JSON to Kotlin Data Class Converter

JSON to Kotlin Data Class: Core Features and Principles

Still struggling to manually write Kotlin data classes that match JSON API responses? This tool parses your input JSON strings and automatically generates the corresponding Kotlin data class code. JSON (JavaScript Object Notation) is a lightweight data-interchange format, while Kotlin data classes are the core syntax used in the Kotlin language to hold structured data. The core principle of this tool is to analyze JSON key-value pairs and nesting levels, map each JSON object to a data class, convert JSON arrays into List<T> types, and intelligently infer the best Kotlin type for each field (such as String, Int, Boolean, or custom classes).

Why Choose Our JSON to Kotlin Data Class Tool?

• Smart Type Inference: Automatically identifies numbers, booleans, strings, and nulls in JSON to generate accurate nullable and non-nullable Kotlin types like Int? and String.
• Automatic Nested Structure Handling: No manual splitting required. The tool automatically generates independent internal data classes for nested JSON objects and establishes the correct reference relationships.
• Real-time Parsing and Generation: Generates code instantly as you input JSON. No extra clicks needed—what you see is what you get, significantly improving configuration and debugging efficiency.

How to Use

1. Paste or type a complete, properly formatted JSON string into the left input box.
2. Observe the output area on the right, where the tool will display the generated Kotlin data class code in real-time.
3. Verify that the generated class names and property types meet your expectations, then simply select all and copy the code directly into your Kotlin project.

Frequently Asked Questions (FAQ)

Q: Does the JSON to Kotlin converter support Gson or kotlinx.serialization annotations?
A: This tool generates a standard Kotlin data class skeleton. If you need annotations for specific serialization libraries (like @SerialName), you will need to add them manually according to the library's documentation.

Q: What Kotlin property type is generated when a JSON field value is null?
A: The tool infers the field as a nullable type. For example, the name field in the JSON {"name": null} will generate val name: String?.

Important Notes

Please ensure your input JSON format is valid; incorrect formatting will cause parsing to fail. The tool's type inference is based on common patterns. For data with inconsistent formatting (e.g., a field that is sometimes a number and sometimes a string), it may generate a generic type (like Any), which developers will need to adjust manually based on business logic. We recommend renaming the generated default class names (such as Root or Data) according to your actual business context to improve code readability. This tool performs all conversions purely on the frontend—your JSON data is never sent to a server, so you can use it with complete peace of mind.

Technical Notes & Tips

For complex API responses, we recommend using a JSON formatter first to ensure the structure is clear before converting. A typical conversion example is as follows: given the input JSON {"user": {"id": 1, "name": "Alex"}, "tags": ["kotlin", "android"]}, the tool will generate two data classes: a top-level DataClass containing user: User and tags: List<String> properties, and an internal User data class. In Android development, combining these generated data classes with libraries like kotlinx.serialization or Moshi can greatly simplify writing network deserialization code.