“SSO vs JWT vs OAuth 2.0: Which Should You Use?”

10 min readJun 28, 2025

A Big shoutout to Napkin AI for the Visual.

Access control boils down to two questions: “Who are you?” and “What are you allowed to do?” Authentication answers the first. Authorization answers the second. If you’re building software that requires users to log in, you’ll eventually face a critical decision: how to handle authentication. The three dominant solutions — Single Sign-On (SSO), JSON Web Tokens (JWT), and OAuth 2.0 — each solve different problems, and choosing poorly can lead to security vulnerabilities, poor user experience, or unnecessary complexity.

Let’s examine each in depth.

1. Single Sign-On (SSO): The Enterprise Standard

SSO allows users to authenticate once and access multiple applications without re-entering credentials. It’s the digital equivalent of a master key for all your corporate systems.

How SSO Works

User Attempts Access: A user tries to open an application (Service Provider).
Redirection: The app redirects to an Identity Provider (IdP) like Okta or Microsoft Entra ID.
Authentication: The user logs in at the IdP.
Token Issuance: The IdP sends a signed token (SAML assertion or OIDC ID token) back to the app.
Access Granted: The app validates the token and lets the user in.

Protocols

SAML: XML-based, common in legacy enterprise systems. Complex but widely supported.
OpenID Connect (OIDC): Modern, JSON-based, built on OAuth 2.0. Simpler than SAML.

When to Use SSO

✔ Corporate environments (employees accessing email, HR systems, and internal tools)
✔ SaaS platforms (logging into Slack with your Google account)

2. JSON Web Tokens (JWT): The Stateless Solution

JWTs are self-contained tokens that enable stateless authentication. They’re compact, URL-safe, and perfect for APIs.

JWT Structure

A JWT has three parts:

Header: Specifies the algorithm (e.g., HS256 for HMAC-SHA256).
Payload: Contains claims (user ID, expiration time, etc.).
Signature: Ensures the token hasn’t been tampered with.

{
  "alg": "HS256",
  "typ": "JWT"
}
{
  "sub": "user123",
  "name": "John Doe",
  "exp": 1735689600
}

When to Use JWT

✔ Microservices authentication (stateless API calls)
✔ Mobile apps (storing session tokens locally)
✔ One-time tokens (password reset links)

3. OAuth 2.0: The Delegated Access Protocol

OAuth 2.0 is not an authentication protocol — it’s an authorization framework. It lets apps access user data without handling passwords.

Key Roles

Resource Owner: The user (e.g., a Google account holder).
Client: The app requesting data (e.g., a weather app).
Authorization Server: Issues tokens (e.g., Google’s OAuth server).
Resource Server: Hosts protected data (e.g., Google Drive).

Common OAuth Flows

Authorization Code Flow: Most secure, for web apps.
PKCE (Proof Key for Code Exchange): For mobile/native apps.
Client Credentials Flow: Machine-to-machine authentication.

When to Use OAuth

✔ Social logins (“Sign in with Facebook”)
✔ Third-party API access (a fitness app reading your Apple Health data)

Security Considerations

SSO: If the IdP is hacked, all connected apps are at risk.
JWT: If stolen, attackers can impersonate users until expiry.
OAuth: Misconfigured redirect URIs can lead to token theft.

5. When to Use Each?

Need centralized enterprise logins? → SSO (SAML/OIDC).
Building APIs or microservices? → JWT.
Allowing third-party integrations? → OAuth 2.0.

Real-World Examples

SSO: Employees accessing Workday and Salesforce via Okta.
JWT: Netflix services authenticating API requests.
OAuth: Spotify letting a stats app access your listening history.

6. Combining Them

Modern systems often blend these technologies:

OAuth + JWT: OpenID Connect uses OAuth to issue JWTs.
SSO + OAuth: Enterprises use OIDC for SSO (e.g., “Login with Google”).

Final Thoughts

Choosing the right authentication method depends on your use case:

SSO for corporate environments.
JWT for APIs and microservices.
OAuth for third-party integrations.

The best systems often combine them. For example, many companies use OIDC (OAuth + JWT) for SSO.

If you’re still unsure, ask yourself:

Who are my users?
What are they trying to access?
How much security do I need?

Answer those, and the right choice becomes clear.

What are SSO, JWT, and OAuth 2.0, and what are their primary purposes?

SSO (Single Sign-On), JWT (JSON Web Tokens), and OAuth 2.0 are distinct technologies for managing authentication and authorization in digital systems.

SSO (Single Sign-On) allows users to authenticate once with a central Identity Provider (IdP) and gain access to multiple independent applications without re-entering their credentials. Its main purpose is to simplify enterprise logins and improve user experience.
JWT (JSON Web Tokens) are compact, self-contained tokens used for stateless authentication. They are primarily used to secure API calls and enable efficient, scalable authentication in microservices architectures and mobile applications.
OAuth 2.0 is an authorization framework, not an authentication protocol, that enables secure delegated access. Its core purpose is to allow third-party applications to access specific user resources on another service (e.g., a social media profile, calendar data) without the user having to share their password.

How does SSO work, and what are its key advantages and disadvantages?

SSO works by redirecting a user who attempts to access a service provider (SP) to a centralized Identity Provider (IdP) for authentication. Once the user successfully logs in with the IdP, the IdP sends a signed token (like a SAML assertion or an OIDC ID token) back to the SP. The SP then validates this token and grants the user access to the application.

Advantages:

One login for multiple applications: Significantly improves user convenience and reduces password fatigue.
Centralized user management: Simplifies the administration of user accounts and permissions across an organization.
Enhanced security: Users only need to remember one strong password, and IT can enforce consistent security policies.

Disadvantages:

Single point of failure: If the IdP experiences downtime, all connected applications become inaccessible.
Complex setup: Configuring SSO, especially with protocols like SAML or OIDC, can be intricate.
Potential for latency: Involves redirects and communication between the SP and IdP, which can introduce slight delays.

What is the structure of a JWT, and when is it typically used?

A JSON Web Token (JWT) is a compact, URL-safe string composed of three distinct parts, separated by dots:

Header: Contains metadata about the token, such as the type of token (JWT) and the cryptographic algorithm used for the signature (e.g., HS256, RS256).
Payload: Contains “claims,” which are pieces of information about the entity (typically the user) and additional data. Common claims include the user ID (sub), name, and expiration time (exp).
Signature: Created by taking the encoded header, the encoded payload, a secret key, and the algorithm specified in the header, then signing them. This signature is used to verify that the token hasn’t been tampered with and was issued by the legitimate sender.

JWTs are typically used in scenarios requiring stateless authentication and efficient data exchange, such as:

Microservices authentication: Allowing services to authenticate requests without needing to query a central session store.
Mobile app sessions: As an alternative to traditional session cookies for managing user sessions.
One-time tokens: For purposes like password reset links or email verification.

How does OAuth 2.0 facilitate secure third-party access, and what are its core roles?

OAuth 2.0 is an authorization framework that allows a third-party application (the “Client”) to access protected resources on behalf of a user (the “Resource Owner”) from another server (the “Resource Server”) without the user sharing their credentials directly with the client. Instead, the user grants permission to the client via an “Authorization Server,” which then issues an “Access Token” to the client. The client uses this access token to make requests to the Resource Server.

The core roles in an OAuth 2.0 flow are:

Resource Owner: The entity (typically the end-user) who owns the protected data and grants access.
Client: The third-party application that wants to access the Resource Owner’s data (e.g., a photo editor app wanting to access user photos).
Authorization Server: The server responsible for authenticating the Resource Owner, obtaining consent, and issuing access tokens to the Client.
Resource Server: The server that hosts the protected resources (e.g., Google Photos, Twitter API) and accepts access tokens from the Client to grant access.

What are the main security considerations for SSO, JWT, and OAuth 2.0?

Each technology has its own set of security considerations:

SSO: The primary vulnerability lies with the Identity Provider (IdP). If the IdP is compromised, it can lead to a system-wide breach, as it controls authentication for all integrated applications. Proper configuration of SAML/OIDC and strong security practices for the IdP are crucial.
JWT: JWTs are stateless and self-contained, which makes them vulnerable to token theft. If a JWT is stolen (e.g., via Cross-Site Scripting, XSS, if stored in localStorage), it can be used by an attacker until it expires, as there’s no inherent way to revoke it easily before its expiration. Using short expiry times and implementing token blacklisting or refresh token mechanisms are common mitigations. They also do not provide built-in encryption, so HTTPS is essential for secure transmission.
OAuth 2.0: Vulnerabilities often arise from misconfigurations in the authorization flows, particularly involving redirect URIs. Improperly validated redirect URIs can lead to token leakage. Protocols like PKCE (Proof Key for Code Exchange) are essential for mobile and native apps to prevent authorization code interception, and strict validation of all parameters is critical to prevent various injection attacks.

When should one choose SSO, JWT, or OAuth 2.0 for a specific use case?

The choice between SSO, JWT, and OAuth 2.0 depends heavily on the specific requirements of your system:

SSO: Ideal for enterprise-wide login management. Use it when you need to provide a single, unified login experience for employees or users accessing multiple internal or SaaS applications (e.g., a company providing access to Workday, Salesforce, and Slack with one login).
JWT: Best suited for stateless API authentication and microservices. Use it when building highly scalable backend APIs or microservices where session management needs to be offloaded, or when authenticating mobile app sessions where cookies might be less suitable (e.g., Netflix services validating API requests).
OAuth 2.0: Essential for enabling secure third-party integrations and social logins. Use it when you want to allow external applications to access a user’s data on your platform without exposing their credentials directly to the third party (e.g., “Sign in with Google/Facebook” features, or a weather app fetching data from a user’s Google Calendar).

Can SSO, JWT, and OAuth 2.0 be used together, and if so, how?

Yes, these technologies are not mutually exclusive and can often work synergistically in a modern system:

SSO + OAuth 2.0 (via OpenID Connect — OIDC): OpenID Connect is an authentication layer built on top of OAuth 2.0. Enterprises frequently use OIDC for their SSO solutions. Here, OAuth 2.0 handles the authorization process (issuing access tokens), while OIDC adds the authentication component (providing ID tokens to confirm user identity). This allows for enterprise SSO with the flexibility and security features of OAuth 2.0.
OAuth 2.0 + JWT: It is very common for OAuth 2.0 authorization servers to issue JWTs as access tokens (as standardized by RFC 9068). When an OAuth 2.0 flow completes and an access token is granted to the client, this token is often a JWT. The client then uses this JWT to make requests to the Resource Server, which can validate the JWT locally without needing to call back to the Authorization Server, offering performance benefits.

This combination allows for secure delegation of access (OAuth 2.0) with efficient, stateless validation of permissions (JWT).

What are some real-world examples of these technologies in use?

SSO:An employee logs into Microsoft Entra ID (formerly Azure AD) once and automatically gains access to their Office 365 applications (Outlook, Word, SharePoint), Salesforce, and internal HR systems without re-entering credentials.

A user logging into a Zoom meeting using their existing Google Workspace credentials.

JWT:Netflix uses JWTs for authenticating requests between its numerous microservices, allowing them to communicate securely and efficiently without central session lookups.

A mobile banking app using a JWT to maintain a user’s session after initial login, allowing subsequent API calls to be authenticated quickly and scalably.

OAuth 2.0:When you click “Sign in with Facebook” or “Sign in with Google” on a new website, you’re using OAuth 2.0 (and likely OIDC on top).

A third-party music analytics tool requesting permission to access your Spotify listening history. Spotify uses OAuth 2.0 to grant the tool a limited-scope access token without revealing your Spotify password.