next.config.js

const withPrefresh = require("@prefresh/next")

module.exports = withPrefresh({
  webpack(config, { dev, isServer }) {
    // Move Preact into the framework chunk instead of duplicating in routes:
    const splitChunks = config.optimization && config.optimization.splitChunks
    if (splitChunks) {
      const cacheGroups = splitChunks.cacheGroups
      const test = /[\\/]node_modules[\\/](preact|preact-render-to-string|preact-context-provider)[\\/]/
      if (cacheGroups.framework) {
        cacheGroups.preact = Object.assign({}, cacheGroups.framework, { test })
        // if you want to merge the 2 small commons+framework chunks:
        // cacheGroups.commons.name = 'framework';
      }
    }

    if (isServer) {
      // mark `preact` stuffs as external for server bundle to prevent duplicate copies of preact
      config.externals.push(
        /^(preact|preact-render-to-string|preact-context-provider)([\\/]|$)/
      )
    }

    // Install webpack aliases:
    const aliases = config.resolve.alias || (config.resolve.alias = {})
    aliases.react = aliases["react-dom"] = "preact/compat"

    // Automatically inject Preact DevTools:
    if (dev && !isServer) {
      const entry = config.entry
      config.entry = () =>
        entry().then((entries) => {
          entries["main.js"] = ["preact/debug"].concat(entries["main.js"] || [])
          return entries
        })
    }

    return config
  }
})