jsonparser is a JSON parser for Go that does not require schema definition.
The tool solves the problem of parsing JSON from unpredictable third-party APIs without needing to define structs or use slow generic maps. It works by allowing direct field access through path-based lookup on raw JSON bytes, avoiding the overhead of unmarshaling into intermediate data structures. The parser achieves significant performance gains—up to 6.5 times faster than the standard library's encoding/json package—while allocating no memory during parsing operations.
Developers should choose this tool when working with dynamic or complex JSON payloads where schema definition is impractical or when performance is critical. It suits projects that consume multiple third-party APIs with varying structures, or applications processing large volumes of JSON where memory allocation becomes a bottleneck. The tool offers optional lenient parsing modes for non-standard JSON inputs like single-quoted strings, while maintaining strict RFC 8259 compliance by default. It also provides streaming support through ReaderParser for processing large documents without loading them entirely into memory.
The project has undergone formal verification to L3 assurance level, with every public API traced to formal requirements and tested to 100% Modified Condition/Decision Coverage. The verification process discovered and fixed seven bugs that had escaped years of community use and standard fuzzing, including panic conditions from unchecked dereferences, a silent data-loss bug in the Set operation, and a malformed-output bug in Delete. The tool uses a structure-aware JSON fuzzer capable of generating grammar-valid mutations at high speed, and has executed over 16 million fuzz test cases combining structure-aware, path-mutation, and differential testing approaches.
