Single Sign On
Single Sign On (SSO) is an authentication method that allows a user to log in with a single set of credentials across multiple independent software systems. In other words, the user can log in to a whole bunch of accounts, by logging in to a single account.
Instead of remembering separate usernames and passwords for each and every application, users authenticate once through a central identity provider (IdP), which then grants access to all connected service providers (SPs), without requiring additional logins.
The table below will give you an indication of which identity providers (like Facebook, Google and Microsoft) can be used to log in to which service providers.
| Service Provider | Microsoft | ||
|---|---|---|---|
| Asana | ✓ | ✓ | |
| Box | ✓ | ||
| Figma | ✓ | ||
| GitLab | ✓ | ||
| IMDb | ✓ | ||
| ✓ | ✓ | ✓ | |
| Medium | ✓ | ||
| ✓ | ✓ | ||
| ServiceNow | ✓ | ||
| Slack | ✓ | ✓ | |
| SoundCloud | ✓ | ||
| Spotify | ✓ | ||
| Stack Overflow | ✓ | ||
| Trello | ✓ | ✓ | |
| Yelp | ✓ | ||
| Zoom | ✓ | ✓ | ✓ |
How SSO Works
The SSO authentication flow typically involves three parties: the user, the service provider (the application the user wants to access), and the identity provider (the central authentication service). When a user attempts to access a service provider for the first time, they are redirected to the identity provider's login page. After successful authentication, the identity provider issues a token (such as a SAML assertion, OAuth access token, or OpenID Connect ID token) that the service provider validates to grant access.
Subsequent attempts to access other connected service providers reuse the existing session with the identity provider, eliminating the need to re-enter credentials. This is why it is called "single" sign-on.
Benefits of SSO
SSO offers several advantages for both users and organisations. Users benefit from reduced password fatigue, as they only need to remember one set of credentials. This leads to fewer password reset requests and improved productivity.
For organisations, SSO centralises user management, making it easier to provision and deprovision access across all connected systems. When an employee leaves the company, disabling their SSO account immediately revokes access to all integrated applications. SSO also simplifies compliance with auditing requirements by providing a central authentication log.
Common SSO Protocols
SAML (Security Assertion Markup Language)
SAML is an XML-based standard used primarily for enterprise SSO. It enables identity providers to pass authentication and authorisation data to service providers via SAML assertions. SAML is widely used in enterprise environments and is supported by major platforms such as Microsoft Entra ID, Okta, and Google Workspace.
OAuth 2.0
OAuth 2.0 is an authorisation framework that allows applications to obtain limited access to user accounts on an HTTP service. While OAuth 2.0 is primarily an authorisation protocol, it is often used in conjunction with OpenID Connect to provide authentication. OAuth 2.0 is the foundation for many social login implementations, including "Sign in with Google" and "Sign in with Facebook".
OpenID Connect (OIDC)
OpenID Connect is an authentication layer built on top of OAuth 2.0. It adds an ID token (a JSON Web Token or JWT) that contains verified identity information about the user. OIDC is the modern standard for SSO on the web and is widely adopted by contemporary platforms.
Security Considerations
While SSO improves user experience and centralises access control, it also introduces a single point of failure. If an attacker compromises the identity provider, they gain access to all connected applications. Therefore, SSO should always be combined with multi-factor authentication (MFA) to add an extra layer of security.
Organisations should also implement Conditional Access policies that evaluate sign-in risk, device compliance, and geographic location before granting access. Regular monitoring of SSO authentication logs can help detect suspicious activity, such as impossible travel scenarios or unusual login times.
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References
Cyber Writes Team. (2026, January 14). 11 Best Single Sign-On (SSO) solutions & providers – 2026. Cyber Security News. https://cybersecuritynews.com/single-sign-on-solutions/
Wikipedia. (n.d.). Single sign-on. In Wikipedia. https://en.wikipedia.org/wiki/Single_sign-on
For more information, please visit the official Wikipedia page on single sign-on; or run a search via Bing, DuckDuckGo or Google for “single sign on”.
📅 June 18, 2026
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