The quicktype command-line interface is the most powerful way to use quicktype. It can process multiple JSON files, fetch data from URLs, and generate a unified set of types for your entire application.

Installation

npm install -g quicktype

Basic Usage

Generate types from a JSON file:

quicktype data.json -o Types.swift

Generate types from a URL:

quicktype https://api.example.com/data -o Types.ts

Multiple Sources

One of quicktype's most powerful features is combining multiple JSON sources into a unified type system:

quicktype user.json posts.json comments.json -o Models.cs

quicktype will analyze all the JSON files and unify common types automatically.

Fetching from APIs

quicktype can fetch JSON directly from APIs:

quicktype \
  "https://api.github.com/users/quicktype" \
  "https://api.github.com/repos/quicktype/quicktype" \
  -o GitHub.swift

Options

Use quicktype --help to see all available options, including:

• --lang - Target language (swift, typescript, csharp, etc.)
• --top-level - Name of the top-level type
• --just-types - Output only type definitions
• --src-lang - Source language (json, schema, graphql)

From JSON Schema

quicktype also supports JSON Schema as input:

quicktype --src-lang schema schema.json -o Types.java

This gives you precise control over the generated types.