JSON Format

ServiceStack.Text is an independent, dependency-free serialization library containing ServiceStack's core high-performance utils and text processing functionality, including its premier support for JSON.

Try out ServiceStack.Text Live

A great way to try out ServiceStack.Text is on gist.cafe which lets you immediately run and explore all ServiceStack.Text features from the comfort of your browser with zero software install:

Install ServiceStack.Text

<PackageReference Include="ServiceStack.Text" Version="8.*" />

Simple API

Like most of the interfaces in ServiceStack, the API is simple. Methods that you would commonly use include:

Convenience Serialization Extension Methods

string ToJson(T)
T FromJson()

string ToJsv(T)
T FromJsv()

string ToCsv(T)
T FromCsv()

string ToXml(T)
T FromXml()

Typed JSON

string JsonSerializer.SerializeToString<T>(T value)
void JsonSerializer.SerializeToWriter<T>(T value, TextWriter writer)

T JsonSerializer.DeserializeFromString<T>(string value)
T JsonSerializer.DeserializeFromReader<T>(TextReader reader)

Where T can be any .NET POCO type. That's all there is - the API was intentionally left simple :)

Dynamic JSON parsing API


Supports Dynamic JSON

Although usually used to (de)serialize C#/.NET POCO types, it also includes a flexible API allowing you to deserialize any JSON payload without it's concrete type, see these real-world examples:

Also a thin .NET 4.0 Dynamic JSON wrapper around ServiceStack's JSON library is included in the ServiceStack.Razor project. It provides a dynamic, but more succinct API than the above options.

JS Utils

ServiceStack.Text APIs for deserializing arbitrary JSON requires specifying the Type to deserialize into. An alternative flexible approach to read any arbitrary JavaScript or JSON data structures is to use the high-performance and memory efficient JSON utils in #Script implementation of JavaScript.

JSON.parse("1")       //= int 1 
JSON.parse("1.1")     //= double 1.1
JSON.parse("'a'")     //= string "a"
JSON.parse("{a:1}")   //= new Dictionary<string, object> { {"a", 1 } }
JSON.parse("[{a:1}]") //= new List<object> { new Dictionary<string, object> { { "a", 1 } } }


Since JS Utils is an essential part of #Script it allows for advanced scenarios like implementing a text DSL or scripting language for executing custom logic or business rules you want to be able to change without having to compile or redeploy your App. It uses #Script Context which lets you evaluate the script within a custom scope that defines what functions and arguments it has access to, e.g.:

public class CustomMethods : ScriptMethods
    public string reverse(string text) => new string(text.Reverse().ToArray());

var scope = JS.CreateScope(
         args: new Dictionary<string, object> { { "arg", "value"} }, 
    functions: new CustomMethods());

JS.eval("arg", scope)                                        //= "value"
JS.eval("reverse(arg)", scope)                               //= "eulav"
JS.eval("3.itemsOf(arg.reverse().padRight(8, '_'))", scope) //= ["eulav___", "eulav___", "eulav___"]

//= { a: ["eulav___", "eulav___", "eulav___"] }
JS.eval("{a: 3.itemsOf(arg.reverse().padRight(8, '_')) }", scope)

Install JS Utils

ServiceStack's JS Utils is available in the ServiceStack.Common NuGet package:

<PackageReference Include="ServiceStack.Common" Version="8.*" />

Register JS Utils in ServiceStack.Text

JS Utils is already pre-configured in ServiceStack Web Apps to handle serializing & deserializing object types.

You can also configure to use it in ServiceStack.Text Typed JSON Serializers outside of ServiceStack with:


Pretty Print JSON

You can format JSON into a more readable format with the IndentJson() extension method, e.g:

var prettyJson = dto.ToJson().IndentJson();

ServiceStack's JsonSerializer

ServiceStack's JsonSerializer is optimized for serializing C# POCO types in and out of JSON as fast, compact and cleanly as possible. In most cases C# objects serializes as you would expect them to without added json extensions or serializer-specific artefacts.

JsonSerializer provides a simple API that allows you to serialize any .NET generic or runtime type into a string, TextWriter/TextReader or Stream.

Serialization API

string SerializeToString<T>(T)
void SerializeToWriter<T>(T, TextWriter)
void SerializeToStream<T>(T, Stream)
string SerializeToString(object, Type)
void SerializeToWriter(object, Type, TextWriter)
void SerializeToStream(object, Type, Stream)

Deserialization API

T DeserializeFromString<T>(string)
T DeserializeFromReader<T>(TextReader)
object DeserializeFromString(string, Type)
object DeserializeFromReader(reader, Type)
object DeserializeFromStream(Type, Stream)
T DeserializeFromStream<T>(Stream)

Extension methods

string ToJson<T>(this T)
T FromJson<T>(this string)

Convenient ToJson/FromJson extension methods are also included reducing the amount of code required, e.g:

new []{ 1, 2, 3 }.ToJson()   //= [1,2,3]
"[1,2,3]".FromJson<int[]>()  //= int []{ 1, 2, 3 }

JSON Format

JSON is a lightweight text serialization format with a spec that's so simple that it fits on one page: https://www.json.org.

The only valid values in JSON are:

  • string
  • number
  • object
  • array
  • true
  • false
  • null

Where most allowed values are scalar and the only complex types available are objects and arrays. Although limited, the above set of types make a good fit and can express most programming data structures.

number, true, false types

All C# boolean and numeric data types are stored as-is without quotes.

null type

For the most compact output null values are omitted from the serialized by default. If you want to include null values set the global configuration:

JsConfig.Init(new Config { IncludeNullValues = true });

string type

All other scalar values are stored as strings that are surrounded with double quotes.

C# Structs and Value Types

Because a C# struct is a value type whose public properties are normally just convenience properties around a single scalar value, they are ignored instead the TStruct.ToString() method is used to serialize and either the static TStruct.Parse() method or new TStruct(string) constructor will be used to deserialize the value type if it exists.

array type

Any List, Queue, Stack, Array, Collection, Enumerables including custom enumerable types are stored in exactly the same way as a JavaScript array literal, i.e:


All elements in an array must be of the same type. If a custom type is both an IEnumerable and has properties it will be treated as an array and the extra properties will be ignored.

object type

The JSON object type is the most flexible and is how most complex .NET types are serialized. The JSON object type is a key-value pair JavaScript object literal where the key is always a double-quoted string.

Any IDictionary is serialized into a standard JSON object, i.e:


Which happens to be the same as C# POCO types (inc. Interfaces) with the values:

new MyClass { A=1, B=2, C=3, D=4 }

Only public properties on reference types are serialized with the C# Property Name used for object key and the Property Value as the value. At the moment it is not possible to customize the Property Name.

JsonSerializer also supports serialization of anonymous types in much the same way:

new { A=1, B=2, C=3, D=4 }

Parsing JSON Dates

The default WCF Date that's returned in ServiceStack.Text can be converted with:

function todate (s) { 
    return new Date(parseFloat(/Date\(([^)]+)\)/.exec(s)[1])); 

Which if you're using the servicestack-client npm package can be resolved with:

import { todate } from "servicestack-client";
var date = todate(wcfDateString);

Or if using ss-utils.js that's built into ServiceStack:

var date = $.ss.todate(wcfDateString);

If you change ServiceStack.Text default serialization of Date to either use the ISO8601 date format:

JsConfig.DateHandler = DateHandler.ISO8601;

It can be parsed natively with:

new Date(dateString)

Likewise when configured to return:

JsConfig.DateHandler = DateHandler.UnixTimeMs;

It can also be converted natively with:

new Date(unixTimeMs)

Global Default JSON Configuration

The JSON/JSV and CSV serialization can be customized globally by configuring the JsConfig or type-specific JsConfig<T> static classes with your preferred defaults. Global static configuration can be configured once on Startup using JsConfig.Init(), e.g:

JsConfig.Init(new Config {
    DateHandler = DateHandler.ISO8601,
    AlwaysUseUtc = true,
    TextCase = TextCase.CamelCase,
    ExcludeDefaultValues = true,                

The following is a list of bool options you can use to configure many popular preferences:


DateHandler (dh)


TimeSpanHandler (tsh)


TextCase (tc)


PropertyConvention (pc)


Custom Config Scopes

If you need to use different serialization settings from the global static defaults you can use JsConfig.With() to create a scoped configuration using property initializers:

using (JsConfig.With(new Config { 
    TextCase = TextCase.CamelCase, 
    PropertyConvention = PropertyConvention.Lenient
    return text.FromJson<T>();

Create Custom Scopes using String config

You can also create a custom config scope from a string manually using JsConfig.CreateScope() where you can use the full config name or their aliases, e.g:

using (JsConfig.CreateScope("IncludeNullValues,EDV,dh:ut")) 
    var json = dto.ToJson();

This feature is used to provide a number of different JSON customizations in ServiceStack Services.

Scoped Extension Methods

The convenience serialization methods .ToJson(), .ToJsv(), .ToCsv() also accept a lambda for configuring a custom configuration scope to simplify its usage, e.g:

var json = dto.ToJson(config => config.TextCase = TextCase.SnakeCase);

// Equivalent To:
using var scope = JsConfig.With(new Config { TextCase = TextCase.Default });
var json = response.ToJson();

Type Configuration

If you can't change the definition of a Type (e.g. because its in the BCL), you can specify a custom serialization / deserialization routine to use instead. E.g. here's how you can add support for System.Drawing.Color and customize how Guid and TimeSpan Types are serialized:

JsConfig<System.Drawing.Color>.SerializeFn = c => c.ToString().Replace("Color ","").Replace("[","").Replace("]","");
JsConfig<System.Drawing.Color>.DeSerializeFn = System.Drawing.Color.FromName;

JsConfig<Guid>.SerializeFn = guid => guid.ToString("D");
JsConfig<TimeSpan>.SerializeFn = time => 
    (time.Ticks < 0 ? "-" : "") + time.ToString("hh':'mm':'ss'.'fffffff");

For more advanced custom JSON serializations, see:

Strict Parsing

By default ServiceStack Serializers will try to deserialize as much as possible without error, if you prefer you can opt-in to stricter parsing with:

Env.StrictMode = true;

Where it will instead fail fast and throw Exceptions on deserialization errors.

Custom Serialization

Although JsonSerializer is optimized for serializing .NET POCO types, it still provides some options to change the convention-based serialization routine.

Using Structs to Customize JSON

This makes it possible to customize the serialization routine and provide an even more compact wire format.

E.g. Instead of using a JSON object to represent a point

{ Width=20, Height=10 }

You could use a struct and reduce it to just:


By overriding ToString() and providing a static Size ParseJson() method:

public struct Size
    public double Width { get; set; }
    public double Height { get; set; }

    public override string ToString()
        return Width + "x" + Height;

    public static Size ParseJson(string json)
        var size = json.Split('x');
        return new Size { 
            Width = double.Parse(size[0]), 
            Height = double.Parse(size[1]) 

Which would change it to the more compact JSON output:

    new Size { Width = 20, Height = 10 }.ToJson() // = "20x10"

That allows you to deserialize it back in the same way:

    var size = "20x10".FromJson<Size>(); 

Using Custom IEnumerable class to serialize a JSON array

In addition to using a Struct you can optionally use a custom C# IEnumerable type to provide a strong-typed wrapper around a JSON array:

public class Point : IEnumerable
    double[] points = new double[2];

    public double X 
        get { return points[0]; }
        set { points[0] = value; }

    public double Y
        get { return points[1]; }
        set { points[1] = value; }

    public IEnumerator GetEnumerator()
        foreach (var point in points) 
            yield return point;

Which serializes the Point into a compact JSON array:

    new Point { X = 1, Y = 2 }.ToJson() // = [1,2]

Custom Deserialization

Because the same wire format shared between Dictionaries, POCOs and anonymous types, in most cases what you serialize with one type can be deserialized with another, i.e. an Anonymous type can be deserialized back into a Dictionary<string,string> which can be deserialized into a strong-typed POCO and vice-versa.

Although the JSON Serializer is best optimized for serializing and deserializing .NET types, it's flexible enough to consume 3rd party JSON apis although this generally requires custom de-serialization to convert it into an idiomatic .NET type.


  1. Using JsonObject
  2. Using Generic .NET Collection classes
  3. Using Customized DTO's in the shape of the 3rd party JSON response

CentroidTests is another example that uses the JsonObject to parse a complex custom JSON response.

Late-bound Object and Interface Runtime Types

In order to be able to deserialize late-bound objects like object, interface properties or abstract classes ServiceStack needs to emit type information in the JSON payload. By default it uses __type property name, but can be customized with:

JsConfig.TypeAttr = "$type";

You can also configure what Type Information is emitted with:

JsConfig.TypeWriter = type => type.Name;

Which will just emit the name of the Type (e.g Dog) instead of the full Type Name.

By default ServiceStack will scan all loaded Assemblies to find the Type, but you can tell it to use your own Type Resolver implementation by overriding TypeFinder, e.g:

JsConfig.TypeFinder = typeInfo =>  =>
    var regex = new Regex(@"^(?<type>[^:]+):#(?<namespace>.*)$");
    var match = regex.Match(value);
    var typeName = string.Format("{0}.{1}", match.Groups["namespace"].Value, match.Groups["type"].Value.Replace(".", "+"));
    return MyFindType(typeName);

Runtime Type Whitelist

ServiceStack only allows you to serialize "known safe Types" in late-bound properties which uses a whitelist that's pre-populated with a safe-list of popular Data Types, DTOs and Request DTOs with the default configuration below:

// Allow deserializing types with [Serializable], [DataContract] or [RuntimeSerializable] attributes
JsConfig.AllowRuntimeTypeWithAttributesNamed = new HashSet<string>
    nameof(RuntimeSerializableAttribute), // in ServiceStack.Text
// Allow deserializing types implementing any of the interfaces below
JsConfig.AllowRuntimeTypeWithInterfacesNamed = new HashSet<string>
    "IRuntimeSerializable", // in ServiceStack.Text
    "IVerb",                // IGet, IPost, IPut, IPatch, etc
    "ICrud",                // ICreateDb<T>, IUpdateDb<T>, etc
// Allow object property in ServiceStack.Messaging MQ classes
JsConfig.AllowRuntimeTypeInTypesWithNamespaces = new HashSet<string>

The above rules can be extended to allow your own conventions. If you just need to allow a specific Type you can instead just implement:

JsConfig.AllowRuntimeType = type => type == typeof(MyType);

If you’re in a trusted intranet environment this can also be used to disable the whitelist completely by allowing all Types to be deserialized into object properties with:

JsConfig.AllowRuntimeType = _ => true;

Custom Enum Serialization

You can use [EnumMember] to change what Enum value gets serialized, e.g:

public enum Day
    [EnumMember(Value = "MON")]
    [EnumMember(Value = "TUE")]
    [EnumMember(Value = "WED")]
    [EnumMember(Value = "THU")]
    [EnumMember(Value = "FRI")]
    [EnumMember(Value = "SAT")]
    [EnumMember(Value = "SUN")]

class EnumMemberDto
    public Day Day { get; set; }

var dto = new EnumMemberDto {Day = Day.Sunday};
var json = dto.ToJson();  //= {"Day":"SUN"}

var fromDto = json.FromJson<EnumMemberDto>();
fromDto.Day               //= Day.Sunday