quicktypegenerates strongly-typed models and serializers from JSON, JSON Schema, and GraphQL queries, making it a breeze to work with JSON type-safely in any programming language.

Supported Inputs

TypeScriptGraphQL queries

Target Languages

SwiftObjective-CElmJSON SchemaPike

Missing your favorite language? Please implement it!


There are many ways to use quicktype. app.quicktype.iois the most powerful and complete UI. The web app also works offline and doesn't send your sample data over the Internet, so paste away!

For the best CLI, we recommend installing quicktypeglobally via npm:

npm install -g quicktype

Other options:

* limited functionality

Using quicktype

# Run quicktype without arguments for help and options

# quicktype a simple JSON object in C#
echo '{ "name": "David" }' | quicktype -l csharp

# quicktype a top-level array and save as Go source
echo '[1, 2, 3]' | quicktype -o ints.go

# quicktype a sample JSON file in Swift
quicktype person.json -o Person.swift

# A verbose way to do the same thing
quicktype \
  --src person.json \
  --src-lang json \
  --lang swift \
  --top-level Person \
  --out Person.swift

# quicktype a directory of samples as a C++ program
# Suppose ./blockchain is a directory with files:
#   latest-block.json transactions.json marketcap.json
quicktype ./blockchain -o blockchain-api.cpp

# quicktype a live JSON API as a Java program
quicktype https://api.somewhere.com/data -o Data.java

Generating code from JSON schema

The recommended way to use quicktypeis to generate a JSON schema from sample data, review and edit the schema, commit the schema to your project repo, then generate code from the schema as part of your build process:

# First, infer a JSON schema from a sample.
quicktype pokedex.json -l schema -o schema.json

# Review the schema, make changes,
# and commit it to your project repo.

# Finally, generate model code from schema in your
# build process for whatever languages you need:
quicktype -s schema schema.json -o src/ios/models.swift
quicktype -s schema schema.json -o src/android/Models.java
quicktype -s schema schema.json -o src/nodejs/Models.ts

# All of these models will serialize to and from the same
# JSON, so different programs in your stack can communicate
# seamlessly.

Generating code from TypeScript (Experimental)

You can achieve a similar result by writing or generating a TypeScriptfile, then quicktyping it. TypeScript is a typed superset of JavaScript with simple, succinct syntax for defining types:

interface Person {
  name: string;
  nickname?: string; // an optional property
  luckyNumber: number;

You can use TypeScript just like JSON schema was used in the last example:

# First, infer a TypeScript file from a sample (or just write one!)
quicktype pokedex.json -o pokedex.ts --just-types
# Review the TypeScript, make changes, etc.
quicktype pokedex.ts -o src/ios/models.swift

Calling quicktypefrom JavaScript

You can use quicktypeas a JavaScript function within nodeor browsers. First add the quicktype-corepackage:

$ npm install quicktype-core

In general, first you create an InputDatavalue with one or more JSON samples, JSON schemas, TypeScript sources, or other supported input types. Then you call quicktype, passing that InputDatavalue and any options you want.

const {
} = require("quicktype-core");

async function quicktypeJSON(targetLanguage, typeName, jsonString) {
  const jsonInput = jsonInputForTargetLanguage(targetLanguage);

  // We could add multiple samples for the same desired
  // type, or many sources for other types. Here we're
  // just making one type from one piece of sample JSON.
  await jsonInput.addSource({
    name: typeName,
    samples: [jsonString]

  const inputData = new InputData();

  return await quicktype({
    lang: targetLanguage

async function quicktypeJSONSchema(targetLanguage, typeName, jsonSchemaString) {
  const schemaInput = new JSONSchemaInput(new JSONSchemaStore());

  // We could add multiple schemas for multiple types,
  // but here we're just making one type from JSON schema.
  await schemaInput.addSource({ name: typeName, schema: jsonSchemaString });

  const inputData = new InputData();

  return await quicktype({
    lang: targetLanguage

async function main() {
  const { lines: swiftPerson } = await quicktypeJSON(

  const { lines: pythonPerson } = await quicktypeJSONSchema(


The argument to quicktypeis a complex object with many optional properties. Explore its definitionto understand what options are allowed.


quicktypeis Open Sourceand we love contributors! In fact, we have a list of issuesthat are low-priority for us, but for which we'd happily accept contributions. Support for new target languages is also strongly desired. If you'd like to contribute, need help with anything at all, or would just like to talk things over, come join us on Slack.

Setup, Build, Run

quicktypeis implemented in TypeScript and requires nodejsand npmto build and run.

First, install typescriptglobally via npm:

Clone this repo and do:

macOS / Linux

npm install
script/quicktype # rebuild (slow) and run (fast)


npm install --ignore-scripts # Install dependencies
npm install -g typescript # Install typescript globally
tsc --project src/cli # Rebuild
node dist\cli\index.js # Run


Install Visual Studio Code, open this workspace, and install the recommended extensions:

code . # opens in VS Code

Live-reloading for quick feedback

When working on an output language, you'll want to view generated output as you edit. Use npm startto watch for changes and recompile and rerun quicktypefor live feedback. For example, if you're developing a new renderer for fortran, you could use the following command to rebuild and reinvoke quicktypeas you implement your renderer:

npm start -- "--lang fortran pokedex.json"

The command in quotes is passed to quicktype, so you can render local .jsonfiles, URLs, or add other options.


quicktypehas many complex test dependencies:

  • crystalcompiler
  • dotnetcoreSDK
  • Java, Maven
  • elmtools
  • g++C++ compiler
  • golangstack
  • swiftcompiler
  • clangand Objective-C Foundation (must be tested separately on macOS)
  • rusttools
  • pikeinterpreter
  • Bundlerfor Ruby

We've assembled all of these tools in a Docker container that you build and test within:

# Build and attach to Docker container

# Run full test suite
npm run test

# Test a specific language (see test/languages.ts)
FIXTURE=golang npm test

# Test a single sample or directory
FIXTURE=swift npm test -- pokedex.json
FIXTURE=swift npm test -- test/inputs/json/samples





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