JSON to TypeScript Converter – Free Online Tool
Convert JSON into TypeScript interfaces or type aliases instantly. Free, private, and runs entirely in your browser.
Tool Interface
Convert JSON into TypeScript interfaces or type aliases instantly. Paste your JSON, pick your options, and copy clean, typed definitions — all in your browser.
How it works
- Paste JSON and click Convert — nested objects become their own interfaces.
- Name the root type, choose interface or type-alias style.
- Copy the output straight into your .ts file.
- Arrays of objects infer a shared item type; mixed arrays become unions.
- Empty arrays and nulls fall back to any and null so nothing is mistyped.
100% private — your JSON never leaves your browser.
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About This Tool
JSON to TypeScript Converter – Free Online Tool
Writing TypeScript types by hand from API responses and sample data is slow and error-prone. The JSON to TypeScript Converter by Trencada does it for you: paste any JSON and instantly get clean TypeScript interfaces or type aliases, with nested objects, arrays, and optional properties handled automatically. Everything runs entirely in your browser — your JSON never leaves your device.
How to Convert JSON to TypeScript
- Add your JSON: Paste your JSON into the "JSON input" box, or click "Sample JSON" to fill in a ready-made example.
- Set your options: Name the root type (default "Root"), choose a Style (interface or type alias), pick an Indent (2 or 4 spaces), and toggle "All properties optional" or "Add export keyword" (export is on by default).
- Click "Convert": The tool infers types from your JSON instantly. Tip: pressing Ctrl+Enter inside the input box also converts.
- Copy or download: Click "Copy TypeScript" to copy the output, or "Download .ts" to save it as
types.ts. The stats show how many types were defined and the output size. Click "Reset" to start over.
Key Features
- Generates TypeScript interfaces or type aliases
- Automatic type inference: string, number, boolean, null, and arrays
- Nested objects become their own interfaces
- Arrays of objects infer a shared item type; mixed arrays become unions
- Empty arrays and nulls fall back to
any - Customizable root type name
- Indentation choice: 2 or 4 spaces
- "All properties optional" toggle
- "Add export keyword" toggle
- One-click sample JSON to try the tool instantly
- Copy to clipboard or download as
types.ts - Output stats: types defined and output size
- 100% client-side processing — your JSON never leaves your browser
- Free to use, no account or signup required
Why Choose Trencada?
The JSON to TypeScript Converter is part of Trencada's free Developer & Encoding Tools collection. Every Trencada tool runs directly in your browser: no file uploads, no waiting, no accounts, and no watermarks. Your data stays private on your own device, conversions are instant, and the interface works on desktop and mobile. Whether you are typing API responses, scaffolding a new project, or learning TypeScript, Trencada gives you a fast, private, dependable conversion workflow.
Related Data and Developer Tools
If you work with JSON and APIs, these Trencada tools may also be useful:
- JSON Formatter – Validate and neatly format JSON before converting it.
- JSON to GraphQL Converter – Generate a GraphQL schema from JSON.
- JSON to CSV – Turn JSON into spreadsheet-ready CSV tables.
- YAML to JSON – Convert YAML data into JSON first.
- Timestamp Converter – Decode Unix timestamps found inside JSON data.
- Character Counter – Count characters in your generated output.
- Find & Replace Tool – Bulk-replace values across text.
- Text Case Converter – Fix the letter casing of field names.
Frequently Asked Questions
What does the JSON to TypeScript Converter do?
It reads your JSON structure and generates matching TypeScript type definitions — either interface declarations or type aliases — so you can paste them straight into your project.
What is the difference between interface and type alias style?
Interface style generates interface Root { name: string; }, while type alias style generates type Root = { name: string; };. Both describe the same shape; choose whichever fits your codebase. The "Add export keyword" toggle adds export to each declaration.
How are nested objects handled?
Each nested object becomes its own interface (or type), named after its key with the first letter capitalized — for example, a user object produces a User type.
What happens with arrays?
Arrays of a single type become typed arrays like string[]. Arrays of objects infer a shared item type. Mixed-type arrays become unions such as (string | number)[], and empty arrays fall back to any[].
What does "All properties optional" do?
It adds a ? to every property (e.g. name?: string;), which is useful when your JSON sample may not include every field your data can have.
Is my JSON uploaded to a server?
No. The conversion runs entirely in your browser using JavaScript — your JSON is never sent to Trencada or any third party, and no copy is stored.
What file do I get when I download?
Clicking "Download .ts" saves the generated types as types.ts, ready to drop into any TypeScript project.
Is the JSON to TypeScript Converter free?
Yes. The JSON to TypeScript Converter on Trencada is free to use, with no signup required.