Fast interface draft
Turn a realistic JSON sample into copy-ready TypeScript without writing every field manually.
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Generate a TypeScript interface from representative JSON objects, arrays and primitive values, with a configurable root interface name.
JSON to TypeScript converts one representative JSON value into a TypeScript interface. Object properties become typed fields, nested objects become inline object types and arrays receive an item type inferred from the first element.
This is useful for quickly describing API response samples, fixtures and configuration objects. The generator is deterministic and does not call an external AI service, but it can only infer what appears in the sample. It cannot know whether a field is optional, whether several numeric values form a literal union, or whether a null example should also allow another type.
ApiUser.Focused controls, predictable output, and a workflow designed around this exact transformation.
Turn a realistic JSON sample into copy-ready TypeScript without writing every field manually.
Preserve the visible hierarchy as inline object and array types.
Set a meaningful exported interface name for the generated source.
Review the exact cases where one sample cannot describe a complete contract.
Practical details about input, output, privacy, limits, and the best way to use this tool.
No. Every property visible in the sample is generated as required. Add optional markers manually when the API can omit a field.
A non-empty array uses the first item as its item-type example. An empty array becomes unknown[]. Review heterogeneous arrays manually.
A null sample becomes the null type. If the field may also hold another value, change it to a union such as string | null.
No. Nested objects are represented as inline object types inside the root interface.
No. JSON represents those values as strings, so the generator returns string.
No. Core generation is performed with deterministic local rules.
Property names and project conventions vary. Your TypeScript compiler and actual API contract are the final checks.
Objects generate their fields directly. A root array or primitive is wrapped in an interface with a value property.
Learn JSON objects, arrays, value types, validation, formatting, parsing, API workflows, and common syntax errors.
JSON strings map to string; integers and decimals map to number; booleans map to boolean; and null maps to null. Objects become nested property blocks. Arrays use the inferred type of the first item, while empty arrays use unknown[].
A single payload is an observation, not a complete schema. If one response contains a value and another omits it, the generator cannot infer the optional property from the first response. The same limitation applies to nullable fields, mixed arrays and string values that follow a specific format.
The generator normalizes characters that cannot appear in a simple TypeScript identifier. Review keys containing spaces, punctuation, hyphens or leading digits. In some contracts it is better to preserve an unusual JSON key as a quoted property name rather than accept a normalized name.
The input must be valid JSON, including double-quoted property names and strings. Use JSON Validator to diagnose syntax problems and JSON Schema Validator to check an explicit data contract.
A TypeScript interface describes compile-time structure and does not validate untrusted values at runtime. Continue with JSON to Zod Schema for TypeScript runtime validation or JSON to Pydantic Model for Python validation models.
See the TypeScript handbook on object types and RFC 8259 for JSON syntax.