Kotlin JS React accessing/configuring environment variables

I’m curious how I would use .env, .env.local, etc. in my Kotlin React application. I am using gradle, and essentially I want to be able to use different values depending upon my environment. Typically I would just create my .env and access process.env.VAR_NAME and I’m good. So, I thought I would try using something like “external val process: dynamic” and then accessing my variables like so. However, it doesn’t seem to work, possibly because the .env doesn’t get picked up? Anyone solve this?

Thanks for any feedback advice. Also, on a curious note, how would one suggest using ‘create-react-kotlin-app’ in an automated build process? That’s the main reason I choose gradle. I am open to ideas and suggestions.

Thank you!

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I am using following code for my env values:

external val process: Process

external interface Process {
val env: dynamic

And then execute


I’ve tried to use your approach, but cannot access the values in .env. Do I need to setup anything else? Could you give some more background, please?


@chrisbln Could you please give some infos how to read the variables from .env. I’ve tried to follow your steps, but cannot access the configuration.


How would you expect this to work? When the JavaScript is being executed in a browser there are no environment variables like there would be in a NodeJS or JVM process. You’d need to find a way to make the values accessible in variables in the browser.

I’m doing this using Webpack’s DefinePlugin and different configuration files which are loaded in the Webpack configuration depending on whether the build is in development or production mode. Not exactly elegant but does the job.

@simonjacobs could you provide an example of your setup? much appreciated!

You can execute extra code on your webpack configuration by placing JS files in a webpack.config.d directory (docs). You can put, for example:

const webpack = require("webpack")

var one, two

if (config.mode === "production") { // the build process makes the config object available
   one = "production_one"
   two = "production_two"
else {
   one = "development_one"
   two = "development_two"
const definePlugin = new webpack.DefinePlugin(
      ENV_VAR_ONE: one,
      ENV_VAR_TWO: two


Then back in Kotlin, if you put something like:

// inside Kotlin class
val environmentVariableOne = js("ENV_VAR_ONE")
val environmentVariableTwo = js("ENV_VAR_TWO")

then you should magically find that the variables are set to the values from the config file depending on the mode. The mode can be set in Gradle:

// build.gradle.kts
kotlin { // This is the JS plugin setup. There's an extra js closure for Multiplatform
   target {
      browser {
         webpackTask {
            mode = if (condition) Mode.DEVELOPMENT else Mode.PRODUCTION 

So then you have a way to transport variables defined during the build to the code depending on environment type.