Can't access gatsby environment variables on the client side

Question

I set up .env file and gatsby-config.js as below.

// .env.development
GATSBY_API_URL=https://example.com/api

// gatsby-config.js
console.log(process.env)
...
...

Although when to run gatsby develop, it shows all env vars including GATSBY_API_URL: 'https://example.com/api', but there is no env vars on a browser.

// client side
console.log(process.env)  // => this will return {}  empty object

I think I followed https://www.gatsbyjs.org/docs/environment-variables/ as it says, and added GATSBY_ prefix to the var.

Is there a reason why I don't see the env var on the client side?

gatsby info --clipboard

  System:
    OS: macOS Sierra 10.12.6
    CPU: (4) x64 Intel(R) Core(TM) i5-4258U CPU @ 2.40GHz
    Shell: 5.2 - /bin/zsh
  Binaries:
    Node: 11.2.0 - /usr/local/bin/node
    Yarn: 1.9.4 - /usr/local/bin/yarn
    npm: 6.4.1 - /usr/local/bin/npm
  Browsers:
    Chrome: 70.0.3538.110
    Firefox: 63.0.3
    Safari: 12.0.2
  npmPackages:
    gatsby: ^2.0.61 => 2.0.61
    gatsby-image: ^2.0.22 => 2.0.22
    gatsby-plugin-google-analytics: ^2.0.8 => 2.0.8
    gatsby-plugin-manifest: ^2.0.11 => 2.0.11
    gatsby-plugin-no-sourcemaps: ^2.0.1 => 2.0.1
    gatsby-plugin-nprogress: ^2.0.7 => 2.0.7
    gatsby-plugin-react-helmet: ^3.0.4 => 3.0.4
    gatsby-plugin-sass: ^2.0.5 => 2.0.5
    gatsby-plugin-sharp: ^2.0.14 => 2.0.14
    gatsby-plugin-styled-components: ^3.0.4 => 3.0.4
    gatsby-plugin-typescript: ^2.0.2 => 2.0.2
    gatsby-plugin-typography: ^2.2.2 => 2.2.2
    gatsby-plugin-webpack-bundle-analyzer: ^1.0.3 => 1.0.3
    gatsby-source-filesystem: ^2.0.10 => 2.0.10
    gatsby-transformer-sharp: ^2.1.9 => 2.1.9
    gatsby-transformer-yaml: ^2.1.6 => 2.1.6
  npmGlobalPackages:
    gatsby-cli: 2.4.5

Answer 1

A few steps & notes that should solve your problem:

console.log(process.env) will always print empty object

To see if it's really working, you should print the variables directly, e.g. console.log(process.env.API_URL).

Make sure .env.* is in your root folder

In other words, your folder hierarchy should look something like:

.env.development
.env.production
src/
  pages/
    index.js

You don't need to prefix with GATSBY_ if you want to access env variables server-side

From the docs:

In addition to these Project Environment Variables defined in .env.* files, you could also define OS Env Vars. OS Env Vars which are prefixed with GATSBY_ will become available in browser JavaScript.

You need the GATSBY_* prefix if you are using them browser-side

The prefixing is only if you use the OS Env Vars approach (i.e. you set them directly on your server and not in these .env files).

Kill and restart gatsby develop when you've added the .env file(s)

I ran into this when reproducing on CodeSandbox (in CodeSandbox, you do the restart by going to Server Control Panel on the left, and clicking Restart Sandbox).

Here's the working example: https://codesandbox.io/s/jj8xzn2y15