IdP-initiated SSO vs. SP-initiated SSO: Differences & use cases

Picture two employees starting their workday. Sarah opens her browser, goes to the company portal, logs in once, and clicks through to her email, project management tool, and CRM. 

Meanwhile, Mike bookmarks his favorite apps and goes directly to each one, getting automatically redirected to log in only when needed. Both are using single sign-on, but in completely different ways.

What you're seeing is the difference between IdP-initiated SSO (Sarah's approach) and SP-initiated SSO (Mike's way). Most organizations end up choosing one approach or the other based on their security requirements, user preferences, and existing infrastructure. 

The decision matters more than you might think. It affects how quickly employees can access their tools, how much control IT teams have over security, and whether your SSO system becomes a helpful productivity tool or just another thing people have to work around.

Understanding these approaches helps you choose the right SSO strategy for your organization and avoid common implementation headaches that can derail even well-planned rollouts.

What is IdP-initiated SSO?

IdP-initiated single sign-on starts the authentication process from the identity provider (IdP) portal or dashboard. Users begin their day by logging into a central company portal where they can see all available applications and click to launch them.

When someone logs into the IdP first, they authenticate once at this central location. The IdP then sends a SAML (security assertion markup language) assertion or security token to whatever application the user wants to access, proving they've already been verified. The application trusts this token and grants access without asking for additional credentials.

This approach is popular in enterprise environments where organizations want centralized control over application access. IT teams can manage everything from one dashboard, and employees get a consistent experience across all their tools. The workflow is simple: log in once, see your apps, click to access them.

How does IdP-initiated SSO work?

The IdP-initiated SSO flow follows a straightforward process that prioritizes centralized authentication and control.

First, the user navigates to their organization's identity provider portal and logs in with their credentials. The IdP authenticates the user and presents them with a dashboard or list of available applications based on their permissions and role.

When the user clicks on an application from this dashboard, the IdP generates a SAML assertion or security token that contains the user's authentication information and any relevant attributes like their role, department, or permissions. This assertion gets sent directly to the target application.

The service provider receives the assertion, validates it against the IdP's digital signature, and grants the user access based on the information in the token. The user lands directly in the application without having to enter additional credentials.

What is SP-initiated SSO?

SP-initiated single sign-on works the opposite way—users start by trying to access a specific application (the service provider) directly. When they attempt to log into an app they haven't authenticated with yet, the application detects they're not logged in and automatically redirects them to the organization's identity provider.

After the user authenticates at the IdP, they get redirected back to the original application with a token proving their identity. The whole process happens seamlessly, so users can bookmark their favorite apps and access them directly without going through a central portal first.

This approach feels more natural to many users because they can access applications the same way they would any website, that is by going directly to the app they want to use. The authentication happens behind the scenes when needed.

How does SP-initiated SSO work?

The SP-initiated SSO flow starts when a user tries to access an application directly, creating a more intuitive experience for many users who prefer to go straight to the tools they need.

When a user navigates to an application they haven't authenticated with yet, the service provider detects that they're not logged in and automatically redirects them to the organization's identity provider. This redirect includes information about which application the user was trying to access, so the IdP knows where to send them back after authentication.

The user then logs in at the IdP using their credentials. Once authenticated, the IdP generates a SAML assertion or OIDC token that contains the user's authentication information and any relevant attributes. Instead of the IdP pushing this information to the application, the user gets redirected back to the original service provider with this token.

The service provider receives and validates the token, then grants the user access to the application they originally wanted to reach. This round-trip process happens seamlessly, so users end up exactly where they intended to go.

Unify HR and identity management in one platform

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What are the differences between IdP-initiated SSO and SP-initiated SSO?

The two SSO approaches differ in several key ways that affect both user experience and security considerations:

Benefits of using IdP SSO

IdP-initiated SSO offers several advantages that make it attractive for many organizations, particularly those prioritizing centralized control and user experience.

Centralized user authentication

All authentication happens through a single portal, giving IT teams complete visibility into who's accessing what applications and when. This centralization makes it easier to enforce security policies, monitor user activity, and ensure consistent authentication standards across all applications.

Reduced password fatigue

Users only need to remember one set of credentials for their main portal, eliminating the need to manage multiple passwords for different applications. This reduces the likelihood of weak passwords, password reuse, and forgotten login credentials that lead to help desk calls.

Streamlined user provisioning and deprovisioning

When new employees join or leave the organization, IT teams can grant or revoke access to multiple applications from a single location. This centralized control reduces the risk of orphaned accounts and ensures that access changes happen quickly and consistently.

Improved security with MFA integration

Multi-factor authentication (MFA) can be implemented once at the IdP level and automatically applied to all connected applications. Users complete MFA once during their initial login and then access all applications without additional authentication prompts.

Faster app access for employees

Once logged into the portal, users can access multiple applications with single clicks, eliminating the time spent entering credentials for each app. This improves productivity and creates a smoother workflow for employees who use many different tools.

Benefits of using SP-initiated SSO

SP-initiated SSO offers distinct advantages that make it attractive for organizations prioritizing user experience and security flexibility.

Better user-driven access flow

Users can access applications the same way they would any website, which is by going directly to what they need. This natural workflow reduces friction and feels more intuitive, especially for users who have specific applications bookmarked or use direct links from email notifications and collaboration tools.

Improved security session handling

Since authentication happens only when users actually intend to access an application, SP-initiated SSO reduces the risk of unintended access. The service provider can also implement application-specific security policies and session timeouts that align with the sensitivity of the data being accessed.

Compatibility with multiple IdPs

SP-initiated flows work well in environments where users might authenticate through different identity providers depending on their role or organization. This flexibility is particularly valuable for B2B applications that serve customers from multiple companies, each with their own identity systems.

Stronger auditing and logging

The SP-initiated flow creates clear audit trails that show user intent to access specific applications. Since authentication happens in response to actual access attempts, logs provide better visibility into which applications users are actively trying to use versus what they simply have permission to access.

Flexible policy enforcement

Service providers can implement granular security policies that trigger additional authentication requirements based on factors like the sensitivity of the requested data, time of access, or user location. This application-level control complements broader organizational security policies.

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Common use cases for IdP SSO

IdP-initiated SSO works particularly well in specific scenarios where centralized control and user experience are priorities. These include:

SaaS applications

Organizations using multiple software-as-a-service applications (Saas) can provide employees with a single portal that lists all available tools. This is especially valuable for companies that use dozens of different SaaS apps and want to maintain control over which employees can access which services.

Customer-facing applications

Some organizations provide customers or partners with access to multiple applications through a branded portal. This approach works well when you want to control the customer experience and guide users to specific applications based on their subscription level or relationship with your organization.

Remote workforce access

For distributed teams, having a centralized portal where employees can find all their work applications regardless of location or device can improve productivity and ensure consistent security policies are applied.

Common use cases for SP-initiated SSO

SP-initiated SSO excels in scenarios where users need direct, flexible access to applications and where organizations want to maintain application-level control over authentication. That includes:

Customer portals and B2B apps

Organizations serving external customers or partners often prefer SP-initiated SSO because it allows each user to authenticate through their own organization's identity provider. Customers can access your application directly while using their familiar corporate credentials.

Multi-tenant applications

Applications serving multiple organizations benefit from SP-initiated flows because they can dynamically redirect users to the appropriate identity provider based on their email domain or organization. This eliminates the need for users to remember which portal to start from.

Partner and contractor access

When working with external partners, contractors, or temporary users, SP-initiated SSO provides flexibility in how these users authenticate. They can use their own organization's credentials or temporary accounts without requiring access to your internal employee portal.

How to choose the right IdP or SP SSO for your business

Selecting between IdP-initiated and SP-initiated SSO involves evaluating several factors that affect both immediate implementation and long-term success.

• Security requirements: IdP-initiated SSO offers centralized control and consistent policy enforcement, making it easier to implement organization-wide security measures. SP-initiated SSO provides application-level security flexibility but requires more coordination between your IdP and individual applications to maintain consistent policies.

• Technical considerations: Evaluate which SSO protocols your existing and planned applications support. Most modern applications support both SAML and OpenID Connect, but some legacy systems might have limitations. Consider whether you need to support multiple identity providers or external user authentication, which might favor SP-initiated approaches.

• Identity provider selection: Look for solutions that support both SSO initiation methods, giving you flexibility as your needs evolve. Popular options include Rippling, which combines HR and identity management in a unified platform, Okta with its application integrations, and Microsoft Azure AD for organizations already using Microsoft ecosystems.

• Additional factors: Don't forget about scalability, pricing models, user provisioning capabilities, and compliance features. The right choice should handle your current needs while growing with your organization and supporting future requirements.

Simplify identity and access management with Rippling

Rippling takes a different approach to identity and access management software by combining your HR system and identity provider into a single platform. This unified approach eliminates the complex integrations and data synchronization issues that plague traditional IdP solutions.

With Rippling, user identities automatically stay synchronized across HR, devices, and third-party applications. When someone gets hired, changes roles, or leaves the company, their access permissions update automatically across all connected systems. You don't need to worry about orphaned accounts or manually updating user attributes in multiple places.

Rippling's built-in password manager, RPass, provides additional security by letting teams securely store and share credentials for applications that don't support SSO.

What sets Rippling apart is its behavioral detection capabilities. Because the platform understands your employees' roles, locations, and normal work patterns, it can automatically detect and block suspicious login attempts, like someone trying to access sensitive applications from an unusual location or outside normal business hours.

Ready to simplify your identity management? Rippling's unified platform eliminates the complexity of managing separate HR and identity systems, giving you better security with less administrative overhead.

IdP SSO FAQs

What's the difference between an identity provider and a service provider?

An identity provider (IdP) is the system that authenticates users and manages their digital identities. Basically, it's where users prove who they are. A service provider (SP), on the other hand, is an application or service that users want to access. The IdP tells the SP "this user is authenticated and here's what they're allowed to do," while the SP provides the actual application functionality. In simple terms, the IdP handles the "who are you?" question, while the SP handles the "what can you do?" question.

Is SSO secure without MFA?

SSO without multi-factor authentication is more secure than using individual passwords for each application, but it's not as secure as SSO with MFA. The main risk is that if someone compromises the single set of credentials, they gain access to all connected applications. Adding MFA creates an additional security layer that makes it much harder for attackers to gain access even if they steal or guess the primary credentials.

What protocols are used in IdP SSO?

The most common protocols for IdP SSO are SAML (security assertion markup language), OpenID Connect, and OAuth 2.0. SAML is widely used in enterprise environments and handles both authentication and authorization. OpenID Connect is built on OAuth 2.0 and is popular for modern web and mobile applications. The choice of protocol often depends on the applications you're integrating and your specific security requirements.

Do all apps support IdP SSO?

Not all applications support IdP SSO, though most modern business applications do. Legacy applications, custom-built software, and some older systems might not have SSO capabilities. However, many identity providers offer workarounds like password vaulting or browser-based automation to provide some SSO benefits even for applications that don't natively support these protocols. When evaluating applications, SSO support should be a key consideration for new purchases.