What features is System.Text.Json still missing compared to Newtonsoft?

System.Text.Json lacks several Newtonsoft.Json features: no support for DateFormatString customization requiring custom converters instead. Missing built-in handling for DataSet, DataTable, and other legacy .NET types. No automatic $ref/$id reference loop handling—you must use ReferenceHandler.Preserve. Limited support for non-public constructors and properties. No DefaultValueHandling equivalent for conditionally omitting properties. Missing TraceWriter for debugging serialization. No built-in support for F# discriminated unions without custom converters. Cannot serialize/deserialize System.Type directly. Lacks SerializationBinder for type name handling. No ContractResolver equivalent for fine-grained control. However, System.Text.Json provides JsonConverter<T> for custom logic and continuous improvements in each .NET release. Many "missing" features are achievable through custom converters. Use our JSON Editor at jsonconsole.com/json-editor to test compatibility with your data structures. For modern applications, System.Text.Json feature set suffices. Legacy codebases may require Newtonsoft.Json compatibility.