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Alex Rupérez

Published: 09 Jan 16:23
I starred quicktype/quicktype at GitHub.
Generate types and converters from JSON, Schema, and GraphQL
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quicktype infers types from sample JSON data, then outputs strongly typed models and serializers for working with that data in your desired programming language. In short, quicktype makes it a breeze to work with JSON type-safely. For more explanation, read A first look at quicktype.

Try quicktype in your browser at

Supported Input Languages

  • JSON
  • JSON Schema
  • GraphQL queries

Supported Output Languages

  • C#
  • Go
  • C++
  • Java
  • TypeScript
  • Swift
  • Objective-C
  • Elm
  • JSON Schema
  • Simple Types

Setup, Build, Run

$ npm install
$ npm run build
$ script/quicktype # rebuild and 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 start to watch for changes and recompile and rerun quicktype for live feedback. For example, if you're developing a new renderer for fortran, you could use the following command to rebuild and reinvoke quicktype as you implement your renderer:

$ npm start -- "--lang fortran test/inputs/json/samples/bitcoin-block.json"

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


quicktype has a lot of complicated test dependencies:

  • swift compiler
  • dotnetcore SDK
  • Java, Maven
  • elm tools
  • g++ C++ compiler
  • golang stack

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

$ script/dev
# ... Docker will build the image and start a bash shell
$ npm run test

Test only a specific fixture

$ FIXTURE=golang npm test