diff --git a/jest.config.js b/jest.config.js
index 622dd1c9..c88638cb 100644
--- a/jest.config.js
+++ b/jest.config.js
@@ -5,7 +5,6 @@ module.exports = {
     __TEST__: true,
     __VERSION__: require('./package.json').version,
     __BROWSER__: false,
-    __BUNDLER__: true,
     __RUNTIME_COMPILE__: true,
     __GLOBAL__: false,
     __NODE_JS__: true,
diff --git a/packages/global.d.ts b/packages/global.d.ts
index 3f644c9f..11d15fea 100644
--- a/packages/global.d.ts
+++ b/packages/global.d.ts
@@ -2,7 +2,6 @@
 declare var __DEV__: boolean
 declare var __TEST__: boolean
 declare var __BROWSER__: boolean
-declare var __BUNDLER__: boolean
 declare var __RUNTIME_COMPILE__: boolean
 declare var __GLOBAL__: boolean
 declare var __NODE_JS__: boolean
diff --git a/packages/runtime-core/src/apiCreateApp.ts b/packages/runtime-core/src/apiCreateApp.ts
index 63d38616..c1e0538c 100644
--- a/packages/runtime-core/src/apiCreateApp.ts
+++ b/packages/runtime-core/src/apiCreateApp.ts
@@ -209,7 +209,7 @@ export function createAppAPI<HostElement>(
           vnode.appContext = context
 
           // HMR root reload
-          if (__BUNDLER__ && __DEV__) {
+          if (__DEV__) {
             context.reload = () => {
               render(cloneVNode(vnode), rootContainer)
             }
diff --git a/packages/runtime-core/src/componentRenderUtils.ts b/packages/runtime-core/src/componentRenderUtils.ts
index c4b04ae7..1074edf9 100644
--- a/packages/runtime-core/src/componentRenderUtils.ts
+++ b/packages/runtime-core/src/componentRenderUtils.ts
@@ -213,7 +213,6 @@ export function shouldUpdateComponent(
   // caused the child component's slots content to have changed, we need to
   // force the child to update as well.
   if (
-    __BUNDLER__ &&
     __DEV__ &&
     (prevChildren || nextChildren) &&
     parentComponent &&
diff --git a/packages/runtime-core/src/hmr.ts b/packages/runtime-core/src/hmr.ts
index cdbf91be..86115133 100644
--- a/packages/runtime-core/src/hmr.ts
+++ b/packages/runtime-core/src/hmr.ts
@@ -16,7 +16,7 @@ export interface HMRRuntime {
 // it easier to be used in toolings like vue-loader
 // Note: for a component to be eligible for HMR it also needs the __hmrId option
 // to be set so that its instances can be registered / removed.
-if (__BUNDLER__ && __DEV__) {
+if (__DEV__) {
   const globalObject: any =
     typeof global !== 'undefined'
       ? global
diff --git a/packages/runtime-core/src/renderer.ts b/packages/runtime-core/src/renderer.ts
index d143ab88..0df8576e 100644
--- a/packages/runtime-core/src/renderer.ts
+++ b/packages/runtime-core/src/renderer.ts
@@ -64,8 +64,6 @@ import { createHydrationFunctions, RootHydrateFunction } from './hydration'
 import { invokeDirectiveHook } from './directives'
 import { startMeasure, endMeasure } from './profiling'
 
-const __HMR__ = __BUNDLER__ && __DEV__
-
 export interface Renderer<HostElement = any> {
   render: RootRenderFunction<HostElement>
   createApp: CreateAppFunction<HostElement>
@@ -660,7 +658,7 @@ function baseCreateRenderer(
       invokeDirectiveHook(n2, n1, parentComponent, 'beforeUpdate')
     }
 
-    if (__HMR__ && parentComponent && parentComponent.renderUpdated) {
+    if (__DEV__ && parentComponent && parentComponent.renderUpdated) {
       // HMR updated, force full diff
       patchFlag = 0
       optimized = false
@@ -884,7 +882,7 @@ function baseCreateRenderer(
       optimized = true
     }
 
-    if (__HMR__ && parentComponent && parentComponent.renderUpdated) {
+    if (__DEV__ && parentComponent && parentComponent.renderUpdated) {
       // HMR updated, force full diff
       patchFlag = 0
       optimized = false
@@ -987,7 +985,7 @@ function baseCreateRenderer(
       parentSuspense
     ))
 
-    if (__HMR__ && instance.type.__hmrId) {
+    if (__DEV__ && instance.type.__hmrId) {
       registerHMR(instance)
     }
 
@@ -1807,7 +1805,7 @@ function baseCreateRenderer(
     parentSuspense: SuspenseBoundary | null,
     doRemove?: boolean
   ) => {
-    if (__HMR__ && instance.type.__hmrId) {
+    if (__DEV__ && instance.type.__hmrId) {
       unregisterHMR(instance)
     }
 
diff --git a/packages/runtime-core/src/vnode.ts b/packages/runtime-core/src/vnode.ts
index 2277d9fd..8f494472 100644
--- a/packages/runtime-core/src/vnode.ts
+++ b/packages/runtime-core/src/vnode.ts
@@ -200,7 +200,6 @@ export function isVNode(value: any): value is VNode {
 
 export function isSameVNodeType(n1: VNode, n2: VNode): boolean {
   if (
-    __BUNDLER__ &&
     __DEV__ &&
     n2.shapeFlag & ShapeFlags.COMPONENT &&
     (n2.type as Component).__hmrUpdated
diff --git a/rollup.config.js b/rollup.config.js
index cfa8b1ce..c48021c5 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -178,8 +178,6 @@ function createReplacePlugin(
     __TEST__: false,
     // If the build is expected to run directly in the browser (global / esm builds)
     __BROWSER__: isBrowserBuild,
-    // is targeting bundlers?
-    __BUNDLER__: isBundlerESMBuild,
     __GLOBAL__: isGlobalBuild,
     // is targeting Node (SSR)?
     __NODE_JS__: isNodeBuild,