What is newtonsoft.json?

Json.NET, distributed as the NuGet package Newtonsoft.Json, is a library for working with JSON data in .NET applications. JSON is a widely used text format for exchanging data between programs, such as between a server and a client app. This library gives .NET developers tools to convert objects from their code into JSON text and to parse JSON text back into usable .NET objects. The README for this repository is very sparse. It contains only a short list of links pointing to external resources: the project homepage, documentation site, NuGet package page, release notes, contributing guidelines, and a Stack Overflow tag. No feature descriptions, code examples, or installation instructions appear in the README itself. All of that detail lives in the linked documentation. The repository description calls it a high-performance JSON framework, and with over eleven thousand stars on GitHub and billions of NuGet downloads, it is one of the most widely installed libraries in the .NET ecosystem. It has been a standard choice for JSON handling in .NET projects for many years. Microsoft later introduced a built-in alternative called System.Text.Json in .NET Core 3.0, but Newtonsoft.Json remains in active use across a large number of existing projects. The library is maintained by James Newton-King and is available as open source. For actual usage documentation, the linked homepage and docs site are the right starting points.