MSAL Explained: Everything You Need to Know

Modern applications need secure, scalable authentication without adding unnecessary complexity. Microsoft Authentication Library (MSAL) simplifies identity management and also helps to ensure compliance. The library enables apps to securely authenticate users through Azure Active Directory and Microsoft identity platforms.

It abstracts complex OAuth and OpenID Connect flows, allowing skilled developers to smoothly implement enterprise-grade authentication. In this guide, we’ll explore MSAL and how it works.

What is MSAL?

MSAL simplifies how applications authenticate users and obtain access tokens securely. It manages sign-in flows, token lifecycle, and single sign-on across sessions and platforms. The MSAL library comes with built-in support for modern authentication standards such as OpenID Connect and JSON Web Tokens (JWT). This helps to reduce implementation effort and ensure strong security. Overall, MSAL authentication enables developers to deliver reliable, secure experiences in a hassle-free way.

Applications Supported by MSAL

Microsoft Authentication Library (MSAL) is designed to support authentication across a wide range of modern application types. When building complex or AI-powered apps, developers can use MSAL Python, which is the official Microsoft Authentication Library for Python.

Developers can use the Microsoft MSAL library for handling the authentication mechanism in the following types of applications:

• Web Apps
• Web APIs
• Single Page Applications (SPAs)
• Mobile & Native Applications
• Daemon & Server-Side Applications

Advantages of Using MSAL Library

Adopting Microsoft MSAL allows development teams to shift their focus from managing complex security logic to building meaningful application features. MSAL abstracts authentication workflows and token management.

The key benefits of using MSAL are:

• Allows developers to focus on core application functionality instead of complex security implementation.
• Enables robust authentication with minimal custom code and faster integration.
• Stays aligned with the latest security standards through continuous updates from Microsoft.
• Supports multiple authentication methods to suit different application scenarios.
• Reduces long-term maintenance while maintaining enterprise-level security, even for teams without deep security expertise.

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Disadvantages of Using MSAL

• Not suitable for complex microservices environments with decentralised identity requirements.
• Developers must have a clear understanding of authentication sources and identity flows.
• Focuses primarily on authentication and token issuance rather than fine-grained authorisation logic.
• It does not manage role-based or feature-level access control within the application itself.

How Does MSAL Work?

You add the MSAL library to your application and configure it with your app’s details registered in Azure AD (Microsoft Entra ID). Further, the library works in the following way.

• MSAL initiates the sign-in process when a user attempts to access a protected resource. It often redirects the user to Microsoft’s secure sign-in page for authentication.
• The mechanism requests security tokens after gaining successful authentication and user consent (if required). These include access tokens, ID tokens, and refresh tokens for the requested APIs and scopes.
• It securely stores the issued tokens and manages their lifecycle. It automatically refreshes tokens before they expire by using the refresh token.
• The application uses the cached access token to call protected web APIs, such as Microsoft Graph. This token proves the user’s identity and permissions.
• MSAL provides a consistent API across platforms. It abstracts underlying OAuth 2.0 and OpenID Connect flows, including Authorization Code Flow with PKCE for SPAs.

Best Practices for Using MSAL Effectively

It is important to plan authentication as part of your application’s core architecture. You must start by clearly defining your authentication and access requirements.

So, you can select the most appropriate MSAL flow and sign-in method. Working closely with IT or identity teams helps ensure claims and scopes. It also ensures that token configurations are managed correctly, especially when custom behaviour is needed beyond MSAL’s default capabilities.

Conclusion

Security experts consistently recommend delegating authentication and identity management to well-maintained libraries. Using established authentication libraries significantly reduces the amount of security-critical code developers need to manage. This lowers the risk of misconfigurations and vulnerabilities.