diff --git a/packages/angular_devkit/build_angular/src/differential-loading/create-webpack-multi-config.ts b/packages/angular_devkit/build_angular/src/differential-loading/create-webpack-multi-config.ts
new file mode 100644
index 000000000000..2d7c424c2788
--- /dev/null
+++ b/packages/angular_devkit/build_angular/src/differential-loading/create-webpack-multi-config.ts
@@ -0,0 +1,185 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+
+//  This updates a webpack configuration which has been created by a
+//  webpack-based builder for differential loading. It duplicates an
+//  existing one and modifies e. g. the name of the bundles to generate
+//  ([name].modern.js instead of [name].js), the resolve array, and
+//  the Angular Compiler Plugin’s reference to the tsconfig.json to use.
+//
+//  see: https://docs.google.com/document/d/13k84oGwrEjwPyAiAjUgaaM7YHJrzYXz7Cbt6CwRp9N4/
+
+
+import { AngularCompilerPlugin } from '@ngtools/webpack';
+import * as webpack from 'webpack';
+
+const StatsPlugin = require('stats-webpack-plugin');
+
+
+export function createWebpackMultiConfig(config: webpack.Configuration): webpack.Configuration[] {
+
+  const legacyConfig: webpack.Configuration = {
+    ...config,
+    output: buildLegacyOutput(config),
+    plugins: buildLegacyPlugins(config),
+    resolve: buildLegacyResolve(config),
+  };
+
+  const modernConfig: webpack.Configuration = {
+    ...config,
+    output: buildModernOutput(config),
+    plugins: buildModernPlugins(config),
+    entry: buildModernEntry(config),
+    resolve: buildModernResolve(config),
+  };
+
+  const newConfig = [legacyConfig, modernConfig];
+
+  return newConfig;
+}
+
+function buildLegacyOutput(config: webpack.Configuration): webpack.Output | undefined {
+
+  if (!config.output || !config.output.filename) {
+    return config.output;
+  }
+
+  const filename = config.output.filename.replace('[name]', '[name].legacy');
+
+  return { ...config.output, filename };
+}
+
+function buildModernOutput(config: webpack.Configuration): webpack.Output | undefined  {
+
+  if (!config.output || !config.output.filename) {
+    return config.output;
+  }
+
+  const filename = config.output.filename.replace('[name]', '[name].modern');
+
+  return { ...config.output, filename };
+}
+
+function buildModernResolve(config: webpack.Configuration): webpack.Resolve | undefined {
+
+  if (!config.resolve || !config.resolve.mainFields) {
+    return config.resolve;
+  }
+
+  const modernResolve = { ...config.resolve };
+  modernResolve.mainFields = ['es2015', 'module', 'browser', 'main'];
+
+  return modernResolve;
+}
+
+function buildLegacyResolve(config: webpack.Configuration): webpack.Resolve | undefined {
+
+  if (!config.resolve || !config.resolve.mainFields) {
+    return config.resolve;
+  }
+
+  const modernResolve = { ...config.resolve };
+  modernResolve.mainFields = ['module', 'browser', 'main'];
+
+  return modernResolve;
+}
+
+function buildModernEntry(config: webpack.Configuration): webpack.Entry | undefined {
+  const entry = config.entry;
+
+  if (!entry) {
+    return undefined;
+  }
+
+  const polyfillsEntry = entry as webpack.Entry;
+
+  const polyfills: string[] = polyfillsEntry['polyfills'] as string[];
+
+  if (!polyfills) {
+    return { ...polyfillsEntry };
+  }
+
+  const tweakPolyfills = (file: string) => {
+
+    // TODO: Do we need an own polyfill file for modern browsers? If yes, where is it created?
+
+    if (file.endsWith('polyfills.ts')) {
+      return file.replace('polyfills.ts', 'polyfills.modern.ts');
+    } else {
+      return file;
+    }
+  };
+
+  const modernPolyfills = polyfills.map(tweakPolyfills);
+  const modernEntry = { ...entry as webpack.Entry, polyfills: modernPolyfills };
+
+  return modernEntry;
+}
+
+function buildLegacyPlugins(config: webpack.Configuration): webpack.Plugin[] | undefined {
+  const plugins = config.plugins;
+
+  if (!plugins) {
+    return plugins;
+  }
+
+  const legacyPlugins = [...plugins];
+
+  const acpIndex = plugins.findIndex(p => p.constructor.name === 'AngularCompilerPlugin');
+  const acp = plugins[acpIndex] as AngularCompilerPlugin;
+  const legacyAcp = buildLegacyAngularCompilerPlugin(acp);
+  legacyPlugins[acpIndex] = legacyAcp;
+
+  return legacyPlugins;
+}
+
+function buildModernPlugins(config: webpack.Configuration): webpack.Plugin[] {
+  const plugins = config.plugins;
+
+  if (!plugins) {
+    return [];
+  }
+
+  const modernPlugins = [...plugins];
+
+  const statsPluginIndex = plugins.findIndex(p => p.constructor.name === 'StatsPlugin');
+  if (statsPluginIndex > -1) {
+    const modernStatsPlugin = buildModernStatsPlugin();
+    modernPlugins[statsPluginIndex] = modernStatsPlugin;
+  }
+
+  return modernPlugins;
+}
+
+function buildModernStatsPlugin(): webpack.Plugin {
+  const modernStatsPlugin = new StatsPlugin();
+  modernStatsPlugin.output = 'stats.modern.json';
+
+  return modernStatsPlugin;
+}
+
+function buildLegacyAngularCompilerPlugin(acp: AngularCompilerPlugin): AngularCompilerPlugin {
+  const options = acp.options;
+  const modernOptions = { ...options };
+
+  // TODO: Where shall we create this tsconfig with target=es5?
+  //  Schematics? On the fly if it does not exist?
+
+  let tsConfigPath = modernOptions.tsConfigPath;
+  if (tsConfigPath.endsWith('.json')) {
+    tsConfigPath = tsConfigPath.substr(0, tsConfigPath.length - 5);
+  }
+  tsConfigPath += '.legacy.json';
+
+  modernOptions.tsConfigPath = tsConfigPath;
+
+  const legacyAcp = new AngularCompilerPlugin(modernOptions);
+
+  return legacyAcp;
+}
diff --git a/packages/angular_devkit/build_angular/test/differential-loading/webpack_config_spec.ts b/packages/angular_devkit/build_angular/test/differential-loading/webpack_config_spec.ts
new file mode 100644
index 000000000000..750e47d88153
--- /dev/null
+++ b/packages/angular_devkit/build_angular/test/differential-loading/webpack_config_spec.ts
@@ -0,0 +1,46 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import { AngularCompilerPlugin } from '@ngtools/webpack';
+import * as path from 'path';
+import {
+  createWebpackMultiConfig,
+} from '../../src/differential-loading/create-webpack-multi-config';
+
+const devkitRoot = (global as any)._DevKitRoot; // tslint:disable-line:no-any
+const workspaceRoot = path.join(
+  devkitRoot,
+  'tests/angular_devkit/build_angular/test-differential-loading/');
+
+const tsConfig = path.join(workspaceRoot, 'tsconfig.test.json');
+
+describe('differential loading webpack config', () => {
+
+  it('will be updated', () => {
+
+    const config = {
+      output: {
+        filename: '[name].js',
+      },
+      resolve: {
+        mainFields: ['main'],
+      },
+      entry: {
+        'main': 'main.js',
+      },
+      plugins: [
+        new AngularCompilerPlugin({tsConfigPath: tsConfig }),
+      ],
+    };
+
+    const newConfig = createWebpackMultiConfig(config);
+
+    expect(Array.isArray(newConfig)).toBe(true);
+    expect(newConfig.length).toBe(2);
+  });
+});
diff --git a/tests/angular_devkit/build_angular/test-differential-loading/main.ts b/tests/angular_devkit/build_angular/test-differential-loading/main.ts
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/tests/angular_devkit/build_angular/test-differential-loading/tsconfig.test.json b/tests/angular_devkit/build_angular/test-differential-loading/tsconfig.test.json
new file mode 100644
index 000000000000..944d93dc8215
--- /dev/null
+++ b/tests/angular_devkit/build_angular/test-differential-loading/tsconfig.test.json
@@ -0,0 +1,21 @@
+{
+  "compileOnSave": false,
+  "compilerOptions": {
+    "baseUrl": "./",
+    "outDir": "./dist/out-tsc",
+    "sourceMap": true,
+    "declaration": false,
+    "moduleResolution": "node",
+    "emitDecoratorMetadata": true,
+    "experimentalDecorators": true,
+    "target": "es2015",
+    "module": "esnext",
+    "typeRoots": [
+      "node_modules/@types"
+    ],
+    "lib": [
+      "es2017",
+      "dom"
+    ]
+  }
+}
diff --git a/tests/angular_devkit/build_angular/test-differential-loading/tsconfig.test.legacy.json b/tests/angular_devkit/build_angular/test-differential-loading/tsconfig.test.legacy.json
new file mode 100644
index 000000000000..cabc4606d16f
--- /dev/null
+++ b/tests/angular_devkit/build_angular/test-differential-loading/tsconfig.test.legacy.json
@@ -0,0 +1,21 @@
+{
+  "compileOnSave": false,
+  "compilerOptions": {
+    "baseUrl": "./",
+    "outDir": "./dist/out-tsc",
+    "sourceMap": true,
+    "declaration": false,
+    "moduleResolution": "node",
+    "emitDecoratorMetadata": true,
+    "experimentalDecorators": true,
+    "target": "es5",
+    "module": "esnext",
+    "typeRoots": [
+      "node_modules/@types"
+    ],
+    "lib": [
+      "es2017",
+      "dom"
+    ]
+  }
+}