diff --git a/packages/@vue/babel-preset-app/index.js b/packages/@vue/babel-preset-app/index.js
index f2f712cc87..51b0865f62 100644
--- a/packages/@vue/babel-preset-app/index.js
+++ b/packages/@vue/babel-preset-app/index.js
@@ -43,14 +43,14 @@ function getIntersectionTargets (targets, constraintTargets) {
   return intersection
 }
 
-function getModernTargets (targets) {
-  const allModernTargets = getTargets(
+function getModuleTargets (targets) {
+  const allModuleTargets = getTargets(
     { esmodules: true },
     { ignoreBrowserslistConfig: true }
   )
 
   // use the intersection of modern mode browsers and user defined targets config
-  return getIntersectionTargets(targets, allModernTargets)
+  return getIntersectionTargets(targets, allModuleTargets)
 }
 
 function getWCTargets (targets) {
@@ -177,7 +177,7 @@ module.exports = (context, options = {}) => {
     targets = getWCTargets(targets)
   } else if (process.env.VUE_CLI_MODERN_BUILD) {
     // targeting browsers that at least support <script type="module">
-    targets = getModernTargets(targets)
+    targets = getModuleTargets(targets)
   }
 
   // included-by-default polyfills. These are common polyfills that 3rd party
diff --git a/packages/@vue/cli-service/__tests__/modernMode.spec.js b/packages/@vue/cli-service/__tests__/modernMode.spec.js
index 1368838db9..1be69c300d 100644
--- a/packages/@vue/cli-service/__tests__/modernMode.spec.js
+++ b/packages/@vue/cli-service/__tests__/modernMode.spec.js
@@ -103,7 +103,7 @@ test('should inject nomodule-fix script when Safari 10 support is required', asy
   let { stdout } = await project.run('vue-cli-service build')
   let index = await project.read('dist/index.html')
   // should inject Safari 10 nomodule fix as an inline script
-  const { safariFix } = require('../lib/webpack/ModernModePlugin')
+  const { safariFix } = require('../lib/webpack/SafariNomoduleFixPlugin')
   expect(index).toMatch(`<script>${safariFix}</script>`)
 
   // `--no-unsafe-inline` option
@@ -130,6 +130,36 @@ test('--no-module', async () => {
   expect(files.some(f => /-legacy.js/.test(f))).toBe(false)
 })
 
+test('should use correct hash for fallback bundles', async () => {
+  const project = await create('legacy-hash', defaultPreset)
+
+  const { stdout } = await project.run('vue-cli-service build')
+  expect(stdout).toMatch('Build complete.')
+
+  const index = await project.read('dist/index.html')
+  const jsFiles = (await fs.readdir(path.join(project.dir, 'dist/js'))).filter(f => f.endsWith('.js'))
+  for (const f of jsFiles) {
+    expect(index).toMatch(`<script defer="defer" src="/js/${f}"`)
+  }
+})
+
+test('should only build one bundle if all targets support ES module', async () => {
+  const project = await create('no-differential-loading', defaultPreset)
+
+  const pkg = JSON.parse(await project.read('package.json'))
+  pkg.browserslist.push('not ie <= 11')
+  await project.write('package.json', JSON.stringify(pkg, null, 2))
+
+  const { stdout } = await project.run('vue-cli-service build')
+  expect(stdout).toMatch('Build complete.')
+
+  const index = await project.read('dist/index.html')
+  expect(index).not.toMatch('type="module"')
+
+  const files = await fs.readdir(path.join(project.dir, 'dist/js'))
+  expect(files.some(f => /-legacy.js/.test(f))).toBe(false)
+})
+
 afterAll(async () => {
   if (browser) {
     await browser.close()
diff --git a/packages/@vue/cli-service/bin/vue-cli-service.js b/packages/@vue/cli-service/bin/vue-cli-service.js
index adfe811c3c..126acecab9 100755
--- a/packages/@vue/cli-service/bin/vue-cli-service.js
+++ b/packages/@vue/cli-service/bin/vue-cli-service.js
@@ -18,6 +18,7 @@ const rawArgv = process.argv.slice(2)
 const args = require('minimist')(rawArgv, {
   boolean: [
     // build
+    // FIXME: --no-module, --no-unsafe-inline, no-clean, etc.
     'modern',
     'report',
     'report-json',
diff --git a/packages/@vue/cli-service/lib/commands/build/index.js b/packages/@vue/cli-service/lib/commands/build/index.js
index fcad4278d8..0b5ff894cd 100644
--- a/packages/@vue/cli-service/lib/commands/build/index.js
+++ b/packages/@vue/cli-service/lib/commands/build/index.js
@@ -53,35 +53,43 @@ module.exports = (api, options) => {
     }
 
     process.env.VUE_CLI_BUILD_TARGET = args.target
-    if (args.module && args.target === 'app') {
-      process.env.VUE_CLI_MODERN_MODE = true
-      if (!process.env.VUE_CLI_MODERN_BUILD) {
-        // main-process for legacy build
-        await build(Object.assign({}, args, {
-          modernBuild: false,
-          keepAlive: true
-        }), api, options)
-        // spawn sub-process of self for modern build
-        const { execa } = require('@vue/cli-shared-utils')
-        const cliBin = require('path').resolve(__dirname, '../../../bin/vue-cli-service.js')
-        await execa('node', [cliBin, 'build', ...rawArgs], {
-          stdio: 'inherit',
-          env: {
-            VUE_CLI_MODERN_BUILD: true
-          }
-        })
-      } else {
-        // sub-process for modern build
-        await build(Object.assign({}, args, {
-          modernBuild: true,
-          clean: false
-        }), api, options)
-      }
-      delete process.env.VUE_CLI_MODERN_MODE
-    } else {
+
+    const { log, execa } = require('@vue/cli-shared-utils')
+    const { allProjectTargetsSupportModule } = require('../../util/targets')
+
+    let needsDifferentialLoading = args.target === 'app' && args.module
+    if (allProjectTargetsSupportModule) {
+      log(
+        `All browser targets in the browserslist configuration have supported ES module.\n` +
+        `Therefore we don't build two separate bundles for differential loading.\n`
+      )
+      needsDifferentialLoading = false
+    }
+
+    if (!needsDifferentialLoading) {
       await build(args, api, options)
+      return
+    }
+
+    process.env.VUE_CLI_MODERN_MODE = true
+    if (!process.env.VUE_CLI_MODERN_BUILD) {
+      // main-process for legacy build
+      const legacyBuildArgs = { ...args, moduleBuild: false, keepAlive: true }
+      await build(legacyBuildArgs, api, options)
+
+      // spawn sub-process of self for modern build
+      const cliBin = require('path').resolve(__dirname, '../../../bin/vue-cli-service.js')
+      await execa('node', [cliBin, 'build', ...rawArgs], {
+        stdio: 'inherit',
+        env: {
+          VUE_CLI_MODERN_BUILD: true
+        }
+      })
+    } else {
+      // sub-process for modern build
+      const moduleBuildArgs = { ...args, moduleBuild: true, clean: false }
+      await build(moduleBuildArgs, api, options)
     }
-    delete process.env.VUE_CLI_BUILD_TARGET
   })
 }
 
@@ -104,8 +112,8 @@ async function build (args, api, options) {
   const mode = api.service.mode
   if (args.target === 'app') {
     const bundleTag = args.module
-      ? args.modernBuild
-        ? `modern bundle `
+      ? args.moduleBuild
+        ? `module bundle `
         : `legacy bundle `
       : ``
     logWithSpinner(`Building ${bundleTag}for ${mode}...`)
@@ -125,7 +133,7 @@ async function build (args, api, options) {
   }
 
   const targetDir = api.resolve(options.outputDir)
-  const isLegacyBuild = args.target === 'app' && args.module && !args.modernBuild
+  const isLegacyBuild = args.target === 'app' && args.module && !args.moduleBuild
 
   // resolve raw webpack config
   let webpackConfig
@@ -162,7 +170,7 @@ async function build (args, api, options) {
     modifyConfig(webpackConfig, config => {
       config.plugins.push(new DashboardPlugin({
         type: 'build',
-        modernBuild: args.modernBuild,
+        moduleBuild: args.moduleBuild,
         keepAlive: args.keepAlive
       }))
     })
diff --git a/packages/@vue/cli-service/lib/commands/build/resolveAppConfig.js b/packages/@vue/cli-service/lib/commands/build/resolveAppConfig.js
index b8f518af4c..3ab09b3000 100644
--- a/packages/@vue/cli-service/lib/commands/build/resolveAppConfig.js
+++ b/packages/@vue/cli-service/lib/commands/build/resolveAppConfig.js
@@ -17,29 +17,35 @@ module.exports = (api, args, options) => {
     })
   }
 
-  if (args.module) {
+  if (process.env.VUE_CLI_MODERN_MODE) {
     const ModernModePlugin = require('../../webpack/ModernModePlugin')
-    if (!args.modernBuild) {
+    const SafariNomoduleFixPlugin = require('../../webpack/SafariNomoduleFixPlugin')
+
+    if (!args.moduleBuild) {
       // Inject plugin to extract build stats and write to disk
       config
-        .plugin('modern-mode-legacy')
-        .use(ModernModePlugin, [{
-          targetDir,
-          isModernBuild: false,
-          unsafeInline: args['unsafe-inline']
-        }])
+      .plugin('modern-mode-legacy')
+      .use(ModernModePlugin, [{
+        targetDir,
+        isModuleBuild: false
+      }])
     } else {
-      // Inject plugin to read non-modern build stats and inject HTML
       config
-        .plugin('modern-mode-modern')
-        .use(ModernModePlugin, [{
-          targetDir,
-          isModernBuild: true,
+        .plugin('safari-nomodule-fix')
+        .use(SafariNomoduleFixPlugin, [{
           unsafeInline: args['unsafe-inline'],
           // as we may generate an addition file asset (if `no-unsafe-inline` specified)
           // we need to provide the correct directory for that file to place in
           jsDirectory: require('../../util/getAssetPath')(options, 'js')
         }])
+
+      // Inject plugin to read non-modern build stats and inject HTML
+      config
+        .plugin('modern-mode-modern')
+        .use(ModernModePlugin, [{
+          targetDir,
+          isModuleBuild: true
+        }])
     }
   }
 
diff --git a/packages/@vue/cli-service/lib/util/targets.js b/packages/@vue/cli-service/lib/util/targets.js
index bd2ce6b20c..862aa91109 100644
--- a/packages/@vue/cli-service/lib/util/targets.js
+++ b/packages/@vue/cli-service/lib/util/targets.js
@@ -3,7 +3,8 @@
 const { semver } = require('@vue/cli-shared-utils')
 const { default: getTargets } = require('@babel/helper-compilation-targets')
 
-const allModernTargets = getTargets(
+// See the result at <https://github.com/babel/babel/blob/v7.13.15/packages/babel-compat-data/data/native-modules.json>
+const allModuleTargets = getTargets(
   { esmodules: true },
   { ignoreBrowserslistConfig: true }
 )
@@ -32,19 +33,38 @@ function getIntersectionTargets (targets, constraintTargets) {
   return intersection
 }
 
-function getModernTargets (targets) {
+function getModuleTargets (targets) {
   // use the intersection of modern mode browsers and user defined targets config
-  return getIntersectionTargets(targets, allModernTargets)
+  return getIntersectionTargets(targets, allModuleTargets)
 }
 
+function doAllTargetsSupportModule (targets) {
+  const browserList = Object.keys(targets)
+
+  return browserList.every(browserName => {
+    if (!allModuleTargets[browserName]) {
+      return false
+    }
+
+    return semver.gte(
+      semver.coerce(targets[browserName]),
+      semver.coerce(allModuleTargets[browserName])
+    )
+  })
+}
+
+// get browserslist targets in current working directory
 const projectTargets = getTargets()
-const projectModernTargets = getModernTargets(projectTargets)
+const projectModuleTargets = getModuleTargets(projectTargets)
+const allProjectTargetsSupportModule = doAllTargetsSupportModule(projectTargets)
 
 module.exports = {
   getTargets,
-  getModernTargets,
+  getModuleTargets,
   getIntersectionTargets,
+  doAllTargetsSupportModule,
 
   projectTargets,
-  projectModernTargets
+  projectModuleTargets,
+  allProjectTargetsSupportModule
 }
diff --git a/packages/@vue/cli-service/lib/webpack/DashboardPlugin.js b/packages/@vue/cli-service/lib/webpack/DashboardPlugin.js
index 3364e1ffab..439e0be353 100644
--- a/packages/@vue/cli-service/lib/webpack/DashboardPlugin.js
+++ b/packages/@vue/cli-service/lib/webpack/DashboardPlugin.js
@@ -33,7 +33,7 @@ function getTimeMessage (timer) {
 class DashboardPlugin {
   constructor (options) {
     this.type = options.type
-    if (this.type === 'build' && options.modernBuild) {
+    if (this.type === 'build' && options.moduleBuild) {
       this.type = 'build-modern'
     }
     this.watching = false
diff --git a/packages/@vue/cli-service/lib/webpack/ModernModePlugin.js b/packages/@vue/cli-service/lib/webpack/ModernModePlugin.js
index 180143465c..e6632b4417 100644
--- a/packages/@vue/cli-service/lib/webpack/ModernModePlugin.js
+++ b/packages/@vue/cli-service/lib/webpack/ModernModePlugin.js
@@ -1,33 +1,17 @@
 const fs = require('fs-extra')
 const path = require('path')
 const HtmlWebpackPlugin = require('html-webpack-plugin')
-
-const { semver } = require('@vue/cli-shared-utils')
-const { projectModernTargets } = require('../util/targets')
-
-const minSafariVersion = projectModernTargets.safari
-const minIOSVersion = projectModernTargets.ios
-const supportsSafari10 =
-  (minSafariVersion && semver.lt(semver.coerce(minSafariVersion), '11.0.0')) ||
-  (minIOSVersion && semver.lt(semver.coerce(minIOSVersion), '11.0.0'))
-const needsSafariFix = supportsSafari10
-
-// https://gist.github.com/samthor/64b114e4a4f539915a95b91ffd340acc
-const safariFix = `!function(){var e=document,t=e.createElement("script");if(!("noModule"in t)&&"onbeforeload"in t){var n=!1;e.addEventListener("beforeload",function(e){if(e.target===t)n=!0;else if(!e.target.hasAttribute("nomodule")||!n)return;e.preventDefault()},!0),t.type="module",t.src=".",e.head.appendChild(t),t.remove()}}();`
-
 class ModernModePlugin {
-  constructor ({ targetDir, isModernBuild, unsafeInline, jsDirectory }) {
+  constructor ({ targetDir, isModuleBuild }) {
     this.targetDir = targetDir
-    this.isModernBuild = isModernBuild
-    this.unsafeInline = unsafeInline
-    this.jsDirectory = jsDirectory
+    this.isModuleBuild = isModuleBuild
   }
 
   apply (compiler) {
-    if (!this.isModernBuild) {
+    if (!this.isModuleBuild) {
       this.applyLegacy(compiler)
     } else {
-      this.applyModern(compiler)
+      this.applyModule(compiler)
     }
   }
 
@@ -53,7 +37,7 @@ class ModernModePlugin {
     })
   }
 
-  applyModern (compiler) {
+  applyModule (compiler) {
     const ID = `vue-cli-modern-bundle`
     compiler.hooks.compilation.tap(ID, compilation => {
       HtmlWebpackPlugin.getHooks(compilation).alterAssetTagGroups.tapAsync(ID, async (data, cb) => {
@@ -87,36 +71,6 @@ class ModernModePlugin {
           .filter(a => a.tagName === 'script' && a.attributes)
         legacyAssets.forEach(a => { a.attributes.nomodule = '' })
 
-        if (needsSafariFix) {
-          if (this.unsafeInline) {
-            // inject inline Safari 10 nomodule fix
-            tags.push({
-              tagName: 'script',
-              closeTag: true,
-              innerHTML: safariFix
-            })
-          } else {
-            // inject the fix as an external script
-            const safariFixPath = path.join(this.jsDirectory, 'safari-nomodule-fix.js')
-            const fullSafariFixPath = path.join(compilation.options.output.publicPath, safariFixPath)
-            compilation.assets[safariFixPath] = {
-              source: function () {
-                return Buffer.from(safariFix)
-              },
-              size: function () {
-                return Buffer.byteLength(safariFix)
-              }
-            }
-            tags.push({
-              tagName: 'script',
-              closeTag: true,
-              attributes: {
-                src: fullSafariFixPath
-              }
-            })
-          }
-        }
-
         tags.push(...legacyAssets)
         await fs.remove(tempFilename)
         cb()
@@ -129,5 +83,4 @@ class ModernModePlugin {
   }
 }
 
-ModernModePlugin.safariFix = safariFix
 module.exports = ModernModePlugin
diff --git a/packages/@vue/cli-service/lib/webpack/SafariNomoduleFixPlugin.js b/packages/@vue/cli-service/lib/webpack/SafariNomoduleFixPlugin.js
new file mode 100644
index 0000000000..fef45a6416
--- /dev/null
+++ b/packages/@vue/cli-service/lib/webpack/SafariNomoduleFixPlugin.js
@@ -0,0 +1,75 @@
+// https://gist.github.com/samthor/64b114e4a4f539915a95b91ffd340acc
+const safariFix = `!function(){var e=document,t=e.createElement("script");if(!("noModule"in t)&&"onbeforeload"in t){var n=!1;e.addEventListener("beforeload",function(e){if(e.target===t)n=!0;else if(!e.target.hasAttribute("nomodule")||!n)return;e.preventDefault()},!0),t.type="module",t.src=".",e.head.appendChild(t),t.remove()}}();`
+
+const path = require('path')
+const HtmlWebpackPlugin = require('html-webpack-plugin')
+const { semver } = require('@vue/cli-shared-utils')
+const { projectModuleTargets } = require('../util/targets')
+
+const minSafariVersion = projectModuleTargets.safari
+const minIOSVersion = projectModuleTargets.ios
+const supportsSafari10 =
+  (minSafariVersion && semver.lt(semver.coerce(minSafariVersion), '11.0.0')) ||
+  (minIOSVersion && semver.lt(semver.coerce(minIOSVersion), '11.0.0'))
+const needsSafariFix = supportsSafari10
+
+class SafariNomoduleFixPlugin {
+  constructor ({ unsafeInline, jsDirectory }) {
+    this.unsafeInline = unsafeInline
+    this.jsDirectory = jsDirectory
+  }
+
+  apply (compiler) {
+    if (!needsSafariFix) {
+      return
+    }
+
+    const ID = 'SafariNomoduleFixPlugin'
+    compiler.hooks.compilation.tap(ID, compilation => {
+      HtmlWebpackPlugin.getHooks(compilation).alterAssetTagGroups.tap(ID, data => {
+        let scriptTag
+
+        if (this.unsafeInline) {
+          // inject inline Safari 10 nomodule fix
+          scriptTag = {
+            tagName: 'script',
+            closeTag: true,
+            innerHTML: safariFix
+          }
+        } else {
+          // inject the fix as an external script
+          const safariFixPath = path.join(this.jsDirectory, 'safari-nomodule-fix.js')
+          const fullSafariFixPath = path.join(compilation.options.output.publicPath, safariFixPath)
+          compilation.assets[safariFixPath] = {
+            source: function () {
+              return Buffer.from(safariFix)
+            },
+            size: function () {
+              return Buffer.byteLength(safariFix)
+            }
+          }
+          scriptTag = {
+            tagName: 'script',
+            closeTag: true,
+            attributes: {
+              src: fullSafariFixPath
+            }
+          }
+        }
+
+        let tags = data.bodyTags
+        if (data.plugin.options.scriptLoading === 'defer') {
+          tags = data.headTags
+        }
+
+        // insert just before the first actual script tag,
+        // and after all other tags such as `meta`
+        const firstScriptIndex = tags.findIndex(tag => tag.tagName === 'script')
+        tags.splice(firstScriptIndex, 0, scriptTag)
+      })
+    })
+  }
+}
+
+SafariNomoduleFixPlugin.safariFix = safariFix
+module.exports = SafariNomoduleFixPlugin