SAML vs OAuth vs OIDC - Complete Comparison Guide for 2024

Protocol Comparison

SAML vs OAuth vs OIDC

READING TIME

18 minutes

DIFFICULTY

Intermediate to Advanced

THE EXECUTIVE SUMMARY

SAML is the enterprise SSO standard (XML-based, mature). OAuth 2.0 is for API authorization (JSON-based, modern). OIDC adds authentication to OAuth 2.0 and is replacing SAML for new implementations.

The Travel Analogy: SAML is like an old-school paper passport with visa stamps—detailed, formal, and universally accepted for decades. OAuth 2.0 is like a hotel keycard—it grants access to specific rooms but doesn’t prove your identity. OIDC is like a modern digital passport on your phone—lightweight, verifiable, and contains your identity plus access credentials.

At-a-Glance Comparison

Feature	SAML 2.0	OAuth 2.0	OpenID Connect
Year Released	2005	2012	2014
Primary Purpose	SSO / Authentication	Authorization	Authentication + Authorization
Data Format	XML	JSON	JSON (JWT)
Token Type	SAML Assertion	Access Token	ID Token + Access Token
Transport	HTTP POST / Redirect	HTTP Headers (Bearer)	HTTP Headers (Bearer)
Signature Algorithm	XML DSig (RSA-SHA256)	JWT Signature (RS256/HS256)	JWT Signature (RS256/HS256)
Mobile Support	❌ Poor (XML parsing)	✅ Excellent	✅ Excellent
API Integration	❌ Not designed for APIs	✅ Primary use case	✅ Excellent
Enterprise Adoption	✅ Dominant	✅ Growing	✅ Rapidly growing
Learning Curve	Steep	Moderate	Moderate

Understanding SAML 2.0

Security Assertion Markup Language (SAML) 2.0 has been the enterprise SSO standard for nearly 20 years. It was designed before mobile apps and REST APIs existed.

How SAML Works

1

User Accesses Service Provider (SP)

User tries to access Salesforce (the SP). Salesforce doesn’t have the user’s session.

2

SP Redirects to Identity Provider (IdP)

Salesforce generates a SAML Request (AuthnRequest) and redirects user to Okta (the IdP).

3

User Authenticates at IdP

Okta challenges the user (password, MFA). Once verified, Okta creates a SAML Assertion.

4

IdP Sends SAML Response to SP

The signed SAML Assertion (XML) is POSTed back to Salesforce via the user’s browser.

5

SP Validates and Creates Session

Salesforce validates the signature, checks conditions, and creates a local session for the user.

SAML Assertion Structure

A SAML Assertion contains three key sections:

<saml:Assertion>
  <!-- 1. Subject: WHO is this user? -->
  <saml:Subject>
    <saml:NameID>jane.doe@company.com</saml:NameID>
  </saml:Subject>

  <!-- 2. Conditions: WHEN is this valid? -->
  <saml:Conditions
    NotBefore="2024-01-15T10:00:00Z"
    NotOnOrAfter="2024-01-15T10:05:00Z">
    <saml:AudienceRestriction>
      <saml:Audience>https://salesforce.com</saml:Audience>
    </saml:AudienceRestriction>
  </saml:Conditions>

  <!-- 3. Attributes: WHAT do we know about them? -->
  <saml:AttributeStatement>
    <saml:Attribute Name="firstName">
      <saml:AttributeValue>Jane</saml:AttributeValue>
    </saml:Attribute>
    <saml:Attribute Name="department">
      <saml:AttributeValue>Engineering</saml:AttributeValue>
    </saml:Attribute>
  </saml:AttributeStatement>
</saml:Assertion>

When to Use SAML

✅ Use SAML when:

• Integrating with legacy enterprise apps (Salesforce, Workday, ServiceNow)
• Your IdP and SPs only support SAML
• You need mature, battle-tested SSO
• Compliance requires it (some regulations reference SAML specifically)

❌ Avoid SAML when:

• Building mobile or single-page apps (XML is heavy)
• You need API authorization
• Starting a greenfield project (use OIDC instead)

SAML Deep Dive →

Understanding OAuth 2.0

OAuth 2.0 solved a different problem: delegated authorization. It allows apps to access resources on behalf of users without sharing passwords.

OAuth 2.0 Is NOT for Authentication

This is the most common misconception:

❌ What OAuth 2.0 Tells You	✅ What OAuth 2.0 Actually Does
”This is Jane Doe"	"Bearer of this token can read photos"
"User is authenticated"	"Access is authorized for scope X"
"User’s email is jane@company.com"	"Token expires in 3600 seconds”

OAuth 2.0 Flows

Flow	Use Case	Security Level
Authorization Code	Web apps with backend	✅ High
Authorization Code + PKCE	Mobile apps, SPAs	✅ High
Client Credentials	Machine-to-machine	✅ High
Device Code	Smart TVs, CLI tools	✅ Moderate
Implicit	❌ Deprecated	❌ Insecure
Password Grant	❌ Deprecated	❌ Insecure

When to Use OAuth 2.0 (Alone)

✅ Use OAuth 2.0 when:

• Authorizing API access without user identity
• Machine-to-machine communication (Client Credentials)
• Third-party integrations (Slack bot posting to channels)

❌ Avoid using OAuth 2.0 alone when:

• You need to know WHO the user is (use OIDC)
• Implementing user login (use OIDC)

OAuth 2.0 Deep Dive →

Understanding OpenID Connect

OpenID Connect (OIDC) is an identity layer on top of OAuth 2.0. It answers: “Who is this user?”

OIDC = OAuth 2.0 + Identity

OAuth 2.0 Only	OIDC Adds
Access Token	ID Token (JWT with user identity)
resource scopes	openid, profile, email scopes
Token endpoint	UserInfo endpoint
-	Discovery (.well-known/openid-configuration)
-	Standard claims (sub, name, email)

The ID Token

The ID Token is a signed JWT proving user identity:

{
  "iss": "https://idp.example.com",
  "sub": "user-12345",
  "aud": "your-client-id",
  "exp": 1735142400,
  "iat": 1735138800,
  "auth_time": 1735138795,
  "nonce": "abc123",
  "name": "Jane Doe",
  "email": "jane@example.com",
  "email_verified": true
}

When to Use OpenID Connect

✅ Use OIDC when:

• Implementing user login (SSO)
• You need user profile information
• Building modern web/mobile apps
• Replacing SAML in new projects
• “Login with Google/Microsoft/Okta”

OpenID Connect Deep Dive →

Side-by-Side Protocol Comparison

Token Format

SAML Assertion (XML):

<saml:Assertion xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion">
  <saml:Subject>
    <saml:NameID>jane@company.com</saml:NameID>
  </saml:Subject>
  <ds:Signature>...</ds:Signature>
</saml:Assertion>

• Verbose XML format
• ~2-10 KB typical size
• Requires XML parser

OIDC ID Token (JWT):

eyJhbGciOiJSUzI1NiJ9.
eyJzdWIiOiJ1c2VyLTEyMyIsIm5hbWUiOiJKYW5lIn0.
signature...

• Compact, URL-safe
• ~500 bytes typical size
• Native JSON parsing

Discovery

SAML Metadata:

• Static XML file
• Manually exchanged or hosted at URL
• Contains certificates, endpoints, bindings

OIDC Discovery:

GET https://idp.example.com/.well-known/openid-configuration

• Dynamic JSON document
• Auto-discovered at standard URL
• Lists all endpoints and supported features

Logout

SAML Single Logout (SLO):

• Complex, multi-party coordination
• Often unreliable across vendors
• Requires SAML LogoutRequest/LogoutResponse

OIDC Logout:

• RP-Initiated Logout (redirect to IdP)
• Back-channel logout (server-to-server notification)
• Front-channel logout (iframe-based)
• Generally more reliable

Decision Matrix: Which Protocol Should You Use?

Scenario	Recommended Protocol	Reason
New web/mobile app login	OIDC	Modern, lightweight, excellent tooling
Enterprise SSO to legacy apps	SAML	Legacy apps often only support SAML
API authorization	OAuth 2.0	Designed specifically for API access
”Login with Google”	OIDC	Social providers use OIDC
B2B partner federation	SAML or OIDC	Depends on partner capabilities
Machine-to-machine	OAuth 2.0 (Client Credentials)	No user involved
IoT device authentication	OAuth 2.0 (Device Code)	Designed for limited-input devices
Replacing SAML	OIDC	Modern equivalent with better developer experience

Migrating from SAML to OIDC

Many organizations are migrating from SAML to OIDC. Here’s the strategic approach:

Migration Checklist

1. Inventory SAML Applications

   • Which apps support OIDC in addition to SAML?
   • Which are SAML-only?

2. Configure IdP for Both Protocols

   • Okta, Azure AD, and Auth0 all support SAML and OIDC simultaneously
   • Run both protocols during migration

3. Migrate Apps in Phases

   • Start with apps that already support OIDC
   • Prioritize mobile-accessible apps
   • Leave legacy SAML-only apps for last

4. Update Attribute Mappings

   • SAML attributes → OIDC claims
   • NameID → sub claim
   • Custom attributes → custom claims

5. Test Single Logout

   • OIDC logout behavior may differ from SAML SLO
   • Verify session termination across apps

Claim Mapping Example

SAML Attribute	OIDC Standard Claim
NameID	sub
firstName	given_name
lastName	family_name
email	email
groups	groups (custom claim)
department	Custom claim in ID token

Platform Protocol Support

Major identity platforms support all three protocols:

Microsoft Entra ID

Full support for SAML, OAuth 2.0, and OIDC. Enterprise app gallery with pre-configured SSO.

Okta

Native support for all protocols. Extensive app catalog with SAML and OIDC templates.

Auth0

OIDC-first with SAML support. Developer-friendly SDKs for modern apps.

Keycloak

Open-source with protocol adapters. Can act as broker between SAML and OIDC.

Summary: The Right Protocol for the Job

Choose SAML

For legacy enterprise apps, established B2B partnerships, and when compliance specifically requires it. SAML Guide →

Choose OAuth 2.0

For API authorization, third-party integrations, and machine-to-machine communication. OAuth 2.0 Guide →

Choose OIDC

For new user-facing applications, modern SSO, and replacing SAML in greenfield projects. OIDC Guide →

Use Multiple

Most enterprise IdPs support all protocols. Use the right protocol for each application’s needs. SSO Patterns →

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Master Identity Protocols

Deep dive into SAML, OAuth 2.0, and OpenID Connect with our comprehensive implementation guides.

SAML GuideOIDC Guide