OIDC vs SAML: What’s the difference?

Authentication is the backbone of secure digital access. Every time a user logs in to an application, the system needs to verify who they are and whether they should be allowed in. This process sounds simple, but at scale, when thousands of employees, partners, and customers need access to multiple systems it becomes complex.

That’s where identity protocols step in. Two of the most widely used standards are OpenID Connect (OIDC) and Security Assertion Markup Language (SAML). Both are designed to secure user access, prevent unauthorized entry, and enable Single Sign-On (SSO). But while they serve the same purpose, they work differently under the hood.

In this blog, we will break down OIDC vs SAML, explain what each protocol is, why it’s needed, where they overlap, and how they differ. By the end, you’ll have a clear picture of which protocol suits your organization best.

What is SAML?

SAML (Security Assertion Markup Language) is one of the oldest and most widely adopted identity protocols. Developed in the early 2000s, SAML quickly became the standard for enabling Single Sign-On (SSO) in enterprise environments.

SAML provides a secure way for an Identity Provider (IdP) to share authentication and authorization data with a Service Provider (SP). Instead of users remembering multiple usernames and passwords for different applications, SAML enables them to log in once with the IdP and gain access to multiple apps.

The protocol uses XML-based assertions to transmit user attributes like usernames, email addresses, and role information. These assertions tell the Service Provider whether the user is authenticated and what they’re authorized to access.

SAML Login Flows:

• IdP-Initiated SSO: The login process starts at the identity provider. A user signs in to the IdP, selects an app, and the IdP sends authentication data to the SP.
• SP-Initiated SSO: The login process starts at the service provider. A user tries to log in to an app, which redirects the request to the IdP for verification. The IdP confirms the user’s identity and sends the data back to the app.

Why use SAML?

SAML remains relevant today because it solves several critical challenges in enterprise environments:

• Secure single sign-on: Employees can access multiple applications with a single login, reducing the risk of weak or reused passwords.
• Reduced password fatigue: Eliminates the need for managing dozens of credentials across systems.
• Centralized access management: IT teams can enforce policies, manage roles, and de-provision accounts from a central system.
• Compliance and auditability: Logs and audit trails help organizations meet regulatory standards.
• Enterprise adoption: Still widely used in governments, financial services, and legacy IT systems where stability and compliance are paramount.

What is OIDC?

OpenID Connect (OIDC) is a modern identity protocol built on top of the OAuth 2.0 framework. While OAuth was originally designed to handle secure authorization by allowing one application to access resources on another without sharing passwords, OIDC extends this by adding an authentication layer. In simple terms, OAuth answers the question “Can this app access that resource?” while OIDC answers “Who is the user?”.

OIDC has become popular because it is lightweight, flexible, and developer-friendly. It is designed with web, cloud, and mobile environments in mind. It uses JSON Web Tokens (JWTs) to carry identity data, which OIDC calls Claims. Claims include details such as the username, email, or role of a user, which help applications decide what a user can access.

OIDC Terminology:

• Identity Provider (IdP): The system that authenticates the user and issues identity information.
• Relying Party (RP): The application that depends on the IdP to validate the user.
• Claims: Pieces of identity data (like name, email, role, or permissions) shared between the IdP and RP.

OIDC is easier to work with because it uses REST APIs and JSON instead of XML. This makes it a good fit for modern SaaS platforms, cloud-based applications, and mobile apps where speed and simplicity matter.

Why use OIDC?

OIDC addresses the challenges of modern, cloud-first ecosystems where flexibility and scalability are critical:

• Mobile-first design: Works seamlessly with mobile and web applications.
• Ease of implementation: Lighter and simpler than SAML, making it easier for developers to integrate.
• Cloud and SaaS ready: Optimized for modern applications that rely on APIs and cloud services.
• Developer-friendly: Built with JSON and RESTful principles, reducing complexity.
• Rapid adoption: Increasingly the default choice for new applications and services.

How are SAML and OIDC similar?

Despite their differences, SAML and OIDC share common ground as identity protocols. Both were created to solve the same fundamental problem: how to let users securely access multiple applications without logging in again and again. They do this by enabling Single Sign-On (SSO) and by simplifying the way applications verify user identities.

The purpose of both protocols is straightforward: a user authenticates once with an Identity Provider (IdP) and can then access multiple trusted applications without having to re-enter credentials. To make this work, both require a trust relationship between the IdP and the application. In SAML, the application is called the Service Provider (SP), while in OIDC, it is called the Relying Party (RP).

While the terminology differs, the overall login flow is nearly the same in both protocols. Here’s how it typically works:

Basic login flow (IdP-initiated)

1. The user logs in to the Identity Provider.
2. The user selects the application they want to access.
3. The IdP sends the user’s information to the browser.
4. The application receives and verifies the data.
5. The user is granted access.

Alternate login flow (SP/RP-initiated)

1. The user tries to log in directly to the application.
2. The application redirects the login request to the IdP.
3. The IdP verifies the user’s identity.
4. The IdP sends the user’s data back through the browser.
5. The application confirms authorization and grants access.

Both SAML and OIDC follow this general sequence of steps, with the main difference being in the data format and terminology. SAML uses XML and calls the data Assertions, while OIDC uses JSON and calls the data Claims. But from the user’s perspective, the experience feels almost identical: a smooth, secure login without multiple password prompts.

OIDC vs SAML: Key differences

Although both SAML and OIDC enable Single Sign-On and share a similar overall login flow, the way they work under the hood is quite different. Their differences lie in age, data format, terminology, and suitability for specific use cases. Here’s a closer look at how they differ:

SAML

SAML is the older of the two, first introduced in 2005. It uses XML-based assertions to transmit user identity information between an IdP and an SP. The application being accessed is called a Service Provider, and the data being transmitted is called an Assertion.

SAML supports two main flows: IdP-Initiated SSO and SP-Initiated SSO. These flows are well-suited for structured enterprise environments with predefined workflows.

Because of its maturity, SAML is still one of the most widely used SSO protocols in enterprises, governments, and regulated industries. However, its XML-based design makes it heavier and less flexible compared to modern alternatives.

OIDC

OIDC, on the other hand, is built on top of OAuth 2.0 authorization framework and is designed for the modern web. While OAuth allows two applications to securely exchange data, OIDC extends this by adding authentication at the user level.

OIDC transmits user data in JSON format, making it lighter and easier to parse than XML. The application is referred to as a Relying Party, and the transmitted identity information is called a Claim.

The login flows in OIDC resemble those in SAML but use modern web standards and API-first design. OIDC’s simplicity, reliance on RESTful APIs, and developer-friendly structure make it the preferred choice for mobile apps, SaaS platforms, and cloud-native environments.

How to choose between OIDC and SAML?

Choosing the right user authentication protocol depends on your environment, applications, and long-term goals. Here are some key factors to consider:

• Application compatibility: Many apps support only one protocol. Your choice may be dictated by what your apps allow.
• User base: Enterprises with legacy systems and internal apps often rely on SAML. Cloud-first, SaaS, and mobile-focused businesses benefit more from OIDC.
• Implementation complexity: SAML is more complex to set up and maintain, while OIDC is simpler to implement and integrate.
• Scalability and future-proofing: OIDC is flexible, developer-friendly, and expected to dominate future adoption. SAML is still reliable but aging.
• Compliance needs: Regulated industries such as healthcare, finance, and government often stick with SAML due to established compliance frameworks.
• Developer preference: OIDC aligns better with API-driven, microservices-based architectures.

In practice, many organizations may need both. Legacy apps may rely on SAML, while modern applications and cloud services should choose OIDC.

Choose Scalefusion OneIdP for Secure Identity and Access Management

Businesses today need IAM solutions that can support both OIDC and SAML authentication protocols. A modern identity platform should bridge the gap between legacy applications and cloud-native systems, ensuring secure and seamless access regardless of protocol.

Scalefusion OneIdP delivers this by simplifying identity management across old and new applications. It enables Single Sign-On with multi-factor authentication and adaptive authentication, and applies Zero Trust principles to verify every access request and reduce risks.

It integrates easily with enterprise, SaaS, and mobile apps, with a scalable design that supports both legacy systems and cloud environments to ensure secure and reliable access.

Whether your applications rely on SAML or OIDC, Scalefusion OneIdP ensures secure, frictionless access for your workforce. 

See how Scalefusion OneIdP enables secure authentication with SAML and OIDC. 

Schedule a demo now.

FAQs

1. What are Authentication Protocols?

Authentication protocols are standardized methods used to verify a user’s identity before granting access to an application or system. They define how identity data is exchanged securely between an Identity Provider (IdP) and an application, ensuring that only authorized users can log in. Examples include SAML, OIDC, OAuth 2.0, and Kerberos.

2. Why should modern SaaS enterprises choose OIDC over SAML?

Modern SaaS enterprises often prefer OIDC because it is lighter, easier to implement, and works seamlessly with APIs, mobile apps, and cloud-native environments. Unlike SAML, which relies on XML and was designed for older enterprise systems, OIDC uses JSON and REST APIs, making it faster and more flexible for SaaS platforms that need to scale globally.

3. Is OAuth 2.0 and OpenID Connect the same?

No. OAuth 2.0 and OpenID Connect (OIDC) are related but not the same. OAuth 2.0 is an authorization framework that allows applications to access resources on behalf of a user without sharing credentials. OIDC builds on OAuth 2.0 by adding an authentication layer, which verifies the identity of the user. In short, OAuth answers “Can this app access my data?” while OIDC answers “Who is this user?”.

4. What is SAML 2.0?

SAML 2.0 is the latest version of the Security Assertion Markup Language protocol. It provides Single Sign-On (SSO) by enabling an Identity Provider to send XML-based assertions about a user’s identity to a Service Provider. This version improved on earlier releases with features like stronger security, better interoperability, and support for both IdP-Initiated and SP-Initiated login flows.

5. What does SAML Assertion and SAML Response mean?

In SAML, an Assertion is the package of identity data sent from the Identity Provider (IdP) to the Service Provider (SP). It contains information such as the user’s ID, attributes, and authorization details. A SAML Response is the actual XML message that carries the Assertion from the IdP to the SP. In other words, the Response is the “envelope,” and the Assertion is the “content” that verifies the user’s identity.

6. Which one is better, SAML or OIDC?

Neither protocol is universally “better”, the choice depends on your use case. SAML is mature, stable, and still widely used in enterprises, government, and compliance-heavy industries where legacy applications dominate. OIDC is newer, lighter, and better suited for modern SaaS, mobile, and cloud-native environments. Many organizations end up using both, depending on the applications they need to support.