Gatsby Config API

The file gatsby-config.js defines your site’s metadata, plugins, and other general configuration. This file should be in the root of your Gatsby site.

If you created a Gatsby site with the gatsby new command, there should already be a sample configuration file in your site’s directory. Note: There are many sample configs which may be helpful to reference in the different Gatsby Example Websites.

Set up the configuration file

The configuration file should export a JavaScript object. Within this object, you can define several different configuration options.

An example gatsby-config.js file could look like this:

Configuration options

Options available to set within gatsby-config.js include:

1. siteMetadata (object)
2. plugins (array)
3. flags (object)
4. pathPrefix (string)
5. polyfill (boolean)
6. mapping (object)
7. proxy (object)
8. developMiddleware (function)

siteMetadata

When you want to reuse common pieces of data across the site (for example, your site title), you can store that data in siteMetadata:

This way you can store it in one place, and pull it whenever you need it. If you ever need to update the info, you only have to change it here.

See a full description and sample usage in Gatsby.js Tutorial Part Four.

Plugins

Plugins are Node.js packages that implement Gatsby APIs. The config file accepts an array of plugins. Some plugins may need only to be listed by name, while others may take options (see the docs for individual plugins).

Installing a plugin using a package manager like npm does not enable it in your Gatsby site. To finish adding a plugin, make sure your gatsby-config.js file has a plugins array so you can include a space for the plugins needed to build your site:

When adding multiple plugins, they should be separated by commas in the plugins array to support valid JavaScript syntax.

Plugins without options

If a plugin does not require any options, you can add its name as a string to the plugins array:

Plugins with options

Many plugins have optional or required options to configure them. Instead of adding a name string to the plugins array, add an object with its name and options. Most plugins show examples in their README file or page in the Gatsby plugin library.

Here’s an example showing how to write an object with keys to resolve the plugin name and an options object with any applicable settings:

Mixed plugins

You can add plugins with and without options in the same array. Your site’s config file could look like this:

See more about Plugins for more on utilizing plugins, and to see available official and community plugins.

Flags

Flags let sites enable experimental or upcoming changes that are still in testing or waiting for the next major release.

Go here to see a list of the current flags.

pathPrefix

It’s common for sites to be hosted somewhere other than the root of their domain. Say you have a Gatsby site at example.com/blog/. In this case, you would need a prefix (/blog) added to all paths on the site.

See more about Adding a Path Prefix.

Polyfill

Gatsby uses the ES6 Promise API. Because some browsers don’t support this, Gatsby includes a Promise polyfill by default.

If you’d like to provide your own Promise polyfill, you can set polyfill to false.

See more about Browser Support in Gatsby.

Mapping node types

Gatsby includes an advanced feature that lets you create “mappings” between node types.

Note: Gatsby v2.2 introduced a new way to create foreign-key relations between node types with the @link GraphQL field extension.

For instance, imagine you have a multi-author markdown blog where you want to “link” from each blog post to the author information stored in a YAML file named author.yaml:

You can map between the author field in frontmatter to the id in the author.yaml objects by adding to your gatsby-config.js:

You may need to install the appropriate file transformer (in this case YAML) and set up gatsby-source-filesystem properly for Gatsby to pick up the mapping files. This applies to other file types later mentioned in this segment as well.

Gatsby then uses this mapping when creating the GraphQL schema to enable you to query data from both sources:

Mapping can also be used to map an array of ids to any other collection of data. For example, if you have two JSON files experience.json and tech.json as follows:

And then add the following rule to your gatsby-config.js:

You can query the tech object via the referred ids in experience:

Mapping also works between Markdown files. For example, instead of having all authors in a YAML file, you could have info about each author in a separate Markdown file:

And then add the following rule to your gatsby-config.js:

Similarly to YAML and JSON files, mapping between Markdown files can also be used to map an array of ids.

Proxy

Setting the proxy config option will tell the develop server to proxy any unknown requests to your specified server. For example:

See more about Proxying API Requests in Develop.

Advanced proxying with developMiddleware

See more about adding develop middleware.