Newtonsoft.json.dll

System.Text.Json is undeniably fast—often 30-50% faster for basic serialization—and uses spans and Utf8JsonReader for zero-copy parsing. However, its initial releases suffered from a lack of features that developers took for granted in Json.NET. It lacked support for ReferenceLoopHandling , PreserveReferencesHandling , polymorphic serialization (without workarounds), dynamic ExpandoObject support, and flexible DateTime parsing. The message from the community was clear: speed is good, but we need our tools.

For existing production systems, Newtonsoft.Json remains a rock-solid foundation. It will continue to work for decades on legacy codebases. For new systems, the choice has become nuanced: choose System.Text.Json for maximum performance, minimal allocations, and Native AOT compatibility; choose Newtonsoft.Json for maximum flexibility, edge-case handling, and a mature, unchanging API surface. newtonsoft.json.dll

Over subsequent releases (.NET 5, 6, 7, and 8), Microsoft has steadily closed the feature gap, adding source generators for Native AOT, polymorphic type discriminators, and improved reference handling. Today, for many greenfield projects, System.Text.Json is a viable, often preferred, default. So, what is the legacy of Newtonsoft.Json.dll ? It is not a cautionary tale of a third-party library being displaced, but a triumphant story of open-source innovation forcing platform-level improvement. James Newton-King did not just write a parser; he wrote a grammar for JSON interaction that was so intuitive it became the standard. Microsoft’s own System.Text.Json API design is, by its own admission, heavily inspired by Json.NET. You see it in the use of JsonSerializerOptions , the JsonConverter base class, and the JsonDocument (which mimics JObject ). System