This package is a fork of the RJSONIO package by Duncan Temple Lang. It builds on the same libjson c++ parser, but implements a smarter mapping between JSON data and R classes. This is particularly useful when working with JSON data from pipelines and web APIs. The vignettes describe the behavior in great detail. In addition to drop-in replacements for toJSON and fromJSON, the package contains functions to validate, prettify and minify JSON, and many unit tests to verify that all edge cases are encoded and decoded consistently for use with dynamic data in systems and applications.