What Is Authentication?

Authentication is the process of verifying a user's identity, confirming that the person trying to access your product is who they claim to be. It is the foundation of any product that has user accounts. Without it, there is no way to associate data with a specific user, restrict access to private information, or maintain persistent sessions.

Common authentication methods include email and password (the traditional approach), magic links (a passwordless method where a login link is sent to the user's email), OAuth (which allows users to sign in with their existing accounts at providers like Google, GitHub, or Apple), and two-factor authentication (which requires a second verification step for added security).

Authentication is one of the areas where implementation quality matters most for security. Common mistakes in auth implementations include storing passwords incorrectly (without proper hashing), poorly handled session tokens, missing CSRF protection, and inadequate rate limiting that allows brute-force attacks. These are vulnerabilities that can cause serious harm if exploited.

For MVP builds, using a well-maintained authentication library or service (rather than building from scratch) is strongly recommended. Libraries like NextAuth.js, or hosted services like Clerk, handle the security-critical parts correctly so teams can focus on the product itself. At Toggle, we always use proven authentication solutions rather than building custom auth, the risk of getting it wrong is too high.