How to generate models from a GraphQL schema with Quicktype?

Quicktype supports GraphQL queries as input: use the CLI or web app to paste a GraphQL introspection query or schema, and it will output type-safe models in your chosen language, ensuring alignment with your API.

Quicktype vs manual code generation: which is better for large teams?

Quicktype automates consistency across languages, reducing human error, but manual generation allows more control over optimizations. For large teams with multi-language stacks, Quicktype saves time on boilerplate but may require schema discipline.

Can Quicktype handle JSON with optional or nullable fields?

Yes, Quicktype infers optional types from samples (e.g., missing properties) and allows editing in JSON Schema or TypeScript first. It generates proper nullable/optional annotations in target languages like Swift optionals or TypeScript unions.

How to integrate Quicktype into a CI/CD pipeline for Android projects?

Install Quicktype via npm in your build environment, commit a JSON Schema file, and add a script step to run quicktype, generating Kotlin or Java models before compilation, ensuring models stay synced with API changes.

Is Quicktype good for generating React PropTypes from JSON?

Yes, Quicktype lists Prop-Types as a target language, allowing you to generate React prop validation code from JSON samples or schemas, though for TypeScript projects, direct TypeScript output might be preferable.

Quicktype or OpenAPI generators: what's the difference?

Quicktype is more flexible with input formats (JSON, GraphQL) and supports more languages, while OpenAPI tools are specialized for REST APIs. Choose Quicktype for diverse data sources or multi-language needs beyond OpenAPI specs.

Open-Awesome

quicktype

Apache-2.0TypeScript

Generate strongly-typed models and serializers from JSON, JSON Schema, TypeScript, and GraphQL for many programming languages.

Visit Website GitHub

13.8k stars1.2k forks0 contributors

What is quicktype?

Quicktype is a developer tool that automatically generates strongly-typed data models and serialization code from JSON, JSON Schema, TypeScript, or GraphQL definitions. It solves the problem of manually writing repetitive, error-prone model classes to safely parse and serialize JSON data across different programming languages.

Target Audience

Developers and teams working in multi-language stacks (e.g., mobile, web, backend) who need consistent, type-safe data models, or anyone tired of writing boilerplate serialization code.

Value Proposition

It dramatically speeds up development by generating correct, production-ready models from sample data or schemas, ensures consistency across different parts of a system, and integrates easily into build processes and existing codebases via CLI, library, or web app.

Overview

Generate types and converters from JSON, Schema, and GraphQL

Use Cases

Best For

Generating type-safe API client models from a live JSON API endpoint
Creating consistent data models in Swift, Kotlin, and TypeScript from a single JSON Schema
Quickly prototyping with structured data by converting JSON samples into classes in your language of choice
Ensuring type safety when working with JSON in languages like Python or JavaScript
Building a multi-platform application where the same data structures are used on iOS, Android, and backend
Automating model generation as part of a CI/CD pipeline from committed schema files

Not Ideal For

Projects with highly dynamic or schemaless APIs that change frequently without versioned contracts
Teams using programming languages not in Quicktype's supported list (e.g., niche or proprietary languages)
Environments where minimizing build-time dependencies and avoiding Node.js tooling is critical
Applications requiring extensive custom validation logic or business rules embedded directly in model serialization

Pros & Cons

Pros

Versatile Input Formats

Accepts JSON samples, JSON Schema, TypeScript, and GraphQL queries, even fetching from live API URLs, making it adaptable to various data sources without manual conversion.

Broad Language Support

Generates code for over 20 languages like Swift, Kotlin, and Python, enabling consistent type-safe models across multi-platform projects from a single schema.

Type Safety by Default

Produces strongly-typed classes or interfaces with serializers/deserializers, reducing runtime JSON parsing errors and eliminating boilerplate code for data interchange.

Build Process Integration

Offers CLI, JavaScript API, and web app, allowing easy integration into CI/CD pipelines to regenerate models from committed schemas, as shown in the README examples.

Cons

Experimental TypeScript Support

The README marks TypeScript input as experimental, which may lead to instability, limited features, or breaking changes when generating from TypeScript definitions.

Customization Complexity

Adding custom languages or renderers requires extending internal classes, as per the guide, which has a steep learning curve and is not trivial for average users.

Node.js Dependency Overhead

The CLI and JavaScript API rely on Node.js, adding tooling complexity and potential versioning issues for teams in non-JavaScript ecosystems like pure mobile or embedded development.

Frequently Asked Questions

Related Projects

Official GitHub repository

TypeScript is a superset of JavaScript that compiles to clean JavaScript output.

Stars109,158

Forks13,438

Last commit23 hours ago

DefinitelyTyped GitHub repository

The repository for high quality TypeScript type definitions.

Stars51,257

Forks30,468