Generate TypeScript Interface from JSON Online
Overview
Writing TypeScript interfaces by hand from large API responses wastes 20-30 minutes per endpoint. Paste your JSON response and the tool infers types from actual values, generating a ready-to-use interface with proper optional field marking for nullable values.
How to Use This Tool
Paste your JSON object into the input. Click Generate Interface. The tool produces a TypeScript interface with inferred types for every field, including nested object interfaces and array element types.
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PDF Tool →Frequently Asked Questions
How are optional fields detected?
Fields that appear as null in the JSON are marked as optional (field?: type | null). Fields present in the sample are treated as required. You can adjust optionality in the output manually.
Does the tool handle arrays of objects?
Yes. An array of objects generates an interface for the array element type. Multiple items in the array are merged so all observed keys appear in the interface.
Can I use the generated interface directly in my TypeScript project?
Yes. Copy the output and paste it into a .ts or .d.ts file. For complex APIs, review and add JSDoc comments or adjust types (e.g. string to Date) where the tool cannot infer semantic meaning.