- Identify the applications that need SSO.
- Select or confirm the identity provider.
- Choose the appropriate authentication protocol.
- Configure the identity provider and application.
- Exchange the required metadata or configuration.
- Map user attributes and groups.
- Assign users and access permissions.
- Test authentication, access, and logout behavior.
- Configure MFA and other security policies.
- Monitor the integration after launch.
Testing is particularly important before moving SSO into production. A user may successfully authenticate but still encounter access problems because of incorrect attributes, permissions, redirects, or application configuration.
Conclusion
Single Sign-On gives users a simpler way to access multiple applications while giving organizations greater control over authentication and access management.
Instead of maintaining separate login processes for every application, SSO allows organizations to centralize authentication through an identity provider and establish trusted connections with supported services.
When implemented correctly, SSO can improve the user experience, reduce password-related problems, simplify employee onboarding and offboarding, and support stronger security controls such as MFA.
For businesses managing multiple enterprise applications, B2B ecommerce platforms, customer portals, or partner systems, SSO can also provide a more consistent authentication experience across connected digital environments.
The key is to treat SSO as more than a login feature. Protocol selection, application configuration, user provisioning, authorization, security policies, and ongoing monitoring all contribute to a successful SSO implementation.
Frequently Asked Questions About SSO
What does SSO stand for?
SSO stands for Single Sign-On. It allows users to access multiple connected applications after authenticating through a central identity provider.
What is SSO in simple terms?
SSO lets you sign in once and access multiple connected applications without entering your credentials separately for each one.
How does SSO work?
SSO works by redirecting the user to an identity provider for authentication. Once the user's identity is verified, the identity provider sends an authentication response to the application, which validates it and grants access.
What is an identity provider in SSO?
An identity provider, or IdP, is the system responsible for authenticating users and managing their digital identities.
Is SSO secure?
SSO can improve security by centralizing authentication and making it easier to enforce controls such as MFA. However, the identity provider must be properly secured because it becomes a central part of the authentication process.
Does SSO replace MFA?
No. SSO and MFA serve different purposes. SSO simplifies access across applications, while MFA adds additional verification during authentication. They are commonly used together.
What is the difference between SAML and OIDC?
SAML and OIDC are both used for authentication, but they use different technologies and are common in different environments. SAML is widely used for enterprise web applications, while OIDC is commonly used by modern web and mobile applications.
Does SSO eliminate passwords?
Not necessarily. SSO reduces the need for users to maintain separate passwords for individual applications, but the identity provider may still use a password as one part of the authentication process.
What happens if the identity provider goes down?
If the identity provider becomes unavailable, users may be unable to start new SSO sessions for connected applications. The exact impact depends on the application's session behavior and architecture.
Can SSO be used for ecommerce?
Yes. SSO can be used for B2B ecommerce storefronts, customer portals, dealer and distributor portals, partner systems, and environments where users need access to multiple connected applications.