API samples need types
Paste a REST or GraphQL response and let the JSON to TypeScript Converter create an interface or type alias you can refine in your app.
無料の開発者ツール
JSON から TypeScript 変換 API サンプルから型定義を生成
JSON から TypeScript 変換 turns JSON examples into TypeScript interface or type output for API responses, fixtures, and frontend models while processing locally in your browser.
AD
JSON から TypeScript 変換 Problems
Move from API examples to reliable TypeScript shapes without hand-writing every field.
Arrays rarely stay perfectly uniform
When objects in the same array miss different fields, the JSON to TypeScript Converter marks those properties optional instead of hiding the mismatch.
Developer tools should connect
Format your payload first with JSON Formatter, convert tables with CSV to JSON Converter, or move YAML through YAML JSON Converter before generating types.
JSON から TypeScript 変換 Features
Generate practical TypeScript output from real JSON examples while keeping control over naming and null behavior.
Interface or type output
Switch between interface declarations and type aliases depending on your codebase conventions.
Nested object inference
Objects inside objects and arrays get reusable names so the generated TypeScript stays readable.
Optional fields from arrays
If array items have different keys, missing properties become optional to reflect the observed API shape.
Null union control
Choose whether null should become a union such as string | null or be ignored when other concrete values exist.
Date string detection
ISO-like date strings can become Date types so API timestamps are easy to spot during review.
Local copy and download
Copy TypeScript output or download a .ts file while the JSON never leaves your browser.
How to Use JSON から TypeScript 変換
The workflow is simple: paste JSON, choose generation rules, then copy the TypeScript result.
01
Paste JSON sample data
Add a single object, an array of objects, or nested API response data. Use the sample button to see nulls, dates, arrays, and optional fields.
- Run JSON Formatter first if the payload is hard to read.
02
Choose TypeScript options
Pick interface or type output, toggle export declarations, keep PascalCase type names, and decide how null values and date strings should be handled.
- PascalCase naming affects generated type names, not the original JSON property keys.
03
Review warnings and copy
Check the status area for JSON syntax errors, invalid field names, and inconsistent array structures, then copy or download the generated .ts file.
- Quoted property names are generated when a JSON key is not a valid TypeScript identifier.
JSON から TypeScript 変換 Workflows
Use the JSON to TypeScript Converter for API typing, array schema review, and project-ready export settings.
Turn JSON samples into TypeScript
Paste example API data and create TypeScript declarations that mirror the nested response structure.
Handle inconsistent arrays safely
Detect array objects with different fields and mark missing properties optional so generated types match real data.
Tune output for your codebase
Choose interface or type, export declarations, PascalCase names, date detection, and null union handling before copying.
JSON から TypeScript 変換 Use Cases
Frontend developers, API consumers, and test authors can turn example data into useful TypeScript faster.
API client models
Create response shapes for fetch wrappers, SDK adapters, and frontend data loaders.
Fixture typing
Generate types for mock JSON used in tests, demos, Storybook stories, and seed data.
Migration cleanup
Move JavaScript projects toward TypeScript by starting from the JSON payloads already used in the app.
JSON から TypeScript 変換 FAQ
Common questions about JSON parsing, arrays, optional fields, nulls, dates, and TypeScript output.
Does the JSON to TypeScript Converter upload my data?
No. The JSON is parsed in your browser and the generated TypeScript is created locally.
What happens when array objects have different fields?
The converter merges the observed fields and marks properties missing from some objects as optional.
How are invalid JSON field names handled?
Keys that are not valid TypeScript identifiers are emitted as quoted property names, and the status area shows a warning.
Can I generate both interface and type output?
Yes. Use the mode buttons to switch between interface declarations and type aliases.
Start Using JSON から TypeScript 変換
Paste JSON, generate TypeScript interfaces or types, review optional fields and null unions, then copy the result into your frontend project.
Free forever - browser-only TypeScript generation.