diff --git a/packages/react-reconciler/src/SchedulingProfiler.js b/packages/react-reconciler/src/SchedulingProfiler.js
index 4c2a18b780e6..1c69edebcbb7 100644
--- a/packages/react-reconciler/src/SchedulingProfiler.js
+++ b/packages/react-reconciler/src/SchedulingProfiler.js
@@ -20,31 +20,63 @@ import getComponentName from 'shared/getComponentName';
  * require.
  */
 const supportsUserTiming =
-  typeof performance !== 'undefined' && typeof performance.mark === 'function';
+  typeof performance !== 'undefined' &&
+  typeof performance.mark === 'function' &&
+  typeof performance.clearMarks === 'function';
+
+let supportsUserTimingV3 = false;
+if (enableSchedulingProfiler) {
+  if (supportsUserTiming) {
+    const CHECK_V3_MARK = '__v3';
+    const markOptions = {};
+    // $FlowFixMe: Ignore Flow complaining about needing a value
+    Object.defineProperty(markOptions, 'startTime', {
+      get: function() {
+        supportsUserTimingV3 = true;
+        return 0;
+      },
+      set: function() {},
+    });
+
+    try {
+      // $FlowFixMe: Flow expects the User Timing level 2 API.
+      performance.mark(CHECK_V3_MARK, markOptions);
+    } catch (error) {
+      // Ignore
+    } finally {
+      performance.clearMarks(CHECK_V3_MARK);
+    }
+  }
+}
 
 function formatLanes(laneOrLanes: Lane | Lanes): string {
   return ((laneOrLanes: any): number).toString();
 }
 
+function markAndClear(name) {
+  performance.mark(name);
+  performance.clearMarks(name);
+}
+
 // Create a mark on React initialization
 if (enableSchedulingProfiler) {
-  if (supportsUserTiming) {
-    performance.mark(`--react-init-${ReactVersion}`);
+  if (supportsUserTimingV3) {
+    markAndClear(`--react-init-${ReactVersion}`);
   }
 }
 
 export function markCommitStarted(lanes: Lanes): void {
   if (enableSchedulingProfiler) {
-    if (supportsUserTiming) {
-      performance.mark(`--commit-start-${formatLanes(lanes)}`);
+    if (supportsUserTimingV3) {
+      markAndClear(`--commit-start-${formatLanes(lanes)}`);
     }
   }
 }
 
 export function markCommitStopped(): void {
   if (enableSchedulingProfiler) {
-    if (supportsUserTiming) {
-      performance.mark('--commit-stop');
+    if (supportsUserTimingV3) {
+      markAndClear('--commit-stop');
     }
   }
 }
@@ -63,14 +95,14 @@ function getWakeableID(wakeable: Wakeable): number {
 
 export function markComponentSuspended(fiber: Fiber, wakeable: Wakeable): void {
   if (enableSchedulingProfiler) {
-    if (supportsUserTiming) {
+    if (supportsUserTimingV3) {
       const id = getWakeableID(wakeable);
       const componentName = getComponentName(fiber.type) || 'Unknown';
       // TODO Add component stack id
-      performance.mark(`--suspense-suspend-${id}-${componentName}`);
+      markAndClear(`--suspense-suspend-${id}-${componentName}`);
       wakeable.then(
-        () => performance.mark(`--suspense-resolved-${id}-${componentName}`),
-        () => performance.mark(`--suspense-rejected-${id}-${componentName}`),
+        () => markAndClear(`--suspense-resolved-${id}-${componentName}`),
+        () => markAndClear(`--suspense-rejected-${id}-${componentName}`),
       );
     }
   }
@@ -78,74 +110,74 @@ export function markComponentSuspended(fiber: Fiber, wakeable: Wakeable): void {
 
 export function markLayoutEffectsStarted(lanes: Lanes): void {
   if (enableSchedulingProfiler) {
-    if (supportsUserTiming) {
-      performance.mark(`--layout-effects-start-${formatLanes(lanes)}`);
+    if (supportsUserTimingV3) {
+      markAndClear(`--layout-effects-start-${formatLanes(lanes)}`);
     }
   }
 }
 
 export function markLayoutEffectsStopped(): void {
   if (enableSchedulingProfiler) {
-    if (supportsUserTiming) {
-      performance.mark('--layout-effects-stop');
+    if (supportsUserTimingV3) {
+      markAndClear('--layout-effects-stop');
     }
   }
 }
 
 export function markPassiveEffectsStarted(lanes: Lanes): void {
   if (enableSchedulingProfiler) {
-    if (supportsUserTiming) {
-      performance.mark(`--passive-effects-start-${formatLanes(lanes)}`);
+    if (supportsUserTimingV3) {
+      markAndClear(`--passive-effects-start-${formatLanes(lanes)}`);
     }
   }
 }
 
 export function markPassiveEffectsStopped(): void {
   if (enableSchedulingProfiler) {
-    if (supportsUserTiming) {
-      performance.mark('--passive-effects-stop');
+    if (supportsUserTimingV3) {
+      markAndClear('--passive-effects-stop');
     }
   }
 }
 
 export function markRenderStarted(lanes: Lanes): void {
   if (enableSchedulingProfiler) {
-    if (supportsUserTiming) {
-      performance.mark(`--render-start-${formatLanes(lanes)}`);
+    if (supportsUserTimingV3) {
+      markAndClear(`--render-start-${formatLanes(lanes)}`);
     }
   }
 }
 
 export function markRenderYielded(): void {
   if (enableSchedulingProfiler) {
-    if (supportsUserTiming) {
-      performance.mark('--render-yield');
+    if (supportsUserTimingV3) {
+      markAndClear('--render-yield');
     }
   }
 }
 
 export function markRenderStopped(): void {
   if (enableSchedulingProfiler) {
-    if (supportsUserTiming) {
-      performance.mark('--render-stop');
+    if (supportsUserTimingV3) {
+      markAndClear('--render-stop');
     }
   }
 }
 
 export function markRenderScheduled(lane: Lane): void {
   if (enableSchedulingProfiler) {
-    if (supportsUserTiming) {
-      performance.mark(`--schedule-render-${formatLanes(lane)}`);
+    if (supportsUserTimingV3) {
+      markAndClear(`--schedule-render-${formatLanes(lane)}`);
     }
   }
 }
 
 export function markForceUpdateScheduled(fiber: Fiber, lane: Lane): void {
   if (enableSchedulingProfiler) {
-    if (supportsUserTiming) {
+    if (supportsUserTimingV3) {
       const componentName = getComponentName(fiber.type) || 'Unknown';
       // TODO Add component stack id
-      performance.mark(
+      markAndClear(
         `--schedule-forced-update-${formatLanes(lane)}-${componentName}`,
       );
     }
@@ -154,10 +186,10 @@ export function markForceUpdateScheduled(fiber: Fiber, lane: Lane): void {
 
 export function markStateUpdateScheduled(fiber: Fiber, lane: Lane): void {
   if (enableSchedulingProfiler) {
-    if (supportsUserTiming) {
+    if (supportsUserTimingV3) {
       const componentName = getComponentName(fiber.type) || 'Unknown';
       // TODO Add component stack id
-      performance.mark(
+      markAndClear(
         `--schedule-state-update-${formatLanes(lane)}-${componentName}`,
       );
     }
diff --git a/packages/react-reconciler/src/__tests__/SchedulingProfiler-test.internal.js b/packages/react-reconciler/src/__tests__/SchedulingProfiler-test.internal.js
index 55f8d3617c0d..35c854e4b2e7 100644
--- a/packages/react-reconciler/src/__tests__/SchedulingProfiler-test.internal.js
+++ b/packages/react-reconciler/src/__tests__/SchedulingProfiler-test.internal.js
@@ -18,22 +18,56 @@ describe('SchedulingProfiler', () => {
   let ReactNoop;
   let Scheduler;
 
+  let clearedMarks;
+  let featureDetectionMarkName = null;
   let marks;
 
   function createUserTimingPolyfill() {
+    featureDetectionMarkName = null;
+
+    clearedMarks = [];
+    marks = [];
+
     // This is not a true polyfill, but it gives us enough to capture marks.
     // Reference: https://developer.mozilla.org/en-US/docs/Web/API/User_Timing_API
     return {
-      mark(markName) {
+      clearMarks(markName) {
+        clearedMarks.push(markName);
+        marks = marks.filter(mark => mark !== markName);
+      },
+      mark(markName, markOptions) {
+        if (featureDetectionMarkName === null) {
+          featureDetectionMarkName = markName;
+        }
         marks.push(markName);
+        if (markOptions != null) {
+          // This is triggers the feature detection.
+          markOptions.startTime++;
+        }
       },
     };
   }
 
+  function clearPendingMarks() {
+    clearedMarks.splice(0);
+  }
+
+  function expectMarksToContain(expectedMarks) {
+    expect(clearedMarks).toContain(expectedMarks);
+  }
+
+  function expectMarksToEqual(expectedMarks) {
+    expect(
+      clearedMarks[0] === featureDetectionMarkName
+        ? clearedMarks.slice(1)
+        : clearedMarks,
+    ).toEqual(expectedMarks);
+  }
+
   beforeEach(() => {
     jest.resetModules();
+
     global.performance = createUserTimingPolyfill();
-    marks = [];
 
     React = require('react');
 
@@ -45,25 +79,28 @@ describe('SchedulingProfiler', () => {
   });
 
   afterEach(() => {
+    // Verify all logged marks also get cleared.
+    expect(marks).toHaveLength(0);
+
     delete global.performance;
   });
 
   // @gate !enableSchedulingProfiler
   it('should not mark if enableSchedulingProfiler is false', () => {
     ReactTestRenderer.create(<div />);
-    expect(marks).toEqual([]);
+    expectMarksToEqual([]);
   });
 
   // @gate enableSchedulingProfiler
   it('should log React version on initialization', () => {
-    expect(marks).toEqual([`--react-init-${ReactVersion}`]);
+    expectMarksToEqual([`--react-init-${ReactVersion}`]);
   });
 
   // @gate enableSchedulingProfiler
   it('should mark sync render without suspends or state updates', () => {
     ReactTestRenderer.create(<div />);
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       `--react-init-${ReactVersion}`,
       '--schedule-render-1',
       '--render-start-1',
@@ -79,16 +116,16 @@ describe('SchedulingProfiler', () => {
   it('should mark concurrent render without suspends or state updates', () => {
     ReactTestRenderer.create(<div />, {unstable_isConcurrent: true});
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       `--react-init-${ReactVersion}`,
       '--schedule-render-512',
     ]);
 
-    marks.splice(0);
+    clearPendingMarks();
 
     expect(Scheduler).toFlushUntilNextPaint([]);
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       '--render-start-512',
       '--render-stop',
       '--commit-start-512',
@@ -114,7 +151,7 @@ describe('SchedulingProfiler', () => {
     // Do one step of work.
     expect(ReactNoop.flushNextYield()).toEqual(['Foo']);
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       `--react-init-${ReactVersion}`,
       '--schedule-render-512',
       '--render-start-512',
@@ -135,7 +172,7 @@ describe('SchedulingProfiler', () => {
       </React.Suspense>,
     );
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       `--react-init-${ReactVersion}`,
       '--schedule-render-1',
       '--render-start-1',
@@ -147,10 +184,10 @@ describe('SchedulingProfiler', () => {
       '--commit-stop',
     ]);
 
-    marks.splice(0);
+    clearPendingMarks();
 
     await fakeSuspensePromise;
-    expect(marks).toEqual(['--suspense-resolved-0-Example']);
+    expectMarksToEqual(['--suspense-resolved-0-Example']);
   });
 
   // @gate enableSchedulingProfiler
@@ -166,7 +203,7 @@ describe('SchedulingProfiler', () => {
       </React.Suspense>,
     );
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       `--react-init-${ReactVersion}`,
       '--schedule-render-1',
       '--render-start-1',
@@ -178,10 +215,10 @@ describe('SchedulingProfiler', () => {
       '--commit-stop',
     ]);
 
-    marks.splice(0);
+    clearPendingMarks();
 
     await expect(fakeSuspensePromise).rejects.toThrow();
-    expect(marks).toEqual(['--suspense-rejected-0-Example']);
+    expectMarksToEqual(['--suspense-rejected-0-Example']);
   });
 
   // @gate enableSchedulingProfiler
@@ -198,16 +235,16 @@ describe('SchedulingProfiler', () => {
       {unstable_isConcurrent: true},
     );
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       `--react-init-${ReactVersion}`,
       '--schedule-render-512',
     ]);
 
-    marks.splice(0);
+    clearPendingMarks();
 
     expect(Scheduler).toFlushUntilNextPaint([]);
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       '--render-start-512',
       '--suspense-suspend-0-Example',
       '--render-stop',
@@ -217,10 +254,10 @@ describe('SchedulingProfiler', () => {
       '--commit-stop',
     ]);
 
-    marks.splice(0);
+    clearPendingMarks();
 
     await fakeSuspensePromise;
-    expect(marks).toEqual(['--suspense-resolved-0-Example']);
+    expectMarksToEqual(['--suspense-resolved-0-Example']);
   });
 
   // @gate enableSchedulingProfiler
@@ -237,16 +274,16 @@ describe('SchedulingProfiler', () => {
       {unstable_isConcurrent: true},
     );
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       `--react-init-${ReactVersion}`,
       '--schedule-render-512',
     ]);
 
-    marks.splice(0);
+    clearPendingMarks();
 
     expect(Scheduler).toFlushUntilNextPaint([]);
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       '--render-start-512',
       '--suspense-suspend-0-Example',
       '--render-stop',
@@ -256,10 +293,10 @@ describe('SchedulingProfiler', () => {
       '--commit-stop',
     ]);
 
-    marks.splice(0);
+    clearPendingMarks();
 
     await expect(fakeSuspensePromise).rejects.toThrow();
-    expect(marks).toEqual(['--suspense-rejected-0-Example']);
+    expectMarksToEqual(['--suspense-rejected-0-Example']);
   });
 
   // @gate enableSchedulingProfiler
@@ -276,16 +313,16 @@ describe('SchedulingProfiler', () => {
 
     ReactTestRenderer.create(<Example />, {unstable_isConcurrent: true});
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       `--react-init-${ReactVersion}`,
       '--schedule-render-512',
     ]);
 
-    marks.splice(0);
+    clearPendingMarks();
 
     expect(Scheduler).toFlushUntilNextPaint([]);
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       '--render-start-512',
       '--render-stop',
       '--commit-start-512',
@@ -313,16 +350,16 @@ describe('SchedulingProfiler', () => {
 
     ReactTestRenderer.create(<Example />, {unstable_isConcurrent: true});
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       `--react-init-${ReactVersion}`,
       '--schedule-render-512',
     ]);
 
-    marks.splice(0);
+    clearPendingMarks();
 
     expect(Scheduler).toFlushUntilNextPaint([]);
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       '--render-start-512',
       '--render-stop',
       '--commit-start-512',
@@ -351,12 +388,12 @@ describe('SchedulingProfiler', () => {
 
     ReactTestRenderer.create(<Example />, {unstable_isConcurrent: true});
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       `--react-init-${ReactVersion}`,
       '--schedule-render-512',
     ]);
 
-    marks.splice(0);
+    clearPendingMarks();
 
     expect(() => {
       expect(Scheduler).toFlushUntilNextPaint([]);
@@ -364,8 +401,8 @@ describe('SchedulingProfiler', () => {
 
     gate(({old}) =>
       old
-        ? expect(marks).toContain('--schedule-state-update-1024-Example')
-        : expect(marks).toContain('--schedule-state-update-512-Example'),
+        ? expectMarksToContain('--schedule-state-update-1024-Example')
+        : expectMarksToContain('--schedule-state-update-512-Example'),
     );
   });
 
@@ -383,12 +420,12 @@ describe('SchedulingProfiler', () => {
 
     ReactTestRenderer.create(<Example />, {unstable_isConcurrent: true});
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       `--react-init-${ReactVersion}`,
       '--schedule-render-512',
     ]);
 
-    marks.splice(0);
+    clearPendingMarks();
 
     expect(() => {
       expect(Scheduler).toFlushUntilNextPaint([]);
@@ -396,8 +433,8 @@ describe('SchedulingProfiler', () => {
 
     gate(({old}) =>
       old
-        ? expect(marks).toContain('--schedule-forced-update-1024-Example')
-        : expect(marks).toContain('--schedule-forced-update-512-Example'),
+        ? expectMarksToContain('--schedule-forced-update-1024-Example')
+        : expectMarksToContain('--schedule-forced-update-512-Example'),
     );
   });
 
@@ -413,16 +450,16 @@ describe('SchedulingProfiler', () => {
 
     ReactTestRenderer.create(<Example />, {unstable_isConcurrent: true});
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       `--react-init-${ReactVersion}`,
       '--schedule-render-512',
     ]);
 
-    marks.splice(0);
+    clearPendingMarks();
 
     expect(Scheduler).toFlushUntilNextPaint([]);
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       '--render-start-512',
       '--render-stop',
       '--commit-start-512',
@@ -451,7 +488,7 @@ describe('SchedulingProfiler', () => {
       ReactTestRenderer.create(<Example />, {unstable_isConcurrent: true});
     });
 
-    expect(marks).toEqual([
+    expectMarksToEqual([
       `--react-init-${ReactVersion}`,
       '--schedule-render-512',
       '--render-start-512',
@@ -486,8 +523,8 @@ describe('SchedulingProfiler', () => {
 
     gate(({old}) =>
       old
-        ? expect(marks).toContain('--schedule-state-update-1024-Example')
-        : expect(marks).toContain('--schedule-state-update-512-Example'),
+        ? expectMarksToContain('--schedule-state-update-1024-Example')
+        : expectMarksToContain('--schedule-state-update-512-Example'),
     );
   });
 });
diff --git a/packages/shared/forks/ReactFeatureFlags.www-dynamic.js b/packages/shared/forks/ReactFeatureFlags.www-dynamic.js
index 95ba1859e150..1321bf70bab2 100644
--- a/packages/shared/forks/ReactFeatureFlags.www-dynamic.js
+++ b/packages/shared/forks/ReactFeatureFlags.www-dynamic.js
@@ -25,6 +25,8 @@ export const decoupleUpdatePriorityFromScheduler = __VARIANT__;
 // NOTE: This feature will only work in DEV mode; all callsights are wrapped with __DEV__.
 export const enableDebugTracing = __EXPERIMENTAL__;
 
+export const enableSchedulingProfiler = __VARIANT__;
+
 // This only has an effect in the new reconciler. But also, the new reconciler
 // is only enabled when __VARIANT__ is true. So this is set to the opposite of
 // __VARIANT__ so that it's `false` when running against the new reconciler.
diff --git a/packages/shared/forks/ReactFeatureFlags.www.js b/packages/shared/forks/ReactFeatureFlags.www.js
index 947b05ab8530..70d68cef060b 100644
--- a/packages/shared/forks/ReactFeatureFlags.www.js
+++ b/packages/shared/forks/ReactFeatureFlags.www.js
@@ -40,7 +40,8 @@ export const enableProfilerNestedUpdateScheduledHook =
   __PROFILE__ && dynamicFeatureFlags.enableProfilerNestedUpdateScheduledHook;
 
 // Logs additional User Timing API marks for use with an experimental profiling tool.
-export const enableSchedulingProfiler = __PROFILE__;
+export const enableSchedulingProfiler =
+  __PROFILE__ && dynamicFeatureFlags.enableSchedulingProfiler;
 
 // Note: we'll want to remove this when we to userland implementation.
 // For now, we'll turn it on for everyone because it's *already* on for everyone in practice.