diff --git a/packages/react-dom/src/__tests__/ReactDOMServerIntegrationHooks-test.js b/packages/react-dom/src/__tests__/ReactDOMServerIntegrationHooks-test.js
index 397b739546dcc..3242fdd3e81f4 100644
--- a/packages/react-dom/src/__tests__/ReactDOMServerIntegrationHooks-test.js
+++ b/packages/react-dom/src/__tests__/ReactDOMServerIntegrationHooks-test.js
@@ -736,17 +736,6 @@ describe('ReactDOMServerHooks', () => {
     },
   );
 
-  itRenders('warns when bitmask is passed to useContext', async render => {
-    const Context = React.createContext('Hi');
-
-    function Foo() {
-      return <span>{useContext(Context, 1)}</span>;
-    }
-
-    const domNode = await render(<Foo />, 1);
-    expect(domNode.textContent).toBe('Hi');
-  });
-
   describe('useDebugValue', () => {
     itRenders('is a noop', async render => {
       function Counter(props) {
@@ -760,11 +749,11 @@ describe('ReactDOMServerHooks', () => {
   });
 
   describe('readContext', () => {
-    function readContext(Context, observedBits) {
+    function readContext(Context) {
       const dispatcher =
         React.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED
           .ReactCurrentDispatcher.current;
-      return dispatcher.readContext(Context, observedBits);
+      return dispatcher.readContext(Context);
     }
 
     itRenders(
diff --git a/packages/react-reconciler/src/ReactFiberBeginWork.new.js b/packages/react-reconciler/src/ReactFiberBeginWork.new.js
index 345f668fc62e8..dd88f1beb8fd1 100644
--- a/packages/react-reconciler/src/ReactFiberBeginWork.new.js
+++ b/packages/react-reconciler/src/ReactFiberBeginWork.new.js
@@ -160,7 +160,6 @@ import {
   checkIfContextChanged,
   readContext,
   prepareToReadContext,
-  calculateChangedBits,
   scheduleWorkOnParentPath,
 } from './ReactFiberNewContext.new';
 import {renderWithHooks, bailoutHooks} from './ReactFiberHooks.new';
@@ -221,7 +220,7 @@ import {
   restoreSpawnedCachePool,
   getOffscreenDeferredCachePool,
 } from './ReactFiberCacheComponent.new';
-import {MAX_SIGNED_31_BIT_INT} from './MaxInts';
+import is from 'shared/objectIs';
 
 import {disableLogs, reenableLogs} from 'shared/ConsolePatchingDev';
 
@@ -796,12 +795,7 @@ function updateCacheComponent(
       pushCacheProvider(workInProgress, nextCache);
       if (nextCache !== prevState.cache) {
         // This cache refreshed. Propagate a context change.
-        propagateContextChange(
-          workInProgress,
-          CacheContext,
-          MAX_SIGNED_31_BIT_INT,
-          renderLanes,
-        );
+        propagateContextChange(workInProgress, CacheContext, renderLanes);
       }
     }
   }
@@ -1168,12 +1162,7 @@ function updateHostRoot(current, workInProgress, renderLanes) {
     pushCacheProvider(workInProgress, nextCache);
     if (nextCache !== prevState.cache) {
       // The root cache refreshed.
-      propagateContextChange(
-        workInProgress,
-        CacheContext,
-        MAX_SIGNED_31_BIT_INT,
-        renderLanes,
-      );
+      propagateContextChange(workInProgress, CacheContext, renderLanes);
     }
   }
 
@@ -3007,8 +2996,7 @@ function updateContextProvider(
   } else {
     if (oldProps !== null) {
       const oldValue = oldProps.value;
-      const changedBits = calculateChangedBits(context, newValue, oldValue);
-      if (changedBits === 0) {
+      if (is(oldValue, newValue)) {
         // No change. Bailout early if children are the same.
         if (
           oldProps.children === newProps.children &&
@@ -3023,12 +3011,7 @@ function updateContextProvider(
       } else {
         // The context value changed. Search for matching consumers and schedule
         // them to update.
-        propagateContextChange(
-          workInProgress,
-          context,
-          changedBits,
-          renderLanes,
-        );
+        propagateContextChange(workInProgress, context, renderLanes);
       }
     }
   }
@@ -3086,7 +3069,7 @@ function updateContextConsumer(
   }
 
   prepareToReadContext(workInProgress, renderLanes);
-  const newValue = readContext(context, newProps.unstable_observedBits);
+  const newValue = readContext(context);
   let newChildren;
   if (__DEV__) {
     ReactCurrentOwner.current = workInProgress;
diff --git a/packages/react-reconciler/src/ReactFiberBeginWork.old.js b/packages/react-reconciler/src/ReactFiberBeginWork.old.js
index 72b4e33431b00..1dd3ff43ffac1 100644
--- a/packages/react-reconciler/src/ReactFiberBeginWork.old.js
+++ b/packages/react-reconciler/src/ReactFiberBeginWork.old.js
@@ -160,7 +160,6 @@ import {
   checkIfContextChanged,
   readContext,
   prepareToReadContext,
-  calculateChangedBits,
   scheduleWorkOnParentPath,
 } from './ReactFiberNewContext.old';
 import {renderWithHooks, bailoutHooks} from './ReactFiberHooks.old';
@@ -221,7 +220,7 @@ import {
   restoreSpawnedCachePool,
   getOffscreenDeferredCachePool,
 } from './ReactFiberCacheComponent.old';
-import {MAX_SIGNED_31_BIT_INT} from './MaxInts';
+import is from 'shared/objectIs';
 
 import {disableLogs, reenableLogs} from 'shared/ConsolePatchingDev';
 
@@ -796,12 +795,7 @@ function updateCacheComponent(
       pushCacheProvider(workInProgress, nextCache);
       if (nextCache !== prevState.cache) {
         // This cache refreshed. Propagate a context change.
-        propagateContextChange(
-          workInProgress,
-          CacheContext,
-          MAX_SIGNED_31_BIT_INT,
-          renderLanes,
-        );
+        propagateContextChange(workInProgress, CacheContext, renderLanes);
       }
     }
   }
@@ -1168,12 +1162,7 @@ function updateHostRoot(current, workInProgress, renderLanes) {
     pushCacheProvider(workInProgress, nextCache);
     if (nextCache !== prevState.cache) {
       // The root cache refreshed.
-      propagateContextChange(
-        workInProgress,
-        CacheContext,
-        MAX_SIGNED_31_BIT_INT,
-        renderLanes,
-      );
+      propagateContextChange(workInProgress, CacheContext, renderLanes);
     }
   }
 
@@ -3007,8 +2996,7 @@ function updateContextProvider(
   } else {
     if (oldProps !== null) {
       const oldValue = oldProps.value;
-      const changedBits = calculateChangedBits(context, newValue, oldValue);
-      if (changedBits === 0) {
+      if (is(oldValue, newValue)) {
         // No change. Bailout early if children are the same.
         if (
           oldProps.children === newProps.children &&
@@ -3023,12 +3011,7 @@ function updateContextProvider(
       } else {
         // The context value changed. Search for matching consumers and schedule
         // them to update.
-        propagateContextChange(
-          workInProgress,
-          context,
-          changedBits,
-          renderLanes,
-        );
+        propagateContextChange(workInProgress, context, renderLanes);
       }
     }
   }
@@ -3086,7 +3069,7 @@ function updateContextConsumer(
   }
 
   prepareToReadContext(workInProgress, renderLanes);
-  const newValue = readContext(context, newProps.unstable_observedBits);
+  const newValue = readContext(context);
   let newChildren;
   if (__DEV__) {
     ReactCurrentOwner.current = workInProgress;
diff --git a/packages/react-reconciler/src/ReactFiberCacheComponent.new.js b/packages/react-reconciler/src/ReactFiberCacheComponent.new.js
index b5ae3ccc611a8..042a8b2efc098 100644
--- a/packages/react-reconciler/src/ReactFiberCacheComponent.new.js
+++ b/packages/react-reconciler/src/ReactFiberCacheComponent.new.js
@@ -37,7 +37,6 @@ export const CacheContext: ReactContext<Cache> = enableCache
       // We don't use Consumer/Provider for Cache components. So we'll cheat.
       Consumer: (null: any),
       Provider: (null: any),
-      _calculateChangedBits: null,
       // We'll initialize these at the root.
       _currentValue: (null: any),
       _currentValue2: (null: any),
diff --git a/packages/react-reconciler/src/ReactFiberCacheComponent.old.js b/packages/react-reconciler/src/ReactFiberCacheComponent.old.js
index 8882f7dbd2d48..2bc64254d3092 100644
--- a/packages/react-reconciler/src/ReactFiberCacheComponent.old.js
+++ b/packages/react-reconciler/src/ReactFiberCacheComponent.old.js
@@ -37,7 +37,6 @@ export const CacheContext: ReactContext<Cache> = enableCache
       // We don't use Consumer/Provider for Cache components. So we'll cheat.
       Consumer: (null: any),
       Provider: (null: any),
-      _calculateChangedBits: null,
       // We'll initialize these at the root.
       _currentValue: (null: any),
       _currentValue2: (null: any),
diff --git a/packages/react-reconciler/src/ReactFiberHooks.new.js b/packages/react-reconciler/src/ReactFiberHooks.new.js
index e7e5c3128beac..3c1c6c43081fc 100644
--- a/packages/react-reconciler/src/ReactFiberHooks.new.js
+++ b/packages/react-reconciler/src/ReactFiberHooks.new.js
@@ -2238,11 +2238,8 @@ if (__DEV__) {
   };
 
   HooksDispatcherOnMountInDEV = {
-    readContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
-      return readContext(context, observedBits);
+    readContext<T>(context: ReactContext<T>): T {
+      return readContext(context);
     },
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
       currentHookNameInDev = 'useCallback';
@@ -2250,13 +2247,10 @@ if (__DEV__) {
       checkDepsAreArrayDev(deps);
       return mountCallback(callback, deps);
     },
-    useContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    useContext<T>(context: ReactContext<T>): T {
       currentHookNameInDev = 'useContext';
       mountHookTypesDev();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useEffect(
       create: () => (() => void) | void,
@@ -2373,24 +2367,18 @@ if (__DEV__) {
   }
 
   HooksDispatcherOnMountWithHookTypesInDEV = {
-    readContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
-      return readContext(context, observedBits);
+    readContext<T>(context: ReactContext<T>): T {
+      return readContext(context);
     },
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
       currentHookNameInDev = 'useCallback';
       updateHookTypesDev();
       return mountCallback(callback, deps);
     },
-    useContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    useContext<T>(context: ReactContext<T>): T {
       currentHookNameInDev = 'useContext';
       updateHookTypesDev();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useEffect(
       create: () => (() => void) | void,
@@ -2503,24 +2491,18 @@ if (__DEV__) {
   }
 
   HooksDispatcherOnUpdateInDEV = {
-    readContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
-      return readContext(context, observedBits);
+    readContext<T>(context: ReactContext<T>): T {
+      return readContext(context);
     },
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
       currentHookNameInDev = 'useCallback';
       updateHookTypesDev();
       return updateCallback(callback, deps);
     },
-    useContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    useContext<T>(context: ReactContext<T>): T {
       currentHookNameInDev = 'useContext';
       updateHookTypesDev();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useEffect(
       create: () => (() => void) | void,
@@ -2633,11 +2615,8 @@ if (__DEV__) {
   }
 
   HooksDispatcherOnRerenderInDEV = {
-    readContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
-      return readContext(context, observedBits);
+    readContext<T>(context: ReactContext<T>): T {
+      return readContext(context);
     },
 
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
@@ -2645,13 +2624,10 @@ if (__DEV__) {
       updateHookTypesDev();
       return updateCallback(callback, deps);
     },
-    useContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    useContext<T>(context: ReactContext<T>): T {
       currentHookNameInDev = 'useContext';
       updateHookTypesDev();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useEffect(
       create: () => (() => void) | void,
@@ -2764,12 +2740,9 @@ if (__DEV__) {
   }
 
   InvalidNestedHooksDispatcherOnMountInDEV = {
-    readContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    readContext<T>(context: ReactContext<T>): T {
       warnInvalidContextAccess();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
       currentHookNameInDev = 'useCallback';
@@ -2777,14 +2750,11 @@ if (__DEV__) {
       mountHookTypesDev();
       return mountCallback(callback, deps);
     },
-    useContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    useContext<T>(context: ReactContext<T>): T {
       currentHookNameInDev = 'useContext';
       warnInvalidHookAccess();
       mountHookTypesDev();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useEffect(
       create: () => (() => void) | void,
@@ -2909,12 +2879,9 @@ if (__DEV__) {
   }
 
   InvalidNestedHooksDispatcherOnUpdateInDEV = {
-    readContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    readContext<T>(context: ReactContext<T>): T {
       warnInvalidContextAccess();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
       currentHookNameInDev = 'useCallback';
@@ -2922,14 +2889,11 @@ if (__DEV__) {
       updateHookTypesDev();
       return updateCallback(callback, deps);
     },
-    useContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    useContext<T>(context: ReactContext<T>): T {
       currentHookNameInDev = 'useContext';
       warnInvalidHookAccess();
       updateHookTypesDev();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useEffect(
       create: () => (() => void) | void,
@@ -3054,12 +3018,9 @@ if (__DEV__) {
   }
 
   InvalidNestedHooksDispatcherOnRerenderInDEV = {
-    readContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    readContext<T>(context: ReactContext<T>): T {
       warnInvalidContextAccess();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
 
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
@@ -3068,14 +3029,11 @@ if (__DEV__) {
       updateHookTypesDev();
       return updateCallback(callback, deps);
     },
-    useContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    useContext<T>(context: ReactContext<T>): T {
       currentHookNameInDev = 'useContext';
       warnInvalidHookAccess();
       updateHookTypesDev();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useEffect(
       create: () => (() => void) | void,
diff --git a/packages/react-reconciler/src/ReactFiberHooks.old.js b/packages/react-reconciler/src/ReactFiberHooks.old.js
index 55dca75656c35..2a0f70e1913b6 100644
--- a/packages/react-reconciler/src/ReactFiberHooks.old.js
+++ b/packages/react-reconciler/src/ReactFiberHooks.old.js
@@ -2238,11 +2238,8 @@ if (__DEV__) {
   };
 
   HooksDispatcherOnMountInDEV = {
-    readContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
-      return readContext(context, observedBits);
+    readContext<T>(context: ReactContext<T>): T {
+      return readContext(context);
     },
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
       currentHookNameInDev = 'useCallback';
@@ -2250,13 +2247,10 @@ if (__DEV__) {
       checkDepsAreArrayDev(deps);
       return mountCallback(callback, deps);
     },
-    useContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    useContext<T>(context: ReactContext<T>): T {
       currentHookNameInDev = 'useContext';
       mountHookTypesDev();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useEffect(
       create: () => (() => void) | void,
@@ -2373,24 +2367,18 @@ if (__DEV__) {
   }
 
   HooksDispatcherOnMountWithHookTypesInDEV = {
-    readContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
-      return readContext(context, observedBits);
+    readContext<T>(context: ReactContext<T>): T {
+      return readContext(context);
     },
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
       currentHookNameInDev = 'useCallback';
       updateHookTypesDev();
       return mountCallback(callback, deps);
     },
-    useContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    useContext<T>(context: ReactContext<T>): T {
       currentHookNameInDev = 'useContext';
       updateHookTypesDev();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useEffect(
       create: () => (() => void) | void,
@@ -2503,24 +2491,18 @@ if (__DEV__) {
   }
 
   HooksDispatcherOnUpdateInDEV = {
-    readContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
-      return readContext(context, observedBits);
+    readContext<T>(context: ReactContext<T>): T {
+      return readContext(context);
     },
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
       currentHookNameInDev = 'useCallback';
       updateHookTypesDev();
       return updateCallback(callback, deps);
     },
-    useContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    useContext<T>(context: ReactContext<T>): T {
       currentHookNameInDev = 'useContext';
       updateHookTypesDev();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useEffect(
       create: () => (() => void) | void,
@@ -2633,11 +2615,8 @@ if (__DEV__) {
   }
 
   HooksDispatcherOnRerenderInDEV = {
-    readContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
-      return readContext(context, observedBits);
+    readContext<T>(context: ReactContext<T>): T {
+      return readContext(context);
     },
 
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
@@ -2645,13 +2624,10 @@ if (__DEV__) {
       updateHookTypesDev();
       return updateCallback(callback, deps);
     },
-    useContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    useContext<T>(context: ReactContext<T>): T {
       currentHookNameInDev = 'useContext';
       updateHookTypesDev();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useEffect(
       create: () => (() => void) | void,
@@ -2764,12 +2740,9 @@ if (__DEV__) {
   }
 
   InvalidNestedHooksDispatcherOnMountInDEV = {
-    readContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    readContext<T>(context: ReactContext<T>): T {
       warnInvalidContextAccess();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
       currentHookNameInDev = 'useCallback';
@@ -2777,14 +2750,11 @@ if (__DEV__) {
       mountHookTypesDev();
       return mountCallback(callback, deps);
     },
-    useContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    useContext<T>(context: ReactContext<T>): T {
       currentHookNameInDev = 'useContext';
       warnInvalidHookAccess();
       mountHookTypesDev();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useEffect(
       create: () => (() => void) | void,
@@ -2909,12 +2879,9 @@ if (__DEV__) {
   }
 
   InvalidNestedHooksDispatcherOnUpdateInDEV = {
-    readContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    readContext<T>(context: ReactContext<T>): T {
       warnInvalidContextAccess();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
       currentHookNameInDev = 'useCallback';
@@ -2922,14 +2889,11 @@ if (__DEV__) {
       updateHookTypesDev();
       return updateCallback(callback, deps);
     },
-    useContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    useContext<T>(context: ReactContext<T>): T {
       currentHookNameInDev = 'useContext';
       warnInvalidHookAccess();
       updateHookTypesDev();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useEffect(
       create: () => (() => void) | void,
@@ -3054,12 +3018,9 @@ if (__DEV__) {
   }
 
   InvalidNestedHooksDispatcherOnRerenderInDEV = {
-    readContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    readContext<T>(context: ReactContext<T>): T {
       warnInvalidContextAccess();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
 
     useCallback<T>(callback: T, deps: Array<mixed> | void | null): T {
@@ -3068,14 +3029,11 @@ if (__DEV__) {
       updateHookTypesDev();
       return updateCallback(callback, deps);
     },
-    useContext<T>(
-      context: ReactContext<T>,
-      observedBits: void | number | boolean,
-    ): T {
+    useContext<T>(context: ReactContext<T>): T {
       currentHookNameInDev = 'useContext';
       warnInvalidHookAccess();
       updateHookTypesDev();
-      return readContext(context, observedBits);
+      return readContext(context);
     },
     useEffect(
       create: () => (() => void) | void,
diff --git a/packages/react-reconciler/src/ReactFiberNewContext.new.js b/packages/react-reconciler/src/ReactFiberNewContext.new.js
index 29a1eeef8cdd9..9d2484a783971 100644
--- a/packages/react-reconciler/src/ReactFiberNewContext.new.js
+++ b/packages/react-reconciler/src/ReactFiberNewContext.new.js
@@ -19,7 +19,6 @@ import type {SharedQueue} from './ReactUpdateQueue.new';
 
 import {isPrimaryRenderer} from './ReactFiberHostConfig';
 import {createCursor, push, pop} from './ReactFiberStack.new';
-import {MAX_SIGNED_31_BIT_INT} from './MaxInts';
 import {
   ContextProvider,
   ClassComponent,
@@ -58,7 +57,7 @@ if (__DEV__) {
 
 let currentlyRenderingFiber: Fiber | null = null;
 let lastContextDependency: ContextDependency<mixed> | null = null;
-let lastContextWithAllBitsObserved: ReactContext<any> | null = null;
+let lastFullyObservedContext: ReactContext<any> | null = null;
 
 let isDisallowedContextReadInDEV: boolean = false;
 
@@ -67,7 +66,7 @@ export function resetContextDependencies(): void {
   // cannot be called outside the render phase.
   currentlyRenderingFiber = null;
   lastContextDependency = null;
-  lastContextWithAllBitsObserved = null;
+  lastFullyObservedContext = null;
   if (__DEV__) {
     isDisallowedContextReadInDEV = false;
   }
@@ -140,33 +139,6 @@ export function popProvider(
   }
 }
 
-export function calculateChangedBits<T>(
-  context: ReactContext<T>,
-  newValue: T,
-  oldValue: T,
-) {
-  if (is(oldValue, newValue)) {
-    // No change
-    return 0;
-  } else {
-    const changedBits =
-      typeof context._calculateChangedBits === 'function'
-        ? context._calculateChangedBits(oldValue, newValue)
-        : MAX_SIGNED_31_BIT_INT;
-
-    if (__DEV__) {
-      if ((changedBits & MAX_SIGNED_31_BIT_INT) !== changedBits) {
-        console.error(
-          'calculateChangedBits: Expected the return value to be a ' +
-            '31-bit integer. Instead received: %s',
-          changedBits,
-        );
-      }
-    }
-    return changedBits | 0;
-  }
-}
-
 export function scheduleWorkOnParentPath(
   parent: Fiber | null,
   renderLanes: Lanes,
@@ -197,7 +169,6 @@ export function scheduleWorkOnParentPath(
 export function propagateContextChange<T>(
   workInProgress: Fiber,
   context: ReactContext<T>,
-  changedBits: number,
   renderLanes: Lanes,
 ): void {
   if (enableLazyContextPropagation) {
@@ -207,24 +178,18 @@ export function propagateContextChange<T>(
     const forcePropagateEntireTree = true;
     propagateContextChanges(
       workInProgress,
-      [context, changedBits],
+      [context],
       renderLanes,
       forcePropagateEntireTree,
     );
   } else {
-    propagateContextChange_eager(
-      workInProgress,
-      context,
-      changedBits,
-      renderLanes,
-    );
+    propagateContextChange_eager(workInProgress, context, renderLanes);
   }
 }
 
 function propagateContextChange_eager<T>(
   workInProgress: Fiber,
   context: ReactContext<T>,
-  changedBits: number,
   renderLanes: Lanes,
 ): void {
   // Only used by eager implemenation
@@ -247,10 +212,7 @@ function propagateContextChange_eager<T>(
       let dependency = list.firstContext;
       while (dependency !== null) {
         // Check if the context matches.
-        if (
-          dependency.context === context &&
-          (dependency.observedBits & changedBits) !== 0
-        ) {
+        if (dependency.context === context) {
           // Match! Schedule an update on this fiber.
           if (fiber.tag === ClassComponent) {
             // Schedule a force update on the work-in-progress.
@@ -382,15 +344,11 @@ function propagateContextChanges<T>(
         // Assigning these to constants to help Flow
         const dependency = dep;
         const consumer = fiber;
-        findContext: for (let i = 0; i < contexts.length; i += 2) {
+        findContext: for (let i = 0; i < contexts.length; i++) {
           const context: ReactContext<T> = contexts[i];
-          const changedBits: number = contexts[i + 1];
           // Check if the context matches.
           // TODO: Compare selected values to bail out early.
-          if (
-            dependency.context === context &&
-            (dependency.observedBits & changedBits) !== 0
-          ) {
+          if (dependency.context === context) {
             // Match! Schedule an update on this fiber.
 
             // In the lazy implemenation, don't mark a dirty flag on the
@@ -549,12 +507,11 @@ function propagateParentContextChanges(
 
         const oldValue = oldProps.value;
 
-        const changedBits = calculateChangedBits(context, newValue, oldValue);
-        if (changedBits !== 0) {
+        if (!is(newValue, oldValue)) {
           if (contexts !== null) {
-            contexts.push(context, changedBits);
+            contexts.push(context);
           } else {
-            contexts = [context, changedBits];
+            contexts = [context];
           }
         }
       }
@@ -625,7 +582,7 @@ export function prepareToReadContext(
 ): void {
   currentlyRenderingFiber = workInProgress;
   lastContextDependency = null;
-  lastContextWithAllBitsObserved = null;
+  lastFullyObservedContext = null;
 
   const dependencies = workInProgress.dependencies;
   if (dependencies !== null) {
@@ -646,10 +603,7 @@ export function prepareToReadContext(
   }
 }
 
-export function readContext<T>(
-  context: ReactContext<T>,
-  observedBits: void | number | boolean,
-): T {
+export function readContext<T>(context: ReactContext<T>): T {
   if (__DEV__) {
     // This warning would fire if you read context inside a Hook like useMemo.
     // Unlike the class check below, it's not enforced in production for perf.
@@ -667,26 +621,11 @@ export function readContext<T>(
     ? context._currentValue
     : context._currentValue2;
 
-  if (lastContextWithAllBitsObserved === context) {
+  if (lastFullyObservedContext === context) {
     // Nothing to do. We already observe everything in this context.
-  } else if (observedBits === false || observedBits === 0) {
-    // Do not observe any updates.
   } else {
-    let resolvedObservedBits; // Avoid deopting on observable arguments or heterogeneous types.
-    if (
-      typeof observedBits !== 'number' ||
-      observedBits === MAX_SIGNED_31_BIT_INT
-    ) {
-      // Observe all updates.
-      lastContextWithAllBitsObserved = ((context: any): ReactContext<mixed>);
-      resolvedObservedBits = MAX_SIGNED_31_BIT_INT;
-    } else {
-      resolvedObservedBits = observedBits;
-    }
-
     const contextItem = {
       context: ((context: any): ReactContext<mixed>),
-      observedBits: resolvedObservedBits,
       memoizedValue: value,
       next: null,
     };
diff --git a/packages/react-reconciler/src/ReactFiberNewContext.old.js b/packages/react-reconciler/src/ReactFiberNewContext.old.js
index 0e6ed587b8ddb..c2a1600650119 100644
--- a/packages/react-reconciler/src/ReactFiberNewContext.old.js
+++ b/packages/react-reconciler/src/ReactFiberNewContext.old.js
@@ -19,7 +19,6 @@ import type {SharedQueue} from './ReactUpdateQueue.old';
 
 import {isPrimaryRenderer} from './ReactFiberHostConfig';
 import {createCursor, push, pop} from './ReactFiberStack.old';
-import {MAX_SIGNED_31_BIT_INT} from './MaxInts';
 import {
   ContextProvider,
   ClassComponent,
@@ -58,7 +57,7 @@ if (__DEV__) {
 
 let currentlyRenderingFiber: Fiber | null = null;
 let lastContextDependency: ContextDependency<mixed> | null = null;
-let lastContextWithAllBitsObserved: ReactContext<any> | null = null;
+let lastFullyObservedContext: ReactContext<any> | null = null;
 
 let isDisallowedContextReadInDEV: boolean = false;
 
@@ -67,7 +66,7 @@ export function resetContextDependencies(): void {
   // cannot be called outside the render phase.
   currentlyRenderingFiber = null;
   lastContextDependency = null;
-  lastContextWithAllBitsObserved = null;
+  lastFullyObservedContext = null;
   if (__DEV__) {
     isDisallowedContextReadInDEV = false;
   }
@@ -140,33 +139,6 @@ export function popProvider(
   }
 }
 
-export function calculateChangedBits<T>(
-  context: ReactContext<T>,
-  newValue: T,
-  oldValue: T,
-) {
-  if (is(oldValue, newValue)) {
-    // No change
-    return 0;
-  } else {
-    const changedBits =
-      typeof context._calculateChangedBits === 'function'
-        ? context._calculateChangedBits(oldValue, newValue)
-        : MAX_SIGNED_31_BIT_INT;
-
-    if (__DEV__) {
-      if ((changedBits & MAX_SIGNED_31_BIT_INT) !== changedBits) {
-        console.error(
-          'calculateChangedBits: Expected the return value to be a ' +
-            '31-bit integer. Instead received: %s',
-          changedBits,
-        );
-      }
-    }
-    return changedBits | 0;
-  }
-}
-
 export function scheduleWorkOnParentPath(
   parent: Fiber | null,
   renderLanes: Lanes,
@@ -197,7 +169,6 @@ export function scheduleWorkOnParentPath(
 export function propagateContextChange<T>(
   workInProgress: Fiber,
   context: ReactContext<T>,
-  changedBits: number,
   renderLanes: Lanes,
 ): void {
   if (enableLazyContextPropagation) {
@@ -207,24 +178,18 @@ export function propagateContextChange<T>(
     const forcePropagateEntireTree = true;
     propagateContextChanges(
       workInProgress,
-      [context, changedBits],
+      [context],
       renderLanes,
       forcePropagateEntireTree,
     );
   } else {
-    propagateContextChange_eager(
-      workInProgress,
-      context,
-      changedBits,
-      renderLanes,
-    );
+    propagateContextChange_eager(workInProgress, context, renderLanes);
   }
 }
 
 function propagateContextChange_eager<T>(
   workInProgress: Fiber,
   context: ReactContext<T>,
-  changedBits: number,
   renderLanes: Lanes,
 ): void {
   // Only used by eager implemenation
@@ -247,10 +212,7 @@ function propagateContextChange_eager<T>(
       let dependency = list.firstContext;
       while (dependency !== null) {
         // Check if the context matches.
-        if (
-          dependency.context === context &&
-          (dependency.observedBits & changedBits) !== 0
-        ) {
+        if (dependency.context === context) {
           // Match! Schedule an update on this fiber.
           if (fiber.tag === ClassComponent) {
             // Schedule a force update on the work-in-progress.
@@ -382,15 +344,11 @@ function propagateContextChanges<T>(
         // Assigning these to constants to help Flow
         const dependency = dep;
         const consumer = fiber;
-        findContext: for (let i = 0; i < contexts.length; i += 2) {
+        findContext: for (let i = 0; i < contexts.length; i++) {
           const context: ReactContext<T> = contexts[i];
-          const changedBits: number = contexts[i + 1];
           // Check if the context matches.
           // TODO: Compare selected values to bail out early.
-          if (
-            dependency.context === context &&
-            (dependency.observedBits & changedBits) !== 0
-          ) {
+          if (dependency.context === context) {
             // Match! Schedule an update on this fiber.
 
             // In the lazy implemenation, don't mark a dirty flag on the
@@ -549,12 +507,11 @@ function propagateParentContextChanges(
 
         const oldValue = oldProps.value;
 
-        const changedBits = calculateChangedBits(context, newValue, oldValue);
-        if (changedBits !== 0) {
+        if (!is(newValue, oldValue)) {
           if (contexts !== null) {
-            contexts.push(context, changedBits);
+            contexts.push(context);
           } else {
-            contexts = [context, changedBits];
+            contexts = [context];
           }
         }
       }
@@ -625,7 +582,7 @@ export function prepareToReadContext(
 ): void {
   currentlyRenderingFiber = workInProgress;
   lastContextDependency = null;
-  lastContextWithAllBitsObserved = null;
+  lastFullyObservedContext = null;
 
   const dependencies = workInProgress.dependencies;
   if (dependencies !== null) {
@@ -646,10 +603,7 @@ export function prepareToReadContext(
   }
 }
 
-export function readContext<T>(
-  context: ReactContext<T>,
-  observedBits: void | number | boolean,
-): T {
+export function readContext<T>(context: ReactContext<T>): T {
   if (__DEV__) {
     // This warning would fire if you read context inside a Hook like useMemo.
     // Unlike the class check below, it's not enforced in production for perf.
@@ -667,26 +621,11 @@ export function readContext<T>(
     ? context._currentValue
     : context._currentValue2;
 
-  if (lastContextWithAllBitsObserved === context) {
+  if (lastFullyObservedContext === context) {
     // Nothing to do. We already observe everything in this context.
-  } else if (observedBits === false || observedBits === 0) {
-    // Do not observe any updates.
   } else {
-    let resolvedObservedBits; // Avoid deopting on observable arguments or heterogeneous types.
-    if (
-      typeof observedBits !== 'number' ||
-      observedBits === MAX_SIGNED_31_BIT_INT
-    ) {
-      // Observe all updates.
-      lastContextWithAllBitsObserved = ((context: any): ReactContext<mixed>);
-      resolvedObservedBits = MAX_SIGNED_31_BIT_INT;
-    } else {
-      resolvedObservedBits = observedBits;
-    }
-
     const contextItem = {
       context: ((context: any): ReactContext<mixed>),
-      observedBits: resolvedObservedBits,
       memoizedValue: value,
       next: null,
     };
diff --git a/packages/react-reconciler/src/ReactInternalTypes.js b/packages/react-reconciler/src/ReactInternalTypes.js
index b1764bed5ac34..e5fd43e6f416e 100644
--- a/packages/react-reconciler/src/ReactInternalTypes.js
+++ b/packages/react-reconciler/src/ReactInternalTypes.js
@@ -49,7 +49,6 @@ export type ReactPriorityLevel = 99 | 98 | 97 | 96 | 95 | 90;
 
 export type ContextDependency<T> = {
   context: ReactContext<T>,
-  observedBits: number,
   next: ContextDependency<mixed> | null,
   memoizedValue: T,
   ...
@@ -281,20 +280,14 @@ type Dispatch<A> = A => void;
 
 export type Dispatcher = {|
   getCacheForType?: <T>(resourceType: () => T) => T,
-  readContext<T>(
-    context: ReactContext<T>,
-    observedBits: void | number | boolean,
-  ): T,
+  readContext<T>(context: ReactContext<T>): T,
   useState<S>(initialState: (() => S) | S): [S, Dispatch<BasicStateAction<S>>],
   useReducer<S, I, A>(
     reducer: (S, A) => S,
     initialArg: I,
     init?: (I) => S,
   ): [S, Dispatch<A>],
-  useContext<T>(
-    context: ReactContext<T>,
-    observedBits: void | number | boolean,
-  ): T,
+  useContext<T>(context: ReactContext<T>): T,
   useRef<T>(initialValue: T): {|current: T|},
   useEffect(
     create: () => (() => void) | void,
diff --git a/packages/react-reconciler/src/__tests__/ReactNewContext-test.js b/packages/react-reconciler/src/__tests__/ReactNewContext-test.js
index 43c1e0033c2f3..4f64972715ac4 100644
--- a/packages/react-reconciler/src/__tests__/ReactNewContext-test.js
+++ b/packages/react-reconciler/src/__tests__/ReactNewContext-test.js
@@ -35,11 +35,11 @@ describe('ReactNewContext', () => {
     return {type: 'span', children: [], prop, hidden: false};
   }
 
-  function readContext(Context, observedBits) {
+  function readContext(Context) {
     const dispatcher =
       React.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED
         .ReactCurrentDispatcher.current;
-    return dispatcher.readContext(Context, observedBits);
+    return dispatcher.readContext(Context);
   }
 
   // Note: This is based on a similar component we use in www. We can delete
@@ -62,48 +62,21 @@ describe('ReactNewContext', () => {
     'useContext inside function component',
     Context =>
       function Consumer(props) {
-        const observedBits = props.unstable_observedBits;
-        let contextValue;
-        expect(() => {
-          contextValue = useContext(Context, observedBits);
-        }).toErrorDev(
-          observedBits !== undefined
-            ? 'useContext() second argument is reserved for future use in React. ' +
-                `Passing it is not supported. You passed: ${observedBits}.`
-            : [],
-        );
+        const contextValue = useContext(Context);
         const render = props.children;
         return render(contextValue);
       },
   );
   sharedContextTests('useContext inside forwardRef component', Context =>
     React.forwardRef(function Consumer(props, ref) {
-      const observedBits = props.unstable_observedBits;
-      let contextValue;
-      expect(() => {
-        contextValue = useContext(Context, observedBits);
-      }).toErrorDev(
-        observedBits !== undefined
-          ? 'useContext() second argument is reserved for future use in React. ' +
-              `Passing it is not supported. You passed: ${observedBits}.`
-          : [],
-      );
+      const contextValue = useContext(Context);
       const render = props.children;
       return render(contextValue);
     }),
   );
   sharedContextTests('useContext inside memoized function component', Context =>
     React.memo(function Consumer(props) {
-      const observedBits = props.unstable_observedBits;
-      let contextValue;
-      expect(() => {
-        contextValue = useContext(Context, observedBits);
-      }).toErrorDev(
-        observedBits !== undefined
-          ? 'useContext() second argument is reserved for future use in React. ' +
-              `Passing it is not supported. You passed: ${observedBits}.`
-          : [],
-      );
+      const contextValue = useContext(Context);
       const render = props.children;
       return render(contextValue);
     }),
@@ -113,8 +86,7 @@ describe('ReactNewContext', () => {
     Context =>
       class Consumer extends React.Component {
         render() {
-          const observedBits = this.props.unstable_observedBits;
-          const contextValue = readContext(Context, observedBits);
+          const contextValue = readContext(Context);
           const render = this.props.children;
           return render(contextValue);
         }
@@ -125,8 +97,7 @@ describe('ReactNewContext', () => {
     Context =>
       class Consumer extends React.PureComponent {
         render() {
-          const observedBits = this.props.unstable_observedBits;
-          const contextValue = readContext(Context, observedBits);
+          const contextValue = readContext(Context);
           const render = this.props.children;
           return render(contextValue);
         }
@@ -590,227 +561,6 @@ describe('ReactNewContext', () => {
         ]);
       });
 
-      it('can skip consumers with bitmask', () => {
-        const Context = React.createContext({foo: 0, bar: 0}, (a, b) => {
-          let result = 0;
-          if (a.foo !== b.foo) {
-            result |= 0b01;
-          }
-          if (a.bar !== b.bar) {
-            result |= 0b10;
-          }
-          return result;
-        });
-        const Consumer = getConsumer(Context);
-
-        function Provider(props) {
-          return (
-            <Context.Provider value={{foo: props.foo, bar: props.bar}}>
-              {props.children}
-            </Context.Provider>
-          );
-        }
-
-        function Foo() {
-          return (
-            <Consumer unstable_observedBits={0b01}>
-              {value => {
-                Scheduler.unstable_yieldValue('Foo');
-                return <span prop={'Foo: ' + value.foo} />;
-              }}
-            </Consumer>
-          );
-        }
-
-        function Bar() {
-          return (
-            <Consumer unstable_observedBits={0b10}>
-              {value => {
-                Scheduler.unstable_yieldValue('Bar');
-                return <span prop={'Bar: ' + value.bar} />;
-              }}
-            </Consumer>
-          );
-        }
-
-        class Indirection extends React.Component {
-          shouldComponentUpdate() {
-            return false;
-          }
-          render() {
-            return this.props.children;
-          }
-        }
-
-        function App(props) {
-          return (
-            <Provider foo={props.foo} bar={props.bar}>
-              <Indirection>
-                <Indirection>
-                  <Foo />
-                </Indirection>
-                <Indirection>
-                  <Bar />
-                </Indirection>
-              </Indirection>
-            </Provider>
-          );
-        }
-
-        ReactNoop.render(<App foo={1} bar={1} />);
-        expect(Scheduler).toFlushAndYield(['Foo', 'Bar']);
-        expect(ReactNoop.getChildren()).toEqual([
-          span('Foo: 1'),
-          span('Bar: 1'),
-        ]);
-
-        // Update only foo
-        ReactNoop.render(<App foo={2} bar={1} />);
-        expect(Scheduler).toFlushAndYield(['Foo']);
-        expect(ReactNoop.getChildren()).toEqual([
-          span('Foo: 2'),
-          span('Bar: 1'),
-        ]);
-
-        // Update only bar
-        ReactNoop.render(<App foo={2} bar={2} />);
-        expect(Scheduler).toFlushAndYield(['Bar']);
-        expect(ReactNoop.getChildren()).toEqual([
-          span('Foo: 2'),
-          span('Bar: 2'),
-        ]);
-
-        // Update both
-        ReactNoop.render(<App foo={3} bar={3} />);
-        expect(Scheduler).toFlushAndYield(['Foo', 'Bar']);
-        expect(ReactNoop.getChildren()).toEqual([
-          span('Foo: 3'),
-          span('Bar: 3'),
-        ]);
-      });
-
-      // @gate !enableLazyContextPropagation
-      it('can skip parents with bitmask bailout while updating their children', () => {
-        const Context = React.createContext({foo: 0, bar: 0}, (a, b) => {
-          let result = 0;
-          if (a.foo !== b.foo) {
-            result |= 0b01;
-          }
-          if (a.bar !== b.bar) {
-            result |= 0b10;
-          }
-          return result;
-        });
-        const Consumer = getConsumer(Context);
-
-        function Provider(props) {
-          return (
-            <Context.Provider value={{foo: props.foo, bar: props.bar}}>
-              {props.children}
-            </Context.Provider>
-          );
-        }
-
-        function Foo(props) {
-          return (
-            <Consumer unstable_observedBits={0b01}>
-              {value => {
-                Scheduler.unstable_yieldValue('Foo');
-                return (
-                  <>
-                    <span prop={'Foo: ' + value.foo} />
-                    {props.children && props.children()}
-                  </>
-                );
-              }}
-            </Consumer>
-          );
-        }
-
-        function Bar(props) {
-          return (
-            <Consumer unstable_observedBits={0b10}>
-              {value => {
-                Scheduler.unstable_yieldValue('Bar');
-                return (
-                  <>
-                    <span prop={'Bar: ' + value.bar} />
-                    {props.children && props.children()}
-                  </>
-                );
-              }}
-            </Consumer>
-          );
-        }
-
-        class Indirection extends React.Component {
-          shouldComponentUpdate() {
-            return false;
-          }
-          render() {
-            return this.props.children;
-          }
-        }
-
-        function App(props) {
-          return (
-            <Provider foo={props.foo} bar={props.bar}>
-              <Indirection>
-                <Foo>
-                  {/* Use a render prop so we don't test constant elements. */}
-                  {() => (
-                    <Indirection>
-                      <Bar>
-                        {() => (
-                          <Indirection>
-                            <Foo />
-                          </Indirection>
-                        )}
-                      </Bar>
-                    </Indirection>
-                  )}
-                </Foo>
-              </Indirection>
-            </Provider>
-          );
-        }
-
-        ReactNoop.render(<App foo={1} bar={1} />);
-        expect(Scheduler).toFlushAndYield(['Foo', 'Bar', 'Foo']);
-        expect(ReactNoop.getChildren()).toEqual([
-          span('Foo: 1'),
-          span('Bar: 1'),
-          span('Foo: 1'),
-        ]);
-
-        // Update only foo
-        ReactNoop.render(<App foo={2} bar={1} />);
-        expect(Scheduler).toFlushAndYield(['Foo', 'Foo']);
-        expect(ReactNoop.getChildren()).toEqual([
-          span('Foo: 2'),
-          span('Bar: 1'),
-          span('Foo: 2'),
-        ]);
-
-        // Update only bar
-        ReactNoop.render(<App foo={2} bar={2} />);
-        expect(Scheduler).toFlushAndYield(['Bar']);
-        expect(ReactNoop.getChildren()).toEqual([
-          span('Foo: 2'),
-          span('Bar: 2'),
-          span('Foo: 2'),
-        ]);
-
-        // Update both
-        ReactNoop.render(<App foo={3} bar={3} />);
-        expect(Scheduler).toFlushAndYield(['Foo', 'Bar', 'Foo']);
-        expect(ReactNoop.getChildren()).toEqual([
-          span('Foo: 3'),
-          span('Bar: 3'),
-          span('Foo: 3'),
-        ]);
-      });
-
       it("does not re-render if there's an update in a child", () => {
         const Context = React.createContext(0);
         const Consumer = getConsumer(Context);
@@ -1063,30 +813,6 @@ describe('ReactNewContext', () => {
   }
 
   describe('Context.Provider', () => {
-    it('warns if calculateChangedBits returns larger than a 31-bit integer', () => {
-      const Context = React.createContext(
-        0,
-        (a, b) => Math.pow(2, 32) - 1, // Return 32 bit int
-      );
-
-      function App(props) {
-        return <Context.Provider value={props.value} />;
-      }
-
-      ReactNoop.render(<App value={1} />);
-      expect(Scheduler).toFlushWithoutYielding();
-
-      // Update
-      ReactNoop.render(<App value={2} />);
-
-      if (gate(flags => !flags.enableLazyContextPropagation)) {
-        expect(() => expect(Scheduler).toFlushWithoutYielding()).toErrorDev(
-          'calculateChangedBits: Expected the return value to be a 31-bit ' +
-            'integer. Instead received: 4294967295',
-        );
-      }
-    });
-
     it('warns if no value prop provided', () => {
       const Context = React.createContext();
 
@@ -1355,6 +1081,9 @@ describe('ReactNewContext', () => {
   });
 
   describe('readContext', () => {
+    // Unstable changedBits API was removed. Port this test to context selectors
+    // once that exists.
+    // @gate FIXME
     it('can read the same context multiple times in the same function', () => {
       const Context = React.createContext({foo: 0, bar: 0, baz: 0}, (a, b) => {
         let result = 0;
@@ -1517,22 +1246,6 @@ describe('ReactNewContext', () => {
   });
 
   describe('useContext', () => {
-    it('warns on array.map(useContext)', () => {
-      const Context = React.createContext(0);
-      function Foo() {
-        return [Context].map(useContext);
-      }
-      ReactNoop.render(<Foo />);
-      expect(() => expect(Scheduler).toFlushWithoutYielding()).toErrorDev(
-        'useContext() second argument is reserved for future ' +
-          'use in React. Passing it is not supported. ' +
-          'You passed: 0.\n\n' +
-          'Did you call array.map(useContext)? ' +
-          'Calling Hooks inside a loop is not supported. ' +
-          'Learn more at https://reactjs.org/link/rules-of-hooks',
-      );
-    });
-
     it('throws when used in a class component', () => {
       const Context = React.createContext(0);
       class Foo extends React.Component {
diff --git a/packages/react/src/ReactContext.js b/packages/react/src/ReactContext.js
index a3c4243dd0116..41065c13ef067 100644
--- a/packages/react/src/ReactContext.js
+++ b/packages/react/src/ReactContext.js
@@ -11,30 +11,12 @@ import {REACT_PROVIDER_TYPE, REACT_CONTEXT_TYPE} from 'shared/ReactSymbols';
 
 import type {ReactContext} from 'shared/ReactTypes';
 
-export function createContext<T>(
-  defaultValue: T,
-  calculateChangedBits: ?(a: T, b: T) => number,
-): ReactContext<T> {
-  if (calculateChangedBits === undefined) {
-    calculateChangedBits = null;
-  } else {
-    if (__DEV__) {
-      if (
-        calculateChangedBits !== null &&
-        typeof calculateChangedBits !== 'function'
-      ) {
-        console.error(
-          'createContext: Expected the optional second argument to be a ' +
-            'function. Instead received: %s',
-          calculateChangedBits,
-        );
-      }
-    }
-  }
+export function createContext<T>(defaultValue: T): ReactContext<T> {
+  // TODO: Second argument used to be an optional `calculateChangedBits`
+  // function. Warn to reserve for future use?
 
   const context: ReactContext<T> = {
     $$typeof: REACT_CONTEXT_TYPE,
-    _calculateChangedBits: calculateChangedBits,
     // As a workaround to support multiple concurrent renderers, we categorize
     // some renderers as primary and others as secondary. We only expect
     // there to be two concurrent renderers at most: React Native (primary) and
@@ -66,7 +48,6 @@ export function createContext<T>(
     const Consumer = {
       $$typeof: REACT_CONTEXT_TYPE,
       _context: context,
-      _calculateChangedBits: context._calculateChangedBits,
     };
     // $FlowFixMe: Flow complains about not setting a value, which is intentional here
     Object.defineProperties(Consumer, {
diff --git a/packages/react/src/ReactHooks.js b/packages/react/src/ReactHooks.js
index d397d8f789f0a..18920be2c8df4 100644
--- a/packages/react/src/ReactHooks.js
+++ b/packages/react/src/ReactHooks.js
@@ -47,26 +47,9 @@ export function getCacheForType<T>(resourceType: () => T): T {
   return dispatcher.getCacheForType(resourceType);
 }
 
-export function useContext<T>(
-  Context: ReactContext<T>,
-  unstable_observedBits: number | boolean | void,
-): T {
+export function useContext<T>(Context: ReactContext<T>): T {
   const dispatcher = resolveDispatcher();
   if (__DEV__) {
-    if (unstable_observedBits !== undefined) {
-      console.error(
-        'useContext() second argument is reserved for future ' +
-          'use in React. Passing it is not supported. ' +
-          'You passed: %s.%s',
-        unstable_observedBits,
-        typeof unstable_observedBits === 'number' && Array.isArray(arguments[2])
-          ? '\n\nDid you call array.map(useContext)? ' +
-              'Calling Hooks inside a loop is not supported. ' +
-              'Learn more at https://reactjs.org/link/rules-of-hooks'
-          : '',
-      );
-    }
-
     // TODO: add a more generic warning for invalid values.
     if ((Context: any)._context !== undefined) {
       const realContext = (Context: any)._context;
@@ -85,7 +68,7 @@ export function useContext<T>(
       }
     }
   }
-  return dispatcher.useContext(Context, unstable_observedBits);
+  return dispatcher.useContext(Context);
 }
 
 export function useState<S>(
diff --git a/packages/shared/ReactTypes.js b/packages/shared/ReactTypes.js
index dc31b998ea31c..55061fe8b9b82 100644
--- a/packages/shared/ReactTypes.js
+++ b/packages/shared/ReactTypes.js
@@ -59,7 +59,6 @@ export type ReactContext<T> = {
   $$typeof: Symbol | number,
   Consumer: ReactContext<T>,
   Provider: ReactProviderType<T>,
-  _calculateChangedBits: ((a: T, b: T) => number) | null,
   _currentValue: T,
   _currentValue2: T,
   _threadCount: number,