Early when JSON was new, people were using the JavaScript parser included in .NET to get the values. Then Microsoft build a small JSON parser for their ASP.NET

Early when JSON was new, people were using the JavaScript parser included in .NET to get the values. Then Microsoft build a small JSON parser for their ASP.NET library. But then James Newton-King build JSON.NET and Microsoft eventually switched a lot of their libraries over to it because it was just very good. It could do a lot of stuff very fast with a nice API. Last year Microsoft introduced a new and more efficient way to allocate memory natively into .NET Core 2.0 (Span<T>). Since JSON.NET is still used by .NET Framework that doesn't support the new API, Microsoft created System.Text.Json that includes a new JSON parser that utilizes it. The first Microsoft project to use the new parser by default was ASP.NET Core 3.0.