This package provides a fast JSON parser, generator and validator which converts JSON', NDJSON (Newline Delimited JSON') and GeoJSON (Geographic JSON') data to/from R objects. The standard R data types are supported (e.g. logical, numeric, integer) with configurable handling of NULL and NA values. Data frames, atomic vectors and lists are all supported as data containers translated to/from JSON'. GeoJSON data is read in as simple features objects. This implementation wraps the yyjson C library which is available from <https://github.com/ibireme/yyjson>.