C# to JSON Converter
Paste C# classes or objects. Get clean JSON back.
What this tool does
If you have ever had to hand-craft a JSON payload that mirrors a C# class — for a test, an API call, or some documentation — you know how tedious it gets. Paste the C# here and you get back valid JSON without manually rewriting anything. It handles a single object initializer, a whole model file with several classes, or something deeply nested — same result: a complete JSON document with every field preserved.
It is not just string-replacement. The converter knows how C# actually serializes at runtime: decimal suffixes like 49.99m drop the m and become JSON numbers, DateTime and DateTimeOffset come out as ISO-8601 strings per RFC 8259, Guid becomes a standard hex string, nullables with null values become null, and collections follow what System.Text.Json and Newtonsoft.Json would produce — List<T> and arrays as JSON arrays, Dictionary<K,V> as a JSON object.
Serialization attributes are respected too. [JsonPropertyName("x")] renames the key, [JsonIgnore] drops the property. If you paste several classes at once, each one comes out as a top-level entry in the JSON, with nested types expanded and inherited properties from base classes rolled in. Nothing gets silently lost.
How to use it
Three steps. Works the same whether you paste five lines or a full model file.
Paste your C# (or try the sample)
Drop your C# into the left editor as-is. An object initializer, a full class definition, multiple classes, or nested structures — all fine. Click Load Sample if you want to see a realistic example first.
You do not need to clean up the code — leave the C# syntax, access modifiers, and attributes as they are. Just paste.
Hit Convert
Click the green Convert button. The tool reads the C#, preserves every class and property, and builds the JSON in one pass. You will see a short loading indicator while it runs.
Copy the JSON
The right panel fills with indented, MDN-compatible JSON. Copy it straight into your API request, test fixture, config file, or documentation.
When this actually comes in handy
Building API fixtures
You have a C# request model and need a JSON payload to drop into Postman or curl. Paste the class, get the JSON, move on.
Starting config files
A Settings class with 40 properties turns into a ready-to-edit JSON template for appsettings.json or any config store — no handwritten boilerplate.
Keeping docs in sync
Generate JSON examples for a README, API reference, or OpenAPI spec straight from your actual models, so the docs match the code.
Seeding test data
Turn object initializers from your unit tests into JSON seed files for integration tests, mock servers, or database fixtures.
Common questions
Can I paste multiple classes at once?
Yes — paste a whole file. Each top-level class comes out as its own key in the JSON, with nested types expanded and inherited properties from base classes included. Nothing is dropped.
Does it honour attributes like [JsonPropertyName] or [JsonIgnore]?
Yes. [JsonPropertyName("x")] and [JsonProperty("x")] rename the JSON key, and [JsonIgnore] removes the property from the output — the same behaviour you would get from System.Text.Json.
How does it handle decimal, DateTime, Guid, and the usual C# types?
Decimals (49.99m) lose the suffix and become JSON numbers. DateTime and DateTimeOffset come out as ISO-8601 strings. Guid is a standard 8-4-4-4-12 hex string. TimeSpan becomes a duration string. Nullables with a null value become JSON null; otherwise the underlying type is serialized.
What about nested classes, lists, and dictionaries?
List<T>, arrays, HashSet<T>, and IEnumerable<T> all become JSON arrays. Dictionary<K,V> becomes a JSON object. Nested object initializers — an Address inside an Order, for example — are expanded as nested JSON objects with every field intact.
Is my code stored?
Your code is sent to the backend for conversion and is not persisted — we do not log the payload. As always with online tools, if the code is genuinely sensitive, give it a look before pasting.
What if the C# has something unusual — methods, delegates, IntPtr?
Those get emitted as null rather than failing the whole conversion, so the rest of your model still comes through. If the code itself has syntax errors, fix the obvious ones first — the parser is forgiving but not magic.
Other tools you may need
C# to JSON is one piece of the puzzle. Here are the tools that pair well with it: