Authentication methods are crucial for securing web applications. According to IBM's Cost of a Data Breach Report 2023, stolen credentials account for 20% of incidents and cost an average of $4.5 million. As attack techniques become more sophisticated, implementing strong authentication is no longer optional. Modern authentication requires a layered strategy that goes beyond passwords, with each method having unique strengths from simplicity to advanced protection like biometrics and certificates. The best approach depends on the app's security needs, user workflows, and data sensitivity. Emerging technologies like AI-driven authentication and post-quantum encryption are shaping the future of secure access. Password-based authentication is the most familiar and widely used method for web applications, requiring secure password hashing to avoid vulnerabilities. Multifactor authentication strengthens security by requiring users to pass multiple verification steps, while token-based authentication uses tokens as temporary digital credentials to verify user identity across requests. Biometric authentication uses unique physical characteristics like fingerprints or facial features as identity credentials, offering strong cryptographic identity verification and ideal for service-to-service or machine-to-machine authentication. Single Sign-On (SSO) simplifies access across multiple services while centralizing control, and certificate-based methods deliver high-assurance identity verification for secure enterprise and infrastructure use cases. As threat models grow more sophisticated, the future of authentication is shifting toward smarter, more resilient solutions like AI-powered security and post-quantum encryption.