JSON to Code Generator — Go, Python, Java, Kotlin, C# & Rust

This is a deterministic source-to-source transformation, not a guess. The JSON is parsed once with JSON.parse following RFC 8259, which defines the six JSON value types — object, array, string, number, boolean, and null. A single recursive pass infers a language-neutral shape for every node, then a per-language emitter prints code using each language's own specification for types and serialization.

1. Primitives. A JSON string maps to string/str/String, and a boolean to the language's bool type. Because JSON has only one number type, the tool checks the literal: a whole number becomes an integer type (int64, i64, long), a decimal becomes a floating type (float64, f64, double). The 64-bit toggle switches integers between 64- and 32-bit width.
2. Objects become named types. Each object is emitted as a struct, record, data class, or class. The name is the PascalCased key — a profile object becomes Profile, and an orders array of objects yields a singularised Order element type. Structurally identical objects reuse one type; genuine name clashes get a numeric suffix.
3. Arrays are merged.Every element is inferred and the schemas are unioned: object fields are merged, and a key present in only some elements is marked optional. A key seen as an integer in one element and a decimal in another widens to the floating type. An empty array has nothing to infer, so its element falls back to the language's any/Value type.
4. Optional and nullable. A missing key is optional; a null value is nullable. Both render as the idiomatic optional form — a pointer with omitempty in Go, Optional[T] = None in Python, Option<T> in Rust, a boxed nullable in Java, and T? in Kotlin and C#.
5. Naming and safety.Field names are cased to each language's convention (exported PascalCase for Go, snake_case for Python and Rust, camelCase for Java and Kotlin), while the original wire name is preserved in a json tag, @JsonProperty, serde rename, @SerialName, or [JsonPropertyName]. Keys that start with a digit or contain hyphens are sanitised (first-name → first_name), and reserved words are escaped.

Because the rules are fixed, identical input and identical options always produce byte-identical output. As a cross-check, the generator runs a structural assignability test — it confirms your original JSON value satisfies the types it just produced — and shows the result as the Accepts input badge. Every mapping is traceable to the language and serializer specifications cited below.

• RFC 8259 — The JavaScript Object Notation (JSON) Data Interchange Format
• The Go Programming Language Specification — Struct types (and encoding/json tags)
• Pydantic v2 — Models and Field aliases
• PEP 557 — Data Classes (field defaults and ordering)
• Serde — Field attributes (#[serde(rename = "...")])
• Microsoft Docs — System.Text.Json and [JsonPropertyName]
• Kotlin — Data classes (with kotlinx.serialization @SerialName)

The type-mapping rules on this page were last cross-checked against the language and serializer specifications above on 2026-07-16. The generator is deterministic, so its output can be reproduced exactly from the same input and options.