What types of authentication for web applications do you know?

Main types of authentication for web applications:

• Basic Authentication — transmitting login and password in HTTP headers (usually over HTTPS).
• Form-based Authentication — user enters data into a form, the server verifies and establishes a session.
• Token-based Authentication (e.g., JWT) — after login, the user receives a token that is sent with each request.
• OAuth / OAuth2 — an authorization protocol that allows using third-party service credentials.
• SAML — used for Single Sign-On (SSO) in corporate systems.
• Multi-factor Authentication (MFA) — requires a second factor (SMS, app-generated codes) in addition to the password.

The choice depends on security requirements and application architecture.