React Dev Tools Thinks My Site is in Dev Mode - reactjs

Question

I want to see how much of a speed boost I get from using the non dev version of everything so I built my site using my "production" webconfig. but dev tools still is telling me it is in "development" mode
This page is using the development build of React.
const merge = require("webpack-merge");
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const OptimizeCSSAssetsPlugin = require("optimize-css-assets-webpack-plugin");
var BundleAnalyzerPlugin = require('webpack-bundle-analyzer').BundleAnalyzerPlugin;
const common = require("./webpack.common.js");
module.exports = merge(common, {
// Provides process.env.NODE_ENV with value production.
// Enables FlagDependencyUsagePlugin, FlagIncludedChunksPlugin,
// ModuleConcatenationPlugin, NoEmitOnErrorsPlugin, OccurrenceOrderPlugin,
// SideEffectsFlagPlugin and UglifyJsPlugin.
mode: "production",
// see https://webpack.js.org/configuration/optimization/
optimization: {
// minimize default is true
minimizer: [
// Optimize/minimize CSS assets.
// Solves extract-text-webpack-plugin CSS duplication problem
// By default it uses cssnano but a custom CSS processor can be specified
new OptimizeCSSAssetsPlugin({})
]
},
module: {
rules: [
{
test: /\.(sa|sc|c)ss$/,
// only use MiniCssExtractPlugin in production and without style-loader
use: [MiniCssExtractPlugin.loader, "css-loader", "sass-loader"]
}
]
},
plugins: [
// Mini CSS Extract plugin extracts CSS into separate files.
// It creates a CSS file per JS file which contains CSS.
// It supports On-Demand-Loading of CSS and SourceMaps.
// It requires webpack 4 to work.
new MiniCssExtractPlugin({
filename: "[name].css",
chunkFilename: "[id].css"
}),
new BundleAnalyzerPlugin()
]
});
in my package.json
"scripts": {
"dev": "cross-env NODE_ENV=dev webpack-serve --config webpack.dev.js --open",
"prod": "cross-env NODE_ENV=prod webpack -p --config webpack.prod.js",
"qa": "cross-env NODE_ENV=QA webpack --config webpack.prod.js"
},

Answer 1

My confidence is growing that your problem stems from setting NODE_ENV to prod in your package.json. I think you should instead set it to production, or allow webpack to set it internally with the mode option in your webpack config.
The react-scripts package explicitly sets this value to production for building and searching for NODE_ENV in the facebook/react project in github project shows tons of checks for production as the value instead of prod.
Here's the index.js file for react-is, many other projects in the react source follow the same pattern:
'use strict';
if (process.env.NODE_ENV === 'production') {
module.exports = require('./cjs/react-is.production.min.js');
} else {
module.exports = require('./cjs/react-is.development.js');
}
I would try changing your build script to:
"prod": "cross-env NODE_ENV=production webpack -p --config webpack.prod.js",
or even let webpack -p set it automatically:
"prod": "cross-env webpack -p --config webpack.prod.js",