bcryptjs and argon2 are two leading password hashing libraries for JavaScript authentication systems. bcryptjs is a pure JavaScript implementation of bcrypt, offering CPU-intensive password hashing with a simple API and zero native dependencies. argon2 is the Node.js binding for Argon2, the modern memory-hard hashing algorithm that won the Password Hashing Competition and is recommended by OWASP and NIST for new applications.
This comparison matters because choosing the right hashing algorithm directly impacts your application's security posture and deployment constraints. bcryptjs targets developers prioritizing portability, simplicity, and compatibility across edge runtimes and browsers, while argon2 serves teams building high-security server applications where GPU resistance and configurable memory-hardness are critical. Both are production-ready, but they make fundamentally different trade-offs between accessibility and advanced security features.
For new server-side JavaScript projects, argon2 is the clear winner if your deployment environment supports native modules and you have adequate RAM. Its superior resistance to GPU attacks and industry endorsements from OWASP and NIST make it the responsible choice for applications handling sensitive user data, financial information, or facing sophisticated attackers. The configuration complexity is a one-time learning investment that pays security dividends for years.
bcryptjs remains the pragmatic choice for three specific scenarios: deploying to edge runtimes or serverless platforms without native module support, maintaining legacy codebases where migration risk outweighs security gains, or building applications with severe memory constraints. If your threat model doesn't include well-funded attackers with GPU farms, bcryptjs provides adequate security with significantly simpler deployment. However, starting a greenfield authentication system with bcryptjs in 2025 means accepting technical debt from day one—only choose it when deployment constraints force your hand.