JSON to TypeScript Converter

About JSON to TypeScript Converter

The JSON to TypeScript Converter instantly generates strongly-typed TypeScript interfaces from any JSON payload. Whether you are integrating REST APIs, building Angular/React/Vue applications, or scaffolding data models, this tool eliminates manual interface writing and ensures type safety across your TypeScript codebase.

Key Features

• Interface generation — creates TypeScript interfaces with properly inferred types for all JSON values.
• Type alias support — optionally use type aliases instead of interface declarations.
• Optional properties — mark all properties as optional with the ? modifier for flexible typing.
• Export modifier — add export to interfaces for module-based TypeScript projects.
• Nested object handling — recursively generates separate interfaces for nested objects.
• Array type inference — correctly infers array element types including union types for mixed arrays.

How to Use

1. Input JSON — paste JSON into the left editor, upload a file, or fetch from a URL.
2. Configure — set the root interface name and toggle optional props, export, or type alias.
3. Convert — click Convert to TypeScript or press Ctrl+Enter.
4. Export — copy to clipboard or download as a .ts file.

Why Generate TypeScript Types from JSON?

When your application talks to a REST API, the shape of the response is a contract. Without types, a typo in a property name or a wrong assumption about a field only shows up at runtime, often in production. Typed interfaces move those mistakes to compile time, give you autocompletion in your editor, and document the data for the next developer. Writing them by hand for a large payload is tedious, so generating them from a real response is the fastest way to start.

Real-World Use Cases

• Typing responses from a REST or GraphQL endpoint in Angular, React, Vue or Node.js projects.
• Creating models for configuration files, webhooks and message queue payloads.
• Quickly scaffolding data models while prototyping a new feature.
• Typing mock data and test fixtures so tests fail when the real contract changes.
• Migrating a JavaScript codebase to TypeScript one data structure at a time.

Interface or Type Alias?

Both describe object shapes and are interchangeable for most JSON models. Interfaces can be extended and merged, which suits public models that evolve over time. Type aliases can express unions and intersections and are handy for composed types. If your team has a style guide, choose the matching option here; otherwise interfaces are a good default for data transfer objects.

How Types Are Inferred

Strings, numbers and booleans map to string, number and boolean. A null value becomes null, and nested objects produce their own named interfaces so the result stays readable. Arrays of one type become T[], while arrays that mix several types produce union types such as (string | number)[].

Tips for Best Results

• Use a sample that includes optional fields; a property that is absent from the sample will be missing from the interface.
• Mark properties optional when the API may omit them, and use union types where a field can be null.
• Rename the generated root interface to something meaningful such as UserResponse.
• Replace broad string types with literal unions or enums when a field only accepts specific values.

Related Developer Tools

Before generating types, make sure the sample is valid by running it through the JSON Formatter. If you also need runtime validation, create a definition with the JSON Schema Generator, and for back-end models in .NET try the JSON to C# converter. Static types protect you at compile time while schemas protect you at runtime, so many teams use both.