Documentation

Guides and references for all you need to know about Flow.

📄️ Introduction

Never used a type system before or just new to Flow? Let's get you up and running in a few minutes.

Have a question about using Flow? Check here first!

Learn how to add Flow type annotations to your code: Primitives, Objects, Functions, Classes, and more.

In JavaScript there are many types of values: numbers, strings, booleans,

Learn how to use Flow to effectively type common and advanced React patterns.

Define a fixed set of constants which create their own type. Exhaustively checked in switch statements.

Learn how to write types in .flow files.

Learn how to create and use library definitions for the third-party code your code depends on.

Learn how to suppress Flow's type errors.

Learn how to configure Flow's linter to find potentially harmful code.

Learn how to enable stricter type checking on a file-by-file basis.

How to use Flow from the command line. Including how to manage the Flow background process.

Flow tries to work out of the box as much as possible, but can be configured to work with any codebase.

Flow and Babel are designed to work great together. It

Detailed guides, tips, and resources on how to integrate Flow with different code editors.