diff --git a/packages/react-dom-bindings/src/client/CSSPropertyOperations.js b/packages/react-dom-bindings/src/client/CSSPropertyOperations.js
index 521f4c67fc66b..9c07945aecff9 100644
--- a/packages/react-dom-bindings/src/client/CSSPropertyOperations.js
+++ b/packages/react-dom-bindings/src/client/CSSPropertyOperations.js
@@ -11,7 +11,6 @@ import hyphenateStyleName from '../shared/hyphenateStyleName';
 import warnValidStyle from '../shared/warnValidStyle';
 import isUnitlessNumber from '../shared/isUnitlessNumber';
 import {checkCSSPropertyStringCoercion} from 'shared/CheckStringCoercion';
-import {diffInCommitPhase} from 'shared/ReactFeatureFlags';
 
 /**
  * Operations for dealing with CSS properties.
@@ -65,42 +64,6 @@ export function createDangerousStringForStyles(styles) {
   }
 }
 
-function setValueForStyle(style, styleName, value) {
-  const isCustomProperty = styleName.indexOf('--') === 0;
-  if (__DEV__) {
-    if (!isCustomProperty) {
-      warnValidStyle(styleName, value);
-    }
-  }
-
-  if (value == null || typeof value === 'boolean' || value === '') {
-    if (isCustomProperty) {
-      style.setProperty(styleName, '');
-    } else if (styleName === 'float') {
-      style.cssFloat = '';
-    } else {
-      style[styleName] = '';
-    }
-  } else if (isCustomProperty) {
-    style.setProperty(styleName, value);
-  } else if (
-    typeof value === 'number' &&
-    value !== 0 &&
-    !isUnitlessNumber(styleName)
-  ) {
-    style[styleName] = value + 'px'; // Presumes implicit 'px' suffix for unitless numbers
-  } else {
-    if (styleName === 'float') {
-      style.cssFloat = value;
-    } else {
-      if (__DEV__) {
-        checkCSSPropertyStringCoercion(value, styleName);
-      }
-      style[styleName] = ('' + value).trim();
-    }
-  }
-}
-
 /**
  * Sets the value for multiple styles on a node.  If a value is specified as
  * '' (empty string), the corresponding style property will be unset.
@@ -108,7 +71,7 @@ function setValueForStyle(style, styleName, value) {
  * @param {DOMElement} node
  * @param {object} styles
  */
-export function setValueForStyles(node, styles, prevStyles) {
+export function setValueForStyles(node, styles) {
   if (styles != null && typeof styles !== 'object') {
     throw new Error(
       'The `style` prop expects a mapping from style properties to values, ' +
@@ -125,39 +88,42 @@ export function setValueForStyles(node, styles, prevStyles) {
   }
 
   const style = node.style;
-
-  if (diffInCommitPhase && prevStyles != null) {
-    if (__DEV__) {
-      validateShorthandPropertyCollisionInDev(prevStyles, styles);
+  for (const styleName in styles) {
+    if (!styles.hasOwnProperty(styleName)) {
+      continue;
     }
-
-    for (const styleName in prevStyles) {
-      if (
-        prevStyles.hasOwnProperty(styleName) &&
-        (styles == null || !styles.hasOwnProperty(styleName))
-      ) {
-        // Clear style
-        const isCustomProperty = styleName.indexOf('--') === 0;
-        if (isCustomProperty) {
-          style.setProperty(styleName, '');
-        } else if (styleName === 'float') {
-          style.cssFloat = '';
-        } else {
-          style[styleName] = '';
-        }
+    const value = styles[styleName];
+    const isCustomProperty = styleName.indexOf('--') === 0;
+    if (__DEV__) {
+      if (!isCustomProperty) {
+        warnValidStyle(styleName, value);
       }
     }
-    for (const styleName in styles) {
-      const value = styles[styleName];
-      if (styles.hasOwnProperty(styleName) && prevStyles[styleName] !== value) {
-        setValueForStyle(style, styleName, value);
+
+    if (value == null || typeof value === 'boolean' || value === '') {
+      if (isCustomProperty) {
+        style.setProperty(styleName, '');
+      } else if (styleName === 'float') {
+        style.cssFloat = '';
+      } else {
+        style[styleName] = '';
       }
-    }
-  } else {
-    for (const styleName in styles) {
-      if (styles.hasOwnProperty(styleName)) {
-        const value = styles[styleName];
-        setValueForStyle(style, styleName, value);
+    } else if (isCustomProperty) {
+      style.setProperty(styleName, value);
+    } else if (
+      typeof value === 'number' &&
+      value !== 0 &&
+      !isUnitlessNumber(styleName)
+    ) {
+      style[styleName] = value + 'px'; // Presumes implicit 'px' suffix for unitless numbers
+    } else {
+      if (styleName === 'float') {
+        style.cssFloat = value;
+      } else {
+        if (__DEV__) {
+          checkCSSPropertyStringCoercion(value, styleName);
+        }
+        style[styleName] = ('' + value).trim();
       }
     }
   }
@@ -201,7 +167,7 @@ function expandShorthandMap(styles) {
  *   becomes .style.fontVariant = ''
  */
 export function validateShorthandPropertyCollisionInDev(
-  prevStyles,
+  styleUpdates,
   nextStyles,
 ) {
   if (__DEV__) {
@@ -209,30 +175,7 @@ export function validateShorthandPropertyCollisionInDev(
       return;
     }
 
-    // Compute the diff as it would happen elsewhere.
-    const expandedUpdates = {};
-    if (prevStyles) {
-      for (const key in prevStyles) {
-        if (prevStyles.hasOwnProperty(key) && !nextStyles.hasOwnProperty(key)) {
-          const longhands = shorthandToLonghand[key] || [key];
-          for (let i = 0; i < longhands.length; i++) {
-            expandedUpdates[longhands[i]] = key;
-          }
-        }
-      }
-    }
-    for (const key in nextStyles) {
-      if (
-        nextStyles.hasOwnProperty(key) &&
-        (!prevStyles || prevStyles[key] !== nextStyles[key])
-      ) {
-        const longhands = shorthandToLonghand[key] || [key];
-        for (let i = 0; i < longhands.length; i++) {
-          expandedUpdates[longhands[i]] = key;
-        }
-      }
-    }
-
+    const expandedUpdates = expandShorthandMap(styleUpdates);
     const expandedStyles = expandShorthandMap(nextStyles);
     const warnedAbout = {};
     for (const key in expandedUpdates) {
@@ -250,7 +193,7 @@ export function validateShorthandPropertyCollisionInDev(
             "avoid this, don't mix shorthand and non-shorthand properties " +
             'for the same value; instead, replace the shorthand with ' +
             'separate values.',
-          isValueEmpty(nextStyles[originalKey]) ? 'Removing' : 'Updating',
+          isValueEmpty(styleUpdates[originalKey]) ? 'Removing' : 'Updating',
           originalKey,
           correctOriginalKey,
         );
diff --git a/packages/react-dom-bindings/src/client/ReactDOMComponent.js b/packages/react-dom-bindings/src/client/ReactDOMComponent.js
index e9398cf076f61..4e1ecda7857ff 100644
--- a/packages/react-dom-bindings/src/client/ReactDOMComponent.js
+++ b/packages/react-dom-bindings/src/client/ReactDOMComponent.js
@@ -69,7 +69,6 @@ import {
   disableIEWorkarounds,
   enableTrustedTypesIntegration,
   enableFilterEmptyStringAttributesDOM,
-  diffInCommitPhase,
 } from 'shared/ReactFeatureFlags';
 import {
   mediaEventTypes,
@@ -274,7 +273,6 @@ function setProp(
   key: string,
   value: mixed,
   props: any,
-  prevValue: mixed,
 ): void {
   switch (key) {
     case 'children': {
@@ -316,7 +314,7 @@ function setProp(
       break;
     }
     case 'style': {
-      setValueForStyles(domElement, value, prevValue);
+      setValueForStyles(domElement, value);
       break;
     }
     // These attributes accept URLs. These must not allow javascript: URLS.
@@ -657,21 +655,6 @@ function setProp(
       );
       break;
     // Properties that should not be allowed on custom elements.
-    case 'is': {
-      if (__DEV__) {
-        if (prevValue != null) {
-          console.error(
-            'Cannot update the "is" prop after it has been initialized.',
-          );
-        }
-      }
-      // TODO: We shouldn't actually set this attribute, because we've already
-      // passed it to createElement. We don't also need the attribute.
-      // However, our tests currently query for it so it's plausible someone
-      // else does too so it's break.
-      setValueForAttribute(domElement, 'is', value);
-      break;
-    }
     case 'innerText':
     case 'textContent':
       if (enableCustomElementPropertySupport) {
@@ -706,11 +689,10 @@ function setPropOnCustomElement(
   key: string,
   value: mixed,
   props: any,
-  prevValue: mixed,
 ): void {
   switch (key) {
     case 'style': {
-      setValueForStyles(domElement, value, prevValue);
+      setValueForStyles(domElement, value);
       break;
     }
     case 'dangerouslySetInnerHTML': {
@@ -877,7 +859,7 @@ export function setInitialProperties(
           }
           // defaultChecked and defaultValue are ignored by setProp
           default: {
-            setProp(domElement, tag, propKey, propValue, props, null);
+            setProp(domElement, tag, propKey, propValue, props);
           }
         }
       }
@@ -910,7 +892,7 @@ export function setInitialProperties(
           }
           // defaultValue are ignored by setProp
           default: {
-            setProp(domElement, tag, propKey, propValue, props, null);
+            setProp(domElement, tag, propKey, propValue, props);
           }
         }
       }
@@ -1065,7 +1047,7 @@ export function setInitialProperties(
           }
           // defaultChecked and defaultValue are ignored by setProp
           default: {
-            setProp(domElement, tag, propKey, propValue, props, null);
+            setProp(domElement, tag, propKey, propValue, props);
           }
         }
       }
@@ -1081,14 +1063,7 @@ export function setInitialProperties(
           if (propValue == null) {
             continue;
           }
-          setPropOnCustomElement(
-            domElement,
-            tag,
-            propKey,
-            propValue,
-            props,
-            null,
-          );
+          setPropOnCustomElement(domElement, tag, propKey, propValue, props);
         }
         return;
       }
@@ -1103,7 +1078,7 @@ export function setInitialProperties(
     if (propValue == null) {
       continue;
     }
-    setProp(domElement, tag, propKey, propValue, props, null);
+    setProp(domElement, tag, propKey, propValue, props);
   }
 }
 
@@ -1213,428 +1188,15 @@ export function diffProperties(
   }
   if (styleUpdates) {
     if (__DEV__) {
-      validateShorthandPropertyCollisionInDev(lastProps.style, nextProps.style);
+      validateShorthandPropertyCollisionInDev(styleUpdates, nextProps.style);
     }
     (updatePayload = updatePayload || []).push('style', styleUpdates);
   }
   return updatePayload;
 }
 
-export function updateProperties(
-  domElement: Element,
-  tag: string,
-  lastProps: Object,
-  nextProps: Object,
-): void {
-  if (__DEV__) {
-    validatePropertiesInDevelopment(tag, nextProps);
-  }
-
-  switch (tag) {
-    case 'div':
-    case 'span':
-    case 'svg':
-    case 'path':
-    case 'a':
-    case 'g':
-    case 'p':
-    case 'li': {
-      // Fast track the most common tag types
-      break;
-    }
-    case 'input': {
-      // Update checked *before* name.
-      // In the middle of an update, it is possible to have multiple checked.
-      // When a checked radio tries to change name, browser makes another radio's checked false.
-      if (nextProps.type === 'radio' && nextProps.name != null) {
-        updateInputChecked(domElement, nextProps);
-      }
-      for (const propKey in lastProps) {
-        const lastProp = lastProps[propKey];
-        if (
-          lastProps.hasOwnProperty(propKey) &&
-          lastProp != null &&
-          !nextProps.hasOwnProperty(propKey)
-        ) {
-          switch (propKey) {
-            case 'checked': {
-              const checked = nextProps.defaultChecked;
-              const inputElement: HTMLInputElement = (domElement: any);
-              inputElement.checked =
-                !!checked &&
-                typeof checked !== 'function' &&
-                checked !== 'symbol';
-              break;
-            }
-            case 'value': {
-              // This is handled by updateWrapper below.
-              break;
-            }
-            // defaultChecked and defaultValue are ignored by setProp
-            default: {
-              setProp(domElement, tag, propKey, null, nextProps, lastProp);
-            }
-          }
-        }
-      }
-      for (const propKey in nextProps) {
-        const nextProp = nextProps[propKey];
-        const lastProp = lastProps[propKey];
-        if (
-          nextProps.hasOwnProperty(propKey) &&
-          nextProp !== lastProp &&
-          (nextProp != null || lastProp != null)
-        ) {
-          switch (propKey) {
-            case 'checked': {
-              const checked =
-                nextProp != null ? nextProp : nextProps.defaultChecked;
-              const inputElement: HTMLInputElement = (domElement: any);
-              inputElement.checked =
-                !!checked &&
-                typeof checked !== 'function' &&
-                checked !== 'symbol';
-              break;
-            }
-            case 'value': {
-              // This is handled by updateWrapper below.
-              break;
-            }
-            case 'children':
-            case 'dangerouslySetInnerHTML': {
-              if (nextProp != null) {
-                throw new Error(
-                  `${tag} is a void element tag and must neither have \`children\` nor ` +
-                    'use `dangerouslySetInnerHTML`.',
-                );
-              }
-              break;
-            }
-            // defaultChecked and defaultValue are ignored by setProp
-            default: {
-              setProp(domElement, tag, propKey, nextProp, nextProps, lastProp);
-            }
-          }
-        }
-      }
-
-      if (__DEV__) {
-        const wasControlled =
-          lastProps.type === 'checkbox' || lastProps.type === 'radio'
-            ? lastProps.checked != null
-            : lastProps.value != null;
-        const isControlled =
-          nextProps.type === 'checkbox' || nextProps.type === 'radio'
-            ? nextProps.checked != null
-            : nextProps.value != null;
-
-        if (
-          !wasControlled &&
-          isControlled &&
-          !didWarnUncontrolledToControlled
-        ) {
-          console.error(
-            'A component is changing an uncontrolled input to be controlled. ' +
-              'This is likely caused by the value changing from undefined to ' +
-              'a defined value, which should not happen. ' +
-              'Decide between using a controlled or uncontrolled input ' +
-              'element for the lifetime of the component. More info: https://reactjs.org/link/controlled-components',
-          );
-          didWarnUncontrolledToControlled = true;
-        }
-        if (
-          wasControlled &&
-          !isControlled &&
-          !didWarnControlledToUncontrolled
-        ) {
-          console.error(
-            'A component is changing a controlled input to be uncontrolled. ' +
-              'This is likely caused by the value changing from a defined to ' +
-              'undefined, which should not happen. ' +
-              'Decide between using a controlled or uncontrolled input ' +
-              'element for the lifetime of the component. More info: https://reactjs.org/link/controlled-components',
-          );
-          didWarnControlledToUncontrolled = true;
-        }
-      }
-      // Update the wrapper around inputs *after* updating props. This has to
-      // happen after updating the rest of props. Otherwise HTML5 input validations
-      // raise warnings and prevent the new value from being assigned.
-      updateInput(domElement, nextProps);
-      return;
-    }
-    case 'select': {
-      for (const propKey in lastProps) {
-        const lastProp = lastProps[propKey];
-        if (
-          lastProps.hasOwnProperty(propKey) &&
-          lastProp != null &&
-          !nextProps.hasOwnProperty(propKey)
-        ) {
-          switch (propKey) {
-            case 'value': {
-              // This is handled by updateWrapper below.
-              break;
-            }
-            // defaultValue are ignored by setProp
-            default: {
-              setProp(domElement, tag, propKey, null, nextProps, lastProp);
-            }
-          }
-        }
-      }
-      for (const propKey in nextProps) {
-        const nextProp = nextProps[propKey];
-        const lastProp = lastProps[propKey];
-        if (
-          nextProps.hasOwnProperty(propKey) &&
-          nextProp !== lastProp &&
-          (nextProp != null || lastProp != null)
-        ) {
-          switch (propKey) {
-            case 'value': {
-              // This is handled by updateWrapper below.
-              break;
-            }
-            // defaultValue are ignored by setProp
-            default: {
-              setProp(domElement, tag, propKey, nextProp, nextProps, lastProp);
-            }
-          }
-        }
-      }
-      // <select> value update needs to occur after <option> children
-      // reconciliation
-      updateSelect(domElement, lastProps, nextProps);
-      return;
-    }
-    case 'textarea': {
-      for (const propKey in lastProps) {
-        const lastProp = lastProps[propKey];
-        if (
-          lastProps.hasOwnProperty(propKey) &&
-          lastProp != null &&
-          !nextProps.hasOwnProperty(propKey)
-        ) {
-          switch (propKey) {
-            case 'value': {
-              // This is handled by updateWrapper below.
-              break;
-            }
-            case 'children': {
-              // TODO: This doesn't actually do anything if it updates.
-              break;
-            }
-            // defaultValue is ignored by setProp
-            default: {
-              setProp(domElement, tag, propKey, null, nextProps, lastProp);
-            }
-          }
-        }
-      }
-      for (const propKey in nextProps) {
-        const nextProp = nextProps[propKey];
-        const lastProp = lastProps[propKey];
-        if (
-          nextProps.hasOwnProperty(propKey) &&
-          nextProp !== lastProp &&
-          (nextProp != null || lastProp != null)
-        ) {
-          switch (propKey) {
-            case 'value': {
-              // This is handled by updateWrapper below.
-              break;
-            }
-            case 'children': {
-              // TODO: This doesn't actually do anything if it updates.
-              break;
-            }
-            case 'dangerouslySetInnerHTML': {
-              if (nextProp != null) {
-                // TODO: Do we really need a special error message for this. It's also pretty blunt.
-                throw new Error(
-                  '`dangerouslySetInnerHTML` does not make sense on <textarea>.',
-                );
-              }
-              break;
-            }
-            // defaultValue is ignored by setProp
-            default: {
-              setProp(domElement, tag, propKey, nextProp, nextProps, lastProp);
-            }
-          }
-        }
-      }
-      updateTextarea(domElement, nextProps);
-      return;
-    }
-    case 'option': {
-      for (const propKey in lastProps) {
-        const lastProp = lastProps[propKey];
-        if (
-          lastProps.hasOwnProperty(propKey) &&
-          lastProp != null &&
-          !nextProps.hasOwnProperty(propKey)
-        ) {
-          switch (propKey) {
-            case 'selected': {
-              // TODO: Remove support for selected on option.
-              (domElement: any).selected = false;
-              break;
-            }
-            default: {
-              setProp(domElement, tag, propKey, null, nextProps, lastProp);
-            }
-          }
-        }
-      }
-      for (const propKey in nextProps) {
-        const nextProp = nextProps[propKey];
-        const lastProp = lastProps[propKey];
-        if (
-          nextProps.hasOwnProperty(propKey) &&
-          nextProp !== lastProp &&
-          (nextProp != null || lastProp != null)
-        ) {
-          switch (propKey) {
-            case 'selected': {
-              // TODO: Remove support for selected on option.
-              (domElement: any).selected =
-                nextProp &&
-                typeof nextProp !== 'function' &&
-                typeof nextProp !== 'symbol';
-              break;
-            }
-            default: {
-              setProp(domElement, tag, propKey, nextProp, nextProps, lastProp);
-            }
-          }
-        }
-      }
-      return;
-    }
-    case 'img':
-    case 'link':
-    case 'area':
-    case 'base':
-    case 'br':
-    case 'col':
-    case 'embed':
-    case 'hr':
-    case 'keygen':
-    case 'meta':
-    case 'param':
-    case 'source':
-    case 'track':
-    case 'wbr':
-    case 'menuitem': {
-      // Void elements
-      for (const propKey in lastProps) {
-        const lastProp = lastProps[propKey];
-        if (
-          lastProps.hasOwnProperty(propKey) &&
-          lastProp != null &&
-          !nextProps.hasOwnProperty(propKey)
-        ) {
-          setProp(domElement, tag, propKey, null, nextProps, lastProp);
-        }
-      }
-      for (const propKey in nextProps) {
-        const nextProp = nextProps[propKey];
-        const lastProp = lastProps[propKey];
-        if (
-          nextProps.hasOwnProperty(propKey) &&
-          nextProp !== lastProp &&
-          (nextProp != null || lastProp != null)
-        ) {
-          switch (propKey) {
-            case 'children':
-            case 'dangerouslySetInnerHTML': {
-              if (nextProp != null) {
-                // TODO: Can we make this a DEV warning to avoid this deny list?
-                throw new Error(
-                  `${tag} is a void element tag and must neither have \`children\` nor ` +
-                    'use `dangerouslySetInnerHTML`.',
-                );
-              }
-              break;
-            }
-            // defaultChecked and defaultValue are ignored by setProp
-            default: {
-              setProp(domElement, tag, propKey, nextProp, nextProps, lastProp);
-            }
-          }
-        }
-      }
-      return;
-    }
-    default: {
-      if (isCustomElement(tag, nextProps)) {
-        for (const propKey in lastProps) {
-          const lastProp = lastProps[propKey];
-          if (
-            lastProps.hasOwnProperty(propKey) &&
-            lastProp != null &&
-            !nextProps.hasOwnProperty(propKey)
-          ) {
-            setPropOnCustomElement(
-              domElement,
-              tag,
-              propKey,
-              null,
-              nextProps,
-              lastProp,
-            );
-          }
-        }
-        for (const propKey in nextProps) {
-          const nextProp = nextProps[propKey];
-          const lastProp = lastProps[propKey];
-          if (
-            nextProps.hasOwnProperty(propKey) &&
-            nextProp !== lastProp &&
-            (nextProp != null || lastProp != null)
-          ) {
-            setPropOnCustomElement(
-              domElement,
-              tag,
-              propKey,
-              nextProp,
-              nextProps,
-              lastProp,
-            );
-          }
-        }
-        return;
-      }
-    }
-  }
-
-  for (const propKey in lastProps) {
-    const lastProp = lastProps[propKey];
-    if (
-      lastProps.hasOwnProperty(propKey) &&
-      lastProp != null &&
-      !nextProps.hasOwnProperty(propKey)
-    ) {
-      setProp(domElement, tag, propKey, null, nextProps, lastProp);
-    }
-  }
-  for (const propKey in nextProps) {
-    const nextProp = nextProps[propKey];
-    const lastProp = lastProps[propKey];
-    if (
-      nextProps.hasOwnProperty(propKey) &&
-      nextProp !== lastProp &&
-      (nextProp != null || lastProp != null)
-    ) {
-      setProp(domElement, tag, propKey, nextProp, nextProps, lastProp);
-    }
-  }
-}
-
 // Apply the diff.
-export function updatePropertiesWithDiff(
+export function updateProperties(
   domElement: Element,
   updatePayload: Array<any>,
   tag: string,
@@ -1690,7 +1252,7 @@ export function updatePropertiesWithDiff(
           }
           // defaultChecked and defaultValue are ignored by setProp
           default: {
-            setProp(domElement, tag, propKey, propValue, nextProps, null);
+            setProp(domElement, tag, propKey, propValue, nextProps);
           }
         }
       }
@@ -1751,7 +1313,7 @@ export function updatePropertiesWithDiff(
           }
           // defaultValue are ignored by setProp
           default: {
-            setProp(domElement, tag, propKey, propValue, nextProps, null);
+            setProp(domElement, tag, propKey, propValue, nextProps);
           }
         }
       }
@@ -1784,7 +1346,7 @@ export function updatePropertiesWithDiff(
           }
           // defaultValue is ignored by setProp
           default: {
-            setProp(domElement, tag, propKey, propValue, nextProps, null);
+            setProp(domElement, tag, propKey, propValue, nextProps);
           }
         }
       }
@@ -1805,7 +1367,7 @@ export function updatePropertiesWithDiff(
             break;
           }
           default: {
-            setProp(domElement, tag, propKey, propValue, nextProps, null);
+            setProp(domElement, tag, propKey, propValue, nextProps);
           }
         }
       }
@@ -1844,7 +1406,7 @@ export function updatePropertiesWithDiff(
           }
           // defaultChecked and defaultValue are ignored by setProp
           default: {
-            setProp(domElement, tag, propKey, propValue, nextProps, null);
+            setProp(domElement, tag, propKey, propValue, nextProps);
           }
         }
       }
@@ -1861,7 +1423,6 @@ export function updatePropertiesWithDiff(
             propKey,
             propValue,
             nextProps,
-            null,
           );
         }
         return;
@@ -1873,7 +1434,7 @@ export function updatePropertiesWithDiff(
   for (let i = 0; i < updatePayload.length; i += 2) {
     const propKey = updatePayload[i];
     const propValue = updatePayload[i + 1];
-    setProp(domElement, tag, propKey, propValue, nextProps, null);
+    setProp(domElement, tag, propKey, propValue, nextProps);
   }
 }
 
@@ -2816,18 +2377,7 @@ export function diffHydratedProperties(
         );
       }
       if (!isConcurrentMode || !enableClientRenderFallbackOnTextMismatch) {
-        if (diffInCommitPhase) {
-          // We really should be patching this in the commit phase but since
-          // this only affects legacy mode hydration which is deprecated anyway
-          // we can get away with it.
-          // Host singletons get their children appended and don't use the text
-          // content mechanism.
-          if (!enableHostSingletons || tag !== 'body') {
-            domElement.textContent = (children: any);
-          }
-        } else {
-          updatePayload = ['children', children];
-        }
+        updatePayload = ['children', children];
       }
     }
   }
diff --git a/packages/react-dom-bindings/src/client/ReactFiberConfigDOM.js b/packages/react-dom-bindings/src/client/ReactFiberConfigDOM.js
index 94007c299965f..8dd5252609d54 100644
--- a/packages/react-dom-bindings/src/client/ReactFiberConfigDOM.js
+++ b/packages/react-dom-bindings/src/client/ReactFiberConfigDOM.js
@@ -47,7 +47,6 @@ import {
   setInitialProperties,
   diffProperties,
   updateProperties,
-  updatePropertiesWithDiff,
   diffHydratedProperties,
   diffHydratedText,
   trapClickOnNonInteractiveElement,
@@ -87,7 +86,6 @@ import {
   enableFloat,
   enableHostSingletons,
   enableTrustedTypesIntegration,
-  diffInCommitPhase,
 } from 'shared/ReactFeatureFlags';
 import {
   HostComponent,
@@ -487,10 +485,6 @@ export function prepareUpdate(
   newProps: Props,
   hostContext: HostContext,
 ): null | Array<mixed> {
-  if (diffInCommitPhase) {
-    // TODO: Figure out how to validateDOMNesting when children turn into a string.
-    return null;
-  }
   if (__DEV__) {
     const hostContextDev = ((hostContext: any): HostContextDev);
     if (
@@ -648,26 +642,14 @@ export function commitMount(
 
 export function commitUpdate(
   domElement: Instance,
-  updatePayload: any,
+  updatePayload: Array<mixed>,
   type: string,
   oldProps: Props,
   newProps: Props,
   internalInstanceHandle: Object,
 ): void {
-  if (diffInCommitPhase) {
-    // Diff and update the properties.
-    updateProperties(domElement, type, oldProps, newProps);
-  } else {
-    // Apply the diff to the DOM node.
-    updatePropertiesWithDiff(
-      domElement,
-      updatePayload,
-      type,
-      oldProps,
-      newProps,
-    );
-  }
-
+  // Apply the diff to the DOM node.
+  updateProperties(domElement, updatePayload, type, oldProps, newProps);
   // Update the props handle so that we know which props are the ones with
   // with current event handlers.
   updateFiberProps(domElement, newProps);
diff --git a/packages/react-native-renderer/src/ReactFiberConfigFabric.js b/packages/react-native-renderer/src/ReactFiberConfigFabric.js
index 5dd36c20baafb..03ab9b6febe39 100644
--- a/packages/react-native-renderer/src/ReactFiberConfigFabric.js
+++ b/packages/react-native-renderer/src/ReactFiberConfigFabric.js
@@ -42,8 +42,6 @@ const {
   unstable_getCurrentEventPriority: fabricGetCurrentEventPriority,
 } = nativeFabricUIManager;
 
-import {diffInCommitPhase} from 'shared/ReactFeatureFlags';
-
 const {get: getViewConfigForType} = ReactNativeViewConfigRegistry;
 
 // Counter for uniquely identifying views.
@@ -290,9 +288,6 @@ export function prepareUpdate(
   newProps: Props,
   hostContext: HostContext,
 ): null | Object {
-  if (diffInCommitPhase) {
-    return null;
-  }
   const viewConfig = instance.canonical.viewConfig;
   const updatePayload = diff(oldProps, newProps, viewConfig.validAttributes);
   // TODO: If the event handlers have changed, we need to update the current props
@@ -360,27 +355,13 @@ export function cloneInstance(
   keepChildren: boolean,
   recyclableInstance: null | Instance,
 ): Instance {
-  if (diffInCommitPhase) {
-    const viewConfig = instance.canonical.viewConfig;
-    updatePayload = diff(oldProps, newProps, viewConfig.validAttributes);
-    // TODO: If the event handlers have changed, we need to update the current props
-    // in the commit phase but there is no host config hook to do it yet.
-    // So instead we hack it by updating it in the render phase.
-    instance.canonical.currentProps = newProps;
-  }
-
   const node = instance.node;
   let clone;
   if (keepChildren) {
     if (updatePayload !== null) {
       clone = cloneNodeWithNewProps(node, updatePayload);
     } else {
-      if (diffInCommitPhase) {
-        // No changes
-        return instance;
-      } else {
-        clone = cloneNode(node);
-      }
+      clone = cloneNode(node);
     }
   } else {
     if (updatePayload !== null) {
diff --git a/packages/react-noop-renderer/src/createReactNoop.js b/packages/react-noop-renderer/src/createReactNoop.js
index f32ec38806b65..fe18c12e15b6a 100644
--- a/packages/react-noop-renderer/src/createReactNoop.js
+++ b/packages/react-noop-renderer/src/createReactNoop.js
@@ -88,6 +88,7 @@ if (__DEV__) {
 
 function createReactNoop(reconciler: Function, useMutation: boolean) {
   let instanceCounter = 0;
+  let hostDiffCounter = 0;
   let hostUpdateCounter = 0;
   let hostCloneCounter = 0;
 
@@ -457,12 +458,16 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
       oldProps: Props,
       newProps: Props,
     ): null | {...} {
+      if (type === 'errorInCompletePhase') {
+        throw new Error('Error in host config.');
+      }
       if (oldProps === null) {
         throw new Error('Should have old props');
       }
       if (newProps === null) {
         throw new Error('Should have new props');
       }
+      hostDiffCounter++;
       return UPDATE_SIGNAL;
     },
 
@@ -1181,24 +1186,30 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
     },
 
     startTrackingHostCounters(): void {
+      hostDiffCounter = 0;
       hostUpdateCounter = 0;
       hostCloneCounter = 0;
     },
 
     stopTrackingHostCounters():
       | {
+          hostDiffCounter: number,
           hostUpdateCounter: number,
         }
       | {
+          hostDiffCounter: number,
           hostCloneCounter: number,
         } {
       const result = useMutation
         ? {
+            hostDiffCounter,
             hostUpdateCounter,
           }
         : {
+            hostDiffCounter,
             hostCloneCounter,
           };
+      hostDiffCounter = 0;
       hostUpdateCounter = 0;
       hostCloneCounter = 0;
 
diff --git a/packages/react-reconciler/src/ReactFiberCommitWork.js b/packages/react-reconciler/src/ReactFiberCommitWork.js
index 9ea1d95796267..3aca03988f6cd 100644
--- a/packages/react-reconciler/src/ReactFiberCommitWork.js
+++ b/packages/react-reconciler/src/ReactFiberCommitWork.js
@@ -54,7 +54,6 @@ import {
   enableFloat,
   enableLegacyHidden,
   enableHostSingletons,
-  diffInCommitPhase,
 } from 'shared/ReactFeatureFlags';
 import {
   FunctionComponent,
@@ -2775,7 +2774,7 @@ function commitMutationEffectsOnFiber(
             const updatePayload: null | UpdatePayload =
               (finishedWork.updateQueue: any);
             finishedWork.updateQueue = null;
-            if (updatePayload !== null || diffInCommitPhase) {
+            if (updatePayload !== null) {
               try {
                 commitUpdate(
                   instance,
diff --git a/packages/react-reconciler/src/ReactFiberCompleteWork.js b/packages/react-reconciler/src/ReactFiberCompleteWork.js
index c70c1256a959d..ba5f92944e029 100644
--- a/packages/react-reconciler/src/ReactFiberCompleteWork.js
+++ b/packages/react-reconciler/src/ReactFiberCompleteWork.js
@@ -38,7 +38,6 @@ import {
   enableCache,
   enableTransitionTracing,
   enableFloat,
-  diffInCommitPhase,
 } from 'shared/ReactFeatureFlags';
 
 import {resetWorkInProgressVersions as resetMutableSourceWorkInProgressVersions} from './ReactMutableSource';
@@ -433,32 +432,29 @@ function updateHostComponent(
       return;
     }
 
-    if (diffInCommitPhase) {
+    // If we get updated because one of our children updated, we don't
+    // have newProps so we'll have to reuse them.
+    // TODO: Split the update API as separate for the props vs. children.
+    // Even better would be if children weren't special cased at all tho.
+    const instance: Instance = workInProgress.stateNode;
+
+    const currentHostContext = getHostContext();
+    // TODO: Experiencing an error where oldProps is null. Suggests a host
+    // component is hitting the resume path. Figure out why. Possibly
+    // related to `hidden`.
+    const updatePayload = prepareUpdate(
+      instance,
+      type,
+      oldProps,
+      newProps,
+      currentHostContext,
+    );
+    // TODO: Type this specific to this type of component.
+    workInProgress.updateQueue = (updatePayload: any);
+    // If the update payload indicates that there is a change or if there
+    // is a new ref we mark this as an update. All the work is done in commitWork.
+    if (updatePayload) {
       markUpdate(workInProgress);
-    } else {
-      // If we get updated because one of our children updated, we don't
-      // have newProps so we'll have to reuse them.
-      // TODO: Split the update API as separate for the props vs. children.
-      // Even better would be if children weren't special cased at all tho.
-      const instance: Instance = workInProgress.stateNode;
-      // TODO: Experiencing an error where oldProps is null. Suggests a host
-      // component is hitting the resume path. Figure out why. Possibly
-      // related to `hidden`.
-      const currentHostContext = getHostContext();
-      const updatePayload = prepareUpdate(
-        instance,
-        type,
-        oldProps,
-        newProps,
-        currentHostContext,
-      );
-      // TODO: Type this specific to this type of component.
-      workInProgress.updateQueue = (updatePayload: any);
-      // If the update payload indicates that there is a change or if there
-      // is a new ref we mark this as an update. All the work is done in commitWork.
-      if (updatePayload) {
-        markUpdate(workInProgress);
-      }
     }
   } else if (supportsPersistence) {
     const currentInstance = current.stateNode;
@@ -475,22 +471,20 @@ function updateHostComponent(
     const recyclableInstance: Instance = workInProgress.stateNode;
     const currentHostContext = getHostContext();
     let updatePayload = null;
-    if (!diffInCommitPhase) {
-      if (oldProps !== newProps) {
-        updatePayload = prepareUpdate(
-          recyclableInstance,
-          type,
-          oldProps,
-          newProps,
-          currentHostContext,
-        );
-      }
-      if (childrenUnchanged && updatePayload === null) {
-        // No changes, just reuse the existing instance.
-        // Note that this might release a previous clone.
-        workInProgress.stateNode = currentInstance;
-        return;
-      }
+    if (oldProps !== newProps) {
+      updatePayload = prepareUpdate(
+        recyclableInstance,
+        type,
+        oldProps,
+        newProps,
+        currentHostContext,
+      );
+    }
+    if (childrenUnchanged && updatePayload === null) {
+      // No changes, just reuse the existing instance.
+      // Note that this might release a previous clone.
+      workInProgress.stateNode = currentInstance;
+      return;
     }
     const newInstance = cloneInstance(
       currentInstance,
@@ -502,12 +496,6 @@ function updateHostComponent(
       childrenUnchanged,
       recyclableInstance,
     );
-    if (diffInCommitPhase && newInstance === currentInstance) {
-      // No changes, just reuse the existing instance.
-      // Note that this might release a previous clone.
-      workInProgress.stateNode = currentInstance;
-      return;
-    }
 
     if (
       finalizeInitialChildren(newInstance, type, newProps, currentHostContext)
diff --git a/packages/react-reconciler/src/ReactFiberHydrationContext.js b/packages/react-reconciler/src/ReactFiberHydrationContext.js
index 7c48be5671cdc..a7b0cfdbf2b64 100644
--- a/packages/react-reconciler/src/ReactFiberHydrationContext.js
+++ b/packages/react-reconciler/src/ReactFiberHydrationContext.js
@@ -39,7 +39,6 @@ import {
   enableHostSingletons,
   enableFloat,
   enableClientRenderFallbackOnTextMismatch,
-  diffInCommitPhase,
 } from 'shared/ReactFeatureFlags';
 
 import {
@@ -688,15 +687,12 @@ function prepareToHydrateHostInstance(
     fiber,
     shouldWarnIfMismatchDev,
   );
-
   // TODO: Type this specific to this type of component.
-  if (!diffInCommitPhase) {
-    fiber.updateQueue = (updatePayload: any);
-    // If the update payload indicates that there is a change or if there
-    // is a new ref we mark this as an update.
-    if (updatePayload !== null) {
-      return true;
-    }
+  fiber.updateQueue = (updatePayload: any);
+  // If the update payload indicates that there is a change or if there
+  // is a new ref we mark this as an update.
+  if (updatePayload !== null) {
+    return true;
   }
   return false;
 }
diff --git a/packages/react-reconciler/src/__tests__/ReactIncrementalUpdatesMinimalism-test.js b/packages/react-reconciler/src/__tests__/ReactIncrementalUpdatesMinimalism-test.js
index 5f1959de160af..ddbe7eb8e7011 100644
--- a/packages/react-reconciler/src/__tests__/ReactIncrementalUpdatesMinimalism-test.js
+++ b/packages/react-reconciler/src/__tests__/ReactIncrementalUpdatesMinimalism-test.js
@@ -35,12 +35,14 @@ describe('ReactIncrementalUpdatesMinimalism', () => {
     ReactNoop.startTrackingHostCounters();
     await act(() => ReactNoop.render(<Parent />));
     expect(ReactNoop.stopTrackingHostCounters()).toEqual({
+      hostDiffCounter: 0,
       hostUpdateCounter: 0,
     });
 
     ReactNoop.startTrackingHostCounters();
     await act(() => ReactNoop.render(<Parent />));
     expect(ReactNoop.stopTrackingHostCounters()).toEqual({
+      hostDiffCounter: 1,
       hostUpdateCounter: 1,
     });
   });
@@ -73,12 +75,14 @@ describe('ReactIncrementalUpdatesMinimalism', () => {
     ReactNoop.startTrackingHostCounters();
     await act(() => ReactNoop.render(<Parent />));
     expect(ReactNoop.stopTrackingHostCounters()).toEqual({
+      hostDiffCounter: 0,
       hostUpdateCounter: 0,
     });
 
     ReactNoop.startTrackingHostCounters();
     await act(() => ReactNoop.render(<Parent />));
     expect(ReactNoop.stopTrackingHostCounters()).toEqual({
+      hostDiffCounter: 0,
       hostUpdateCounter: 0,
     });
   });
@@ -124,12 +128,17 @@ describe('ReactIncrementalUpdatesMinimalism', () => {
     ReactNoop.startTrackingHostCounters();
     await act(() => ReactNoop.render(<Parent />));
     expect(ReactNoop.stopTrackingHostCounters()).toEqual({
+      hostDiffCounter: 0,
       hostUpdateCounter: 0,
     });
 
     ReactNoop.startTrackingHostCounters();
     await act(() => childInst.setState({name: 'Robin'}));
     expect(ReactNoop.stopTrackingHostCounters()).toEqual({
+      // Child > div
+      // Child > Leaf > span
+      // Child > Leaf > span > b
+      hostDiffCounter: 3,
       // Child > div
       // Child > Leaf > span
       // Child > Leaf > span > b
@@ -150,6 +159,7 @@ describe('ReactIncrementalUpdatesMinimalism', () => {
       // Parent > section > div > hr
       // Parent > section > div > Leaf > span
       // Parent > section > div > Leaf > span > b
+      hostDiffCounter: 10,
       hostUpdateCounter: 10,
     });
   });
diff --git a/packages/react-reconciler/src/__tests__/ReactPersistentUpdatesMinimalism-test.js b/packages/react-reconciler/src/__tests__/ReactPersistentUpdatesMinimalism-test.js
index 359c80c247f02..4e17597481c5c 100644
--- a/packages/react-reconciler/src/__tests__/ReactPersistentUpdatesMinimalism-test.js
+++ b/packages/react-reconciler/src/__tests__/ReactPersistentUpdatesMinimalism-test.js
@@ -34,12 +34,14 @@ describe('ReactPersistentUpdatesMinimalism', () => {
     ReactNoopPersistent.startTrackingHostCounters();
     await act(() => ReactNoopPersistent.render(<Parent />));
     expect(ReactNoopPersistent.stopTrackingHostCounters()).toEqual({
+      hostDiffCounter: 0,
       hostCloneCounter: 0,
     });
 
     ReactNoopPersistent.startTrackingHostCounters();
     await act(() => ReactNoopPersistent.render(<Parent />));
     expect(ReactNoopPersistent.stopTrackingHostCounters()).toEqual({
+      hostDiffCounter: 1,
       hostCloneCounter: 1,
     });
   });
@@ -72,12 +74,14 @@ describe('ReactPersistentUpdatesMinimalism', () => {
     ReactNoopPersistent.startTrackingHostCounters();
     await act(() => ReactNoopPersistent.render(<Parent />));
     expect(ReactNoopPersistent.stopTrackingHostCounters()).toEqual({
+      hostDiffCounter: 0,
       hostCloneCounter: 0,
     });
 
     ReactNoopPersistent.startTrackingHostCounters();
     await act(() => ReactNoopPersistent.render(<Parent />));
     expect(ReactNoopPersistent.stopTrackingHostCounters()).toEqual({
+      hostDiffCounter: 0,
       hostCloneCounter: 0,
     });
   });
@@ -123,12 +127,17 @@ describe('ReactPersistentUpdatesMinimalism', () => {
     ReactNoopPersistent.startTrackingHostCounters();
     await act(() => ReactNoopPersistent.render(<Parent />));
     expect(ReactNoopPersistent.stopTrackingHostCounters()).toEqual({
+      hostDiffCounter: 0,
       hostCloneCounter: 0,
     });
 
     ReactNoopPersistent.startTrackingHostCounters();
     await act(() => childInst.setState({name: 'Robin'}));
     expect(ReactNoopPersistent.stopTrackingHostCounters()).toEqual({
+      // section > div > Child > div
+      // section > div > Child > Leaf > span
+      // section > div > Child > Leaf > span > b
+      hostDiffCounter: 3,
       // section
       // section > div
       // section > div > Child > div
@@ -150,6 +159,7 @@ describe('ReactPersistentUpdatesMinimalism', () => {
       // Parent > section > div > hr
       // Parent > section > div > Leaf > span
       // Parent > section > div > Leaf > span > b
+      hostDiffCounter: 10,
       hostCloneCounter: 10,
     });
   });
diff --git a/packages/react-test-renderer/src/ReactFiberConfigTestHost.js b/packages/react-test-renderer/src/ReactFiberConfigTestHost.js
index 1b7e9adcee86b..2d6c087c81f9c 100644
--- a/packages/react-test-renderer/src/ReactFiberConfigTestHost.js
+++ b/packages/react-test-renderer/src/ReactFiberConfigTestHost.js
@@ -230,7 +230,7 @@ export const supportsMutation = true;
 
 export function commitUpdate(
   instance: Instance,
-  updatePayload: null | {...},
+  updatePayload: {...},
   type: string,
   oldProps: Props,
   newProps: Props,
diff --git a/packages/shared/ReactFeatureFlags.js b/packages/shared/ReactFeatureFlags.js
index b301c3b74fe76..f3250c17fa335 100644
--- a/packages/shared/ReactFeatureFlags.js
+++ b/packages/shared/ReactFeatureFlags.js
@@ -122,9 +122,6 @@ export const enableUseEffectEventHook = __EXPERIMENTAL__;
 // (handled with an MutationObserver) instead of inline-scripts
 export const enableFizzExternalRuntime = true;
 
-// Performance related test
-export const diffInCommitPhase = __EXPERIMENTAL__;
-
 // -----------------------------------------------------------------------------
 // Chopping Block
 //
diff --git a/packages/shared/forks/ReactFeatureFlags.native-fb.js b/packages/shared/forks/ReactFeatureFlags.native-fb.js
index 729f1c7b6c271..456d78a191e25 100644
--- a/packages/shared/forks/ReactFeatureFlags.native-fb.js
+++ b/packages/shared/forks/ReactFeatureFlags.native-fb.js
@@ -82,7 +82,5 @@ export const enableHostSingletons = true;
 export const useModernStrictMode = false;
 export const enableFizzExternalRuntime = false;
 
-export const diffInCommitPhase = true;
-
 // Flow magic to verify the exports of this file match the original version.
 ((((null: any): ExportsType): FeatureFlagsType): ExportsType);
diff --git a/packages/shared/forks/ReactFeatureFlags.native-oss.js b/packages/shared/forks/ReactFeatureFlags.native-oss.js
index 25b14a8bd276c..29d464cb8833c 100644
--- a/packages/shared/forks/ReactFeatureFlags.native-oss.js
+++ b/packages/shared/forks/ReactFeatureFlags.native-oss.js
@@ -72,7 +72,5 @@ export const useModernStrictMode = false;
 export const enableFizzExternalRuntime = false;
 export const enableDeferRootSchedulingToMicrotask = true;
 
-export const diffInCommitPhase = true;
-
 // Flow magic to verify the exports of this file match the original version.
 ((((null: any): ExportsType): FeatureFlagsType): ExportsType);
diff --git a/packages/shared/forks/ReactFeatureFlags.test-renderer.js b/packages/shared/forks/ReactFeatureFlags.test-renderer.js
index aa296a97d7bbc..f102289afedde 100644
--- a/packages/shared/forks/ReactFeatureFlags.test-renderer.js
+++ b/packages/shared/forks/ReactFeatureFlags.test-renderer.js
@@ -72,7 +72,5 @@ export const useModernStrictMode = false;
 export const enableFizzExternalRuntime = false;
 export const enableDeferRootSchedulingToMicrotask = true;
 
-export const diffInCommitPhase = true;
-
 // Flow magic to verify the exports of this file match the original version.
 ((((null: any): ExportsType): FeatureFlagsType): ExportsType);
diff --git a/packages/shared/forks/ReactFeatureFlags.test-renderer.native.js b/packages/shared/forks/ReactFeatureFlags.test-renderer.native.js
index 2768dd02911d1..e1d66519d50e2 100644
--- a/packages/shared/forks/ReactFeatureFlags.test-renderer.native.js
+++ b/packages/shared/forks/ReactFeatureFlags.test-renderer.native.js
@@ -69,7 +69,5 @@ export const enableHostSingletons = true;
 export const useModernStrictMode = false;
 export const enableDeferRootSchedulingToMicrotask = true;
 
-export const diffInCommitPhase = true;
-
 // Flow magic to verify the exports of this file match the original version.
 ((((null: any): ExportsType): FeatureFlagsType): ExportsType);
diff --git a/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js b/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js
index 42bdea1bb58d8..8e7343adb750d 100644
--- a/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js
+++ b/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js
@@ -74,7 +74,5 @@ export const useModernStrictMode = false;
 export const enableFizzExternalRuntime = false;
 export const enableDeferRootSchedulingToMicrotask = true;
 
-export const diffInCommitPhase = true;
-
 // Flow magic to verify the exports of this file match the original version.
 ((((null: any): ExportsType): FeatureFlagsType): ExportsType);
diff --git a/packages/shared/forks/ReactFeatureFlags.www-dynamic.js b/packages/shared/forks/ReactFeatureFlags.www-dynamic.js
index a958bf5f66092..0926f66fc3a80 100644
--- a/packages/shared/forks/ReactFeatureFlags.www-dynamic.js
+++ b/packages/shared/forks/ReactFeatureFlags.www-dynamic.js
@@ -25,7 +25,6 @@ export const enableUnifiedSyncLane = __VARIANT__;
 export const enableTransitionTracing = __VARIANT__;
 export const enableCustomElementPropertySupport = __VARIANT__;
 export const enableDeferRootSchedulingToMicrotask = __VARIANT__;
-export const diffInCommitPhase = __VARIANT__;
 
 // Enable this flag to help with concurrent mode debugging.
 // It logs information to the console about React scheduling, rendering, and commit phases.
diff --git a/packages/shared/forks/ReactFeatureFlags.www.js b/packages/shared/forks/ReactFeatureFlags.www.js
index 98311679f2474..f0157f00f777d 100644
--- a/packages/shared/forks/ReactFeatureFlags.www.js
+++ b/packages/shared/forks/ReactFeatureFlags.www.js
@@ -29,7 +29,6 @@ export const {
   enableTransitionTracing,
   enableCustomElementPropertySupport,
   enableDeferRootSchedulingToMicrotask,
-  diffInCommitPhase,
 } = dynamicFeatureFlags;
 
 // On WWW, __EXPERIMENTAL__ is used for a new modern build.