What is OIDC?
OpenID Connect (OIDC) is a modern authentication protocol built on the OAuth 2.0 framework. While OAuth 2.0 focuses on authorization by determining what a user can access, OIDC goes a step further by establishing a standardized way to verify who the user actually is.
Because OIDC is built on a widely used open standard, it works effortlessly across different platforms, applications, and identity providers. This makes it a practical choice for organizations looking to unify how users sign in.
Key components of OIDC
OIDC is built around a set of core components that work together to establish a secure and standardized authentication experience.
Relying party (RP)/client
This is an application, such as a web, mobile, or desktop app, that transfers the responsibility of user authentication to a trusted OpenID provider. Rather than verifying user identity directly, the relying party trusts the provider to do so and acts on the result.
OpenID provider (OP)
This is the central identity service in OIDC. It verifies the user’s identity and communicates the outcome to the relying party. The user typically already holds an account with the OP.
Access token
An access token allows the relying party to access specific resources or retrieve user information on behalf of the authenticated user.
Refresh token
This optional token enables the relying party to obtain a new access token once the previous one expires, keeping the session active without requiring the user to sign in again.
UserInfo Endpoint
A protected resource provided by the OpenID provider that returns additional user claims approved during authentication, such as a user’s name, email address, or profile information. The relying party retrieves this information using an access token.
How OIDC works for secure user authentication
OIDC enables a user to sign in through a trusted identity provider and gain access to a separate application, without creating a new set of credentials. The process relies on three key elements.
Identity token (ID token): JSON web tokens (JWTs) are issued by the OpenID provider after successful authentication. They contain claims about the authenticated user and serve as proof of identity for the relying party.
Scopes: Parameters included in an authentication request define the level of access and the user information the relying party is requesting from the OpenID provider.
Claims: The individual pieces of user information contained within the identity token, such as name, email address, and profile details.
The following steps outline how OIDC authentication works in practice:
- A user tries to access a website or web application via their browser.
- The user selects the sign-in option and submits their username and password.
- The relying party forwards an authentication request to the designated OpenID provider.
- The OpenID provider verifies the user’s identity and ensures that the necessary authorization is granted.
- The OpenID provider returns an ID token and, depending on the requested scopes and flow, may also issue an access token.
- The relying party validates the ID token and may use the access token to retrieve additional user information from the UserInfo Endpoint.
- The identity provider’s user information service returns the approved user details (such as name and email) to the relying party, which then grants the user access to the application.
What are the different OIDC flows?
OIDC supports multiple authentication flows, each suited to a specific type of application. The right flow depends on whether the client is public (single-page applications [SPAs], mobile, and native apps that cannot store secrets securely) or confidential (server-side apps that can).
OIDC flow | Best suited for | How it works | Example |
Authorization code flow | Server-side web applications | The OpenID provider issues an authorization code that the relying party exchanges for tokens, including an ID token used to verify the user’s identity. Tokens are never exposed to the browser, making it the most secure option for confidential clients. | A user signing into Zoho CRM through Zoho Directory using their organization credentials. |
Authorization code flow with proof key for code exchange (PKCE) | Mobile, native, and single-page applications | Extends the authorization code flow by adding a code verifier and code challenge to prevent interception. Recommended for public clients that cannot store secrets securely. | A user authenticating into the Zoho Mail mobile app through Zoho Directory. |
Client credentials flow | Backend services and automated processes | The application authenticates using its own credentials with no user interaction involved. Commonly used for machine-to-machine communication. | GitHub Actions authenticating with the GitHub API to automatically trigger builds, run tests, and deploy code without any user sign-in. |
Device code flow | Smart TVs, Internet of Things (IoT), and devices with limited input options | The user authenticates on a separate browser-enabled device and the application receives access once authorization is complete. | A user signing into a browser-limited enterprise device by completing authentication on their phone or computer. |
OIDC vs. SAML vs. OAuth 2.0
While OIDC, SAML, and OAuth 2.0 are all widely used in identity and access management, they serve distinct purposes and are suited to different scenarios.
The table below outlines the key differences to help organizations choose the right protocol.
Key aspect | OIDC | SAML | OAuth 2.0 |
Primary purpose | Authentication protocol based on OAuth 2.0 with an integrated identity layer | Authentication and authorization standard built for enterprise SSO | An authorization framework that controls and delegates access to protected resources |
What it provides | Verifies who the user is and enables SSO across applications | Verifies user identity and passes assertions between identity and service providers | Controls what the user or application is permitted to access |
Token/assertion format | JWT; a JSON-based ID token | SAML assertion in XML format | JSON-based access token |
Best suited for | Modern web, mobile, and native applications | Enterprise environments with legacy systems and federated identity requirements | API security and delegated authorization between services |
SSO support | Enables users to sign in once and access multiple connected applications without re-authenticating | Widely adopted for enterprise SSO across both on-premise and cloud applications | Not supported natively, requires the addition of OIDC or SAML |
Mobile app support | Fully supported and the preferred choice for mobile and single-page applications | Limited due to its XML-based structure, which is less suited to mobile environments | Supported, particularly when paired with PKCE for secure token exchange |
Zoho Directory support | Supported via OIDC application integration in Zoho Directory | Supported via SAML application integration in Zoho Directory | OAuth 2.0 forms the foundation of Zoho Directory’s OIDC implementation |
Key benefits of OIDC
OIDC offers measurable advantages to both users and organizations. These range from stronger security to a simpler and more consistent sign-in experience.
Reduced password dependency
OIDC enables single sign-on, allowing users to authenticate once and access all connected applications without re-entering their credentials. This reduces password fatigue, minimizes login friction, and keeps users focused on their work rather than managing multiple accounts.
Centralized security enforcement
By centralizing authentication through a trusted identity provider, organizations can enforce consistent security controls. This extends to multi-factor authentication for all connected applications. Users verify their identity through multiple factors, such as a password, a trusted device, or a biometric, significantly reducing the risk of unauthorized access.
Credential-free access for applications
OIDC uses cryptographically signed tokens to validate user identity, meaning applications never directly handle or store user passwords. This limits exposure to threats such as credential theft and phishing, while token expiration and scopes ensure that access remains time-bound and purpose-specific.
Interoperability across platforms
Built on open standards, OIDC works consistently across web, mobile, and enterprise environments. It integrates with major identity providers and supports a wide range of platforms and libraries, making it a reliable choice for organizations operating across hybrid or multi-cloud environments.
Simplified identity management
Organizations using OIDC for single sign-on can consolidate identity management into a single interface. This makes it easier to track permissions, apply access policies, and manage user identities across multiple applications.
Privacy and compliance
Through scopes and claims, OIDC gives users control over what information they share with each application. This consent-based approach to data access supports compliance with global privacy regulations and helps organizations build user trust.
Common use cases and examples of OIDC
OIDC is widely adopted across industries to enable secure, consistent authentication for both consumer and enterprise applications. Here are a few examples of how it’s used in practice.
Social sign-in and federated authentication
When a user signs up for an application and is offered the option to continue with Google or Facebook, they’re authenticating through OIDC. The application redirects the user to their chosen identity provider, which verifies their identity and shares approved profile details, such as name and email, with the application. The user gains access without creating a new set of credentials, and their password remains with the identity provider.
Unified access for enterprise applications
A company wants its employees to access multiple work applications, such as Zoho CRM, Zoho Mail, Zoho Analytics, and third-party tools, without logging in separately to each one. Using Zoho Directory as the identity provider, the organization configures OIDC-based single sign-on across all connected applications. Employees sign in once through Zoho Directory and gain immediate access to every application they need, with no additional authentication required.
Partner and customer access management
Organizations can also use OIDC to allow partners or customers to access specific applications using their existing identity provider credentials. With Zoho Directory, businesses can configure OIDC to grant external users secure, controlled access without provisioning separate accounts for each individual.
How Zoho Directory supports OIDC
Zoho Directory acts as the OpenID provider in the OIDC flow, enabling organizations to authenticate users and authorize access to both Zoho and third-party applications securely. Zoho Directory supports OIDC in the following ways.
Acts as a trusted identity provider: Zoho Directory authenticates users and issues identity and access tokens to connected applications, ensuring that user credentials are never shared directly with any application.
Supports multiple application types: Zoho Directory can be configured with a wide range of application types, including server-side web applications, SPAs, and native mobile apps, each using the appropriate OIDC authentication flow.
Issues verified user claims: Upon successful authentication, Zoho Directory shares approved user profile information, such as name, email address, and profile picture, with the relying party through the UserInfo Endpoint.
Provides standard OIDC endpoints: Zoho Directory exposes all necessary OIDC endpoints, including the Authorization Endpoint, Token Endpoint, and UserInfo Endpoint, giving relying parties everything they need to complete the authentication flow securely.
Wrapping up
As organizations manage a growing number of applications and user identities, a reliable and standardized approach to authentication is no longer optional. OIDC addresses this by combining security with simplicity, ensuring that every identity verification is handled through trusted, standards-based mechanisms.
For businesses looking to consolidate identity management, improve user experience, and stay ahead of evolving security demands, adopting OIDC is a meaningful step forward.