The document compares several Scala JSON parsers and their performance when parsing and unparsing JSON documents. It provides details on the parsers, including their implementations, features, and results from benchmark tests. The benchmarks show that Jackson and JAWN are generally the fastest parsers, while parsers using parsing combinators like Twitter Json and the Scala library are much slower. Jackson is also significantly faster than others at unparsing due to its optimized string building. The document provides analysis on reasons for performance differences between parsers.