Superjson is a serialization library that safely converts JavaScript expressions to a superset of JSON, extending standard JSON to include Dates, BigInts, Maps, Sets, and other types that the native JSON API cannot handle.
The problem it solves is the friction developers encounter when working with JavaScript objects that fall outside JSON's limited type system. Standard JSON.stringify silently converts or drops these types, forcing manual workarounds. Superjson wraps JSON.stringify and JSON.parse with automatic type preservation, allowing you to serialize complex objects and deserialize them back to their original form without data loss or explicit conversion logic.
Superjson suits any JavaScript project that needs to transmit or store objects with non-JSON-native types. It is particularly valuable in Next.js applications, where getServerSideProps, getInitialProps, and getStaticProps enforce JSON serialization and would otherwise reject Date objects and similar types. The library is framework-agnostic and introduces negligible runtime overhead. For developers choosing between approaches, the README identifies Next.js serialization limitations as a primary use case and mentions an experimental SWC plugin option for Next.js v13 and above, alongside a stable Babel transform for earlier versions.
The project maintains active development with reliable test coverage and continuous integration. The codebase is written in TypeScript, providing type safety and autocompletion for users. The tool has attracted contributions from multiple developers and maintains a public sponsorship model. Development activity shows consistent attention to code quality and framework compatibility, particularly around Next.js integration patterns.
