$ Turn JSON into typed definitions
Paste JSON and generate TypeScript interfaces or Go structs in one step.
JSON Input
Paste a JSON payload and generate typed definitions.
Generated Output
Interfaces ready to copy.
export interface Profile {
displayName: string;
signupAt: string;
}
export interface RootPayload {
id: number;
email: string;
isActive: boolean;
roles: string[];
profile: Profile;
}Why this tool exists
Vultio Type Generator is built for the moment when you have a real JSON payload but no typed model yet. That happens constantly with third-party APIs, internal services that move fast, sample webhook bodies, or backend responses that are only documented with examples.
Instead of translating fields one by one into interfaces or structs, you can paste representative JSON and generate a first typed draft for TypeScript, Go, or Java. That speeds up exploration and removes the boring mechanical work from the early integration phase.
The important nuance is that generated types are a starting point, not the final design. They help you bootstrap models quickly, then refine naming, nullability, optionals, and domain intent once you understand the contract better.
That makes type generation particularly valuable during the messy middle of integration work: the moment after you finally have a payload example, but before you want to spend time hand-authoring every nested object and array shape.
Common use cases
Example input / output
JSON to TypeScript
JSON to Go struct
Nested payload expansion
Common errors
cause:The payload is not valid JSON because of syntax mistakes such as trailing commas, malformed braces, comments, or single quotes.
fix:Validate and format the JSON first, then retry generation with a clean payload.
cause:The sample payload does not represent all real-world field variants, so the generated structure reflects only what was observed in that example.
fix:Use a representative payload that includes optional fields, nested objects, and typical array content before trusting the generated types.
cause:Automatic inference cannot guess business meaning, naming conventions, union semantics, or whether a field should be optional across the broader API surface.
fix:Treat the output as scaffolding, then refactor names, optionality, enums, and shared reusable types manually.
cause:Type generation infers structure from a sample; it does not guarantee that future payload variants, nullable fields, or undocumented branches will follow the same pattern.
fix:Combine generated types with runtime validation, broader sample coverage, or schema review before trusting them as the whole contract.
How developers use it in practice
A tiny example is fast, but it often hides nullable fields, nested objects, and real array item shape. Use a payload that reflects the contract you actually expect in code.
Generated types help you move faster, but they are strongest when checked against a JSON Schema, OpenAPI spec, or known documentation so you do not silently encode accidental sample-only structure.
The best use of a generator is to skip the boring first draft. Before shipping, promote repeated nested types, rename weak fields, and decide where optionals or domain-specific types belong.
If a provider adds nested fields or changes array item shape, regenerate from the newer representative payload and compare the diff. It is usually faster and safer than manually patching a stale generated model.
When not to use this tool
Limits and implementation notes
If the sample omits optional fields or variant shapes, the generated types cannot invent them. Garbage sample in, misleading model out.
Automatic generation is good at obvious primitives and nesting, but broader API evolution often needs manual modeling for nullable fields, enums, and multiple response variants.
The output is meant to accelerate setup, not replace thoughtful model design, validation, serialization rules, or domain naming cleanup.
For mature integrations, you often need multiple payload examples or supporting docs to model optional branches, polymorphic items, or versioned responses well.
Related guides
Standards & references
Related tools
Frequently asked questions
What does JSON to TypeScript online conversion produce?
It converts JSON into TypeScript interfaces with correct types inferred from your data — string, number, boolean, arrays, and nested objects are all handled automatically.
Which languages does Type Generator support?
Type Generator supports TypeScript interfaces, Go structs, and Java classes. Select the target language before converting your JSON.
Does it handle nested JSON objects?
Yes. Nested objects are recursively converted into separate interface or struct definitions, keeping the output clean and idiomatic for each language.
Can I use it for API response mapping?
Yes. Paste a real API response and get a typed model immediately. It is especially useful when integrating a third-party API without an SDK.
Is my JSON sent to a server?
No. Type generation runs entirely in your browser. Your JSON payload is never uploaded anywhere.