goccy/go-json

go-json is a Go library for converting data to and from JSON format. It is designed as a drop-in replacement for the standard library's built-in encoding/json package, meaning you can switch to it by changing a single import line and the rest of your code stays the same. The main reason to use it over the standard library is speed. The README includes benchmark charts showing it is faster than several comparable Go JSON libraries for both encoding (converting Go data to JSON text) and decoding (converting JSON text back into Go data). It achieves this through a set of internal optimizations: reusing memory buffers across calls rather than allocating new ones each time, pre-building type-specific processing functions to avoid slow reflection at runtime, and generating optimized code paths at program startup rather than inspecting types on every call. Beyond raw speed, the library adds a few features not found in the standard package. You can pass a context value through to custom marshal and unmarshal methods (useful for things like tracing or cancellation). You can dynamically filter which fields of a struct get included in JSON output without losing type safety. Encoded output can also be syntax-colored for display purposes. Installation is one line using the standard Go module tool. Switching an existing project over requires only updating the import path. The library maintains full compatibility with the standard encoding/json interface, which several other faster JSON libraries sacrifice in exchange for their speed gains. The README notes a fuzzing test repository exists to help catch edge cases and bugs.