How to configure Flow

Every Flow project contains a .flowconfig file. You can configure Flow by modifying .flowconfig. New projects or projects that are starting to use Flow can generate a default .flowconfig by running flow init.

.flowconfig format

The .flowconfig uses a custom format that vaguely resembles INI files. We are not proud of our custom format and plan to support a better format in the future. GitHub issue #153 tracks this.

The .flowconfig consists of 5 sections:


Comment support was added in v0.23.0. Lines beginning with zero or more spaces followed by an # or ; or 💩 are ignored. For example:

# This is a comment
  # This is a comment
; This is a comment
  ; This is a comment
💩 This is a comment
  💩 This is a comment

Where to put the .flowconfig

The location of the .flowconfig is significant. Flow treats the directory that contains the .flowconfig as the project root. By default Flow includes all the source code under the project root. The paths in the [include] section are relative to the project root. Some other configuration also lets you reference the project root via the macro <PROJECT_ROOT>.

Most people put the .flowconfig in the root of their project (i.e. next to the package.json). Some people put all their code in a src/ directory and therefore put the .flowconfig at src/.flowconfig.


Say you have the following directory structure, with your .flowconfig in mydir:

└── src
    ├── othercode.js
├── .flowconfig
├── build
│   ├── first.js
│   └── shim.js
├── lib
│   └── flow
├── node_modules
│   └── es6-shim
└── src
    ├── first.js
    └── shim.js

Here is an example of how you could use the .flowconfig directives.




Now flow will include a directory outside the .flowconfig path in its check, ignore the build directory and use the declarations in lib.