Generate TypeScript types from any JSON payload.
Paste an API response body or configuration object and get ready-to-use TypeScript interfaces or type aliases with modular nested declarations.
export interface Env {
LOG_LEVEL: string;
TIMEOUT_MS: number;
}
export interface Deploy {
service: string;
region: string;
replicas: number;
env: Env;
health: boolean;
notes: null;
}
export interface Root {
deploy: Deploy;
}
# 18 lines · 245 chars
JSONGlow's JSON to TypeScript converter is a free, privacy-first tool that converts raw JSON payloads into clean, reusable TypeScript interfaces and type aliases entirely within your browser.
Compile-Time Type Safety
Transforming runtime JSON into robust TypeScript contracts.
Manually writing TypeScript interfaces for complex API responses, database schemas, and microservice payloads is tedious and error-prone. A single typo in a field name or an incorrect property type can lead to subtle bugs across your application stack.
JSONGlow's JSON to TypeScript converter automatically parses the structure of your JSON data, infers primitive and nested types, and generates clean, modular TypeScript code that follows modern best practices. If you also need runtime data validation, generate schemas with our JSON to Zod Converter or format payloads beforehand using the JSON Formatter.
Rather than emitting messy inline nested types, JSONGlow extracts every sub-object into its own named, exported interface or type alias using idiomatic PascalCase. Array fields are thoroughly analyzed to detect uniform versus union types, ensuring your codebase benefits from precise type inference.
Whether you need standard `interface` declarations for extensible object structures or `type` aliases for flexible unions, toggle between modes with one click. Everything runs locally in your browser with zero latency and zero data exposure. You can also validate contracts against JSON Schema with the JSON Schema Validator or inspect raw syntax with our JSON Validator.
Workflow Guide
How to generate TypeScript types in 3 simple steps
Input sample payload
Paste your API response, database document, or configuration JSON into the left editor pane.
Interface vs. Type alias
Use the toolbar toggle to choose between exported 'interface' declarations or 'type' aliases.
Integrate into your codebase
Click 'Copy' to paste types directly into your IDE, or click 'Download' to save the `.ts` file locally.
Practical Demonstration
JSON to TypeScript Conversion Example
See how a nested JSON payload is transformed into modular, strongly-typed TypeScript interfaces.
{
"server_name": "api-gateway-01",
"port": 443,
"ssl_enabled": true,
"cluster": {
"region": "us-east-1",
"zone": "us-east-1a",
"instances": 5
},
"tags": ["production", "edge", "gateway"],
"metadata": null
}export interface Cluster {
region: string;
zone: string;
instances: number;
}
export interface Root {
server_name: string;
port: number;
ssl_enabled: boolean;
cluster: Cluster;
tags: string[];
metadata: null | unknown;
}Typing Pitfalls & Edge Cases
Common TypeScript typing challenges
Using 'any' instead of precise union types
Why it happens: Naive converters map mixed arrays or nullable fields to `any`, breaking TypeScript's type safety.
Monolithic inlined object types
Why it happens: Generating giant inline types (`cluster: { region: string; zone: string; ... }`) makes types unexportable and difficult to reuse.
Interfaces vs. Type Aliases for unions
Why it happens: TypeScript interfaces cannot declare union types directly (e.g. `interface ID = string | number` is illegal).
Core Capabilities
Built for production TypeScript development
Interface & Type Toggle
Switch effortlessly between exported TypeScript interfaces and type aliases.
Modular Nested Extraction
Deep object structures become clean, reusable PascalCase declarations instead of monolithic blobs.
Union-Aware Array Typing
Mixed arrays collapse to precise union types like `(string | number)[]` instead of `any[]`.
Deterministic Formatting
Emits consistently indented, lint-clean TypeScript code ready to paste into `.ts` or `.tsx` files.
One-Click Copy & Download
Instantly copy to clipboard or download the generated TypeScript definitions as a `.ts` file.
100% Client-Side Privacy
No server uploads. Safe for proprietary tokens, customer records, and internal schemas.
Frequently Asked Questions
Common questions answered.
Need more help? Our tools execute entirely in your browser without transmitting any payload to remote servers.
Should I choose 'interface' or 'type' alias for my TypeScript code?+
Both representations are generated from the same JSON data. Interfaces support declaration merging and extends patterns, making them ideal for object-oriented architectures and public libraries. Type aliases are more flexible for unions, intersections, and primitive aliases. You can switch between them with one click.
How does the converter handle deeply nested JSON objects?+
Every nested sub-object is extracted into its own independently named and exported TypeScript interface or type alias. Names are automatically derived from property keys using PascalCase conventions.
How are heterogeneous arrays typed?+
The converter scans every element within an array. If elements share the same type, a simple array type like `string[]` or `User[]` is produced. If elements vary, a union type like `(string | number | boolean)[]` is created.
How are null or empty array fields handled?+
Fields with `null` values are typed as `null | unknown` or optional properties, while empty arrays default to `unknown[]` to alert developers to provide specific generics.
Is my JSON data uploaded anywhere when generating TypeScript types?+
No. All TypeScript generation runs 100% in your browser using local AST parsing. No network calls are made with your data.
Explore More Tools & Guides
The JSONGlow developer kit.
JSON to Zod Schema
Generate production-grade Zod validation schemas & TypeScript types with one-click .ts download.
YAML ↔ JSON
Bi-directional YAML 1.2 converter for K8s manifests, Docker Compose, and GitHub Actions.
JSON Formatter
Format, beautify, indent, sort keys alphabetically, and inspect nested JSON structures.