JSON to C# Classes

How to use it

1. Paste a JSON response body or drop a .json file — the C# regenerates as you edit.
2. One payload rarely shows every field: add another sample from the same endpoint and the shapes merge.
3. Set the serializer first — it decides every attribute — then classes or records, nullable reference types, List<T> or T[], and the top-level type name.
4. Copy the source, download it as a .cs file, or share a link that reopens these samples and options.

Paste sample JSON and read back compilable C#: one type per object shape, attributes pinning the exact wire keys, collections as List<T> or arrays. Feed several payloads from the same endpoint and any field missing somewhere turns nullable. Output targets System.Text.Json or Newtonsoft.Json, classes or records, nullable reference types on or off — and generation happens in this tab, with nothing posted anywhere.

Examples

{"first_name": "Ana"}

namespace QuickType
{
    using System;
    using System.Collections.Generic;

    using System.Text.Json;
    using System.Text.Json.Serialization;
    using System.Globalization;

    public partial class Root
    {
        [JsonPropertyName("first_name")]
        public string FirstName { get; set; }
    }
}

{"user_id": 7, "is_admin": false}

namespace QuickType
{
    using System;
    using System.Collections.Generic;

    using System.Globalization;
    using Newtonsoft.Json;
    using Newtonsoft.Json.Converters;

    public partial class Root
    {
        [JsonProperty("user_id")]
        public long UserId { get; set; }

        [JsonProperty("is_admin")]
        public bool IsAdmin { get; set; }
    }
}

{"first_name": "Ana"}

{"first_name": "Maya", "middle_name": "Rose"}

namespace QuickType
{
    using System;
    using System.Collections.Generic;

    using System.Text.Json;
    using System.Text.Json.Serialization;
    using System.Globalization;

    public partial class Root
    {
        [JsonPropertyName("first_name")]
        public string FirstName { get; set; }

        [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
        [JsonPropertyName("middle_name")]
        public string? MiddleName { get; set; }
    }
}

{"$type": "user", "name": "Ana"}

namespace QuickType
{
    using System;
    using System.Collections.Generic;

    using System.Text.Json;
    using System.Text.Json.Serialization;
    using System.Globalization;

    public partial class Root
    {
        [JsonPropertyName("$type")]
        public string Type { get; set; }

        [JsonPropertyName("name")]
        public string Name { get; set; }
    }
}

Every example on this page is executed against the same engine that powers the tool, on every build.

Common errors

Unexpected '}' at line 1, column 16 — probable cause: trailing comma after the last property.

Generation only starts from strict JSON, and the diagnostic points at the failing character with a caret frame. Trailing commas are legal in C# initializers and modern JavaScript, which is how they sneak into hand-edited payloads — delete the comma and the classes appear.

Sample 2 of 3 is not valid JSON — fix or remove it.

Merging needs every sample to parse on its own. The banner names the failing tab, and the diagnostics above it carry line, column and probable cause — correct that sample or drop its tab and generation resumes.

Input is larger than the 10 MB limit for this tool.

Past the cap the whole paste is declined — nothing is silently trimmed to fit. Keep a handful of representative records instead, or run the quicktype command shown on this page over the complete file.

Keyboard shortcuts

⌘/Ctrl + Enter

Regenerate the C# immediately, at any input size.

⌘/Ctrl + S

Save the generated source as a .cs file (overrides the browser save-page dialog; the help overlay notes this).

⌘/Ctrl + C

With nothing selected, copy the entire generated source; an active selection copies normally.

⌘/Ctrl + Shift + C

Force-copy the entire source even while a selection exists.

t

Cycle the color theme (idle in text fields and during IME composition).

? or ⌘/Ctrl + /

Open the keyboard help dialog listing these bindings.

Esc

Close the topmost dialog; your samples stay put.