About this converter
Build the data classes for your Retrofit / Ktor / kotlinx.serialization layer in seconds. Generated classes use proper null-safety based on what's null in the sample.
Why convert JSON to Kotlin data class
- • Map JSON payloads to Kotlin data classes for Android or backend code.
- • Pair with Moshi or kotlinx.serialization without writing models by hand.
- • Lean on Kotlin null-safety from the very first parse.
How to use
- Paste your JSON on the left panel, or pick one of the sample tabs above.
- The converter infers field names, optionality, and types automatically.
- Copy the generated Kotlin data class on the right and drop it straight into your codebase.
Common pitfalls
- • Inferred types only see the payload you pasted. Add nullable / optional flags for fields that can be missing.
- • Numeric types are inferred as integer or float based on the sample. Real APIs sometimes return both — widen to a number/float type when in doubt.
- • Empty arrays default to an `unknown` element type. Paste a non-empty sample to get a meaningful element type.
FAQ
Is this json to kotlin data class converter free?
Yes. It is fully free, no signup, and runs entirely in your browser. We do not store your input.
Does it work with nested objects and arrays?
Yes. Nested objects produce separate named types, and arrays infer the element type from the first non-null sample.
What about optional / nullable fields?
Fields whose value is null in the sample (or marked optional in JSON Schema / Prisma / GraphQL) are marked optional/nullable in the output. For real APIs, you may want to widen optionality manually after generation.
Can I generate Kotlin Data Class from multiple JSON samples?
Today the tool processes a single sample. For more aggressive inference across multiple shapes, run the converter on the union/merge of your samples or open an issue.
Is the source code available?
Yes — the entire project is open source. See the GitHub link in the footer.