diff --git a/src/actions/profile-view.ts b/src/actions/profile-view.ts
index 5cc91261f3..43af88bb8b 100644
--- a/src/actions/profile-view.ts
+++ b/src/actions/profile-view.ts
@@ -1749,13 +1749,17 @@ export function changeShowJsTracerSummary(
 }
 
 export function updatePreviewSelection(
-  previewSelection: PreviewSelection
+  previewSelection: PreviewSelection | null
 ): ThunkAction<void> {
   return (dispatch, getState) => {
+    // Only dispatch if the selection changes. This function can fire in a tight loop,
+    // and this check saves a dispatch.
     const currentPreviewSelection = getPreviewSelection(getState());
-    if (!objectShallowEquals(currentPreviewSelection, previewSelection)) {
-      // Only dispatch if the selection changes. This function can fire in a tight loop,
-      // and this check saves a dispatch.
+    if (
+      !currentPreviewSelection ||
+      !previewSelection ||
+      !objectShallowEquals(currentPreviewSelection, previewSelection)
+    ) {
       dispatch({
         type: 'UPDATE_PREVIEW_SELECTION',
         previewSelection,
diff --git a/src/components/app/BottomBox.tsx b/src/components/app/BottomBox.tsx
index 8ab0b1448c..299320261c 100644
--- a/src/components/app/BottomBox.tsx
+++ b/src/components/app/BottomBox.tsx
@@ -28,7 +28,7 @@ import {
   getSourceViewCode,
   getAssemblyViewCode,
 } from 'firefox-profiler/selectors/code';
-import { getPreviewSelection } from 'firefox-profiler/selectors/profile';
+import { getPreviewSelectionIsBeingModified } from 'firefox-profiler/selectors/profile';
 import explicitConnect from 'firefox-profiler/utils/connect';
 
 import type { ConnectedProps } from 'firefox-profiler/utils/connect';
@@ -295,7 +295,7 @@ export const BottomBox = explicitConnect<{}, StateProps, DispatchProps>({
       selectedNodeSelectors.getAssemblyViewAddressTimings(state),
     assemblyViewScrollGeneration: getAssemblyViewScrollGeneration(state),
     assemblyViewIsOpen: getAssemblyViewIsOpen(state),
-    disableOverscan: getPreviewSelection(state).isModifying,
+    disableOverscan: getPreviewSelectionIsBeingModified(state),
   }),
   mapDispatchToProps: {
     closeBottomBox,
diff --git a/src/components/app/ProfileFilterNavigator.tsx b/src/components/app/ProfileFilterNavigator.tsx
index 6d43a1ddc5..d4bb3873a8 100644
--- a/src/components/app/ProfileFilterNavigator.tsx
+++ b/src/components/app/ProfileFilterNavigator.tsx
@@ -187,7 +187,7 @@ export const ProfileFilterNavigator = explicitConnect<
     const items = getCommittedRangeLabels(state);
     const previewSelection = getPreviewSelection(state);
     const profileTimelineUnit = getProfileTimelineUnit(state);
-    const uncommittedItem = previewSelection.hasSelection
+    const uncommittedItem = previewSelection
       ? getFormattedTimelineValue(
           previewSelection.selectionEnd - previewSelection.selectionStart,
           profileTimelineUnit
diff --git a/src/components/calltree/CallTree.tsx b/src/components/calltree/CallTree.tsx
index 082c83c570..02e6b7333d 100644
--- a/src/components/calltree/CallTree.tsx
+++ b/src/components/calltree/CallTree.tsx
@@ -16,7 +16,7 @@ import {
 import {
   getScrollToSelectionGeneration,
   getFocusCallTreeGeneration,
-  getPreviewSelection,
+  getPreviewSelectionIsBeingModified,
   getCategories,
   getCurrentTableViewOptions,
 } from 'firefox-profiler/selectors/profile';
@@ -410,7 +410,7 @@ export const CallTree = explicitConnect<{}, StateProps, DispatchProps>({
     expandedCallNodeIndexes:
       selectedThreadSelectors.getExpandedCallNodeIndexes(state),
     searchStringsRegExp: getSearchStringsAsRegExp(state),
-    disableOverscan: getPreviewSelection(state).isModifying,
+    disableOverscan: getPreviewSelectionIsBeingModified(state),
     invertCallstack: getInvertCallstack(state),
     implementationFilter: getImplementationFilter(state),
     // Use the filtered call node max depth, rather than the preview filtered call node
diff --git a/src/components/flame-graph/FlameGraph.tsx b/src/components/flame-graph/FlameGraph.tsx
index 3b733e11e6..7eaf02af41 100644
--- a/src/components/flame-graph/FlameGraph.tsx
+++ b/src/components/flame-graph/FlameGraph.tsx
@@ -74,7 +74,7 @@ type StateProps = {
   readonly ctssSampleIndexOffset: number;
   readonly maxStackDepthPlusOne: number;
   readonly timeRange: StartEndRange;
-  readonly previewSelection: PreviewSelection;
+  readonly previewSelection: PreviewSelection | null;
   readonly flameGraphTiming: FlameGraphTiming;
   readonly callTree: CallTree;
   readonly callNodeInfo: CallNodeInfo;
diff --git a/src/components/js-tracer/Canvas.tsx b/src/components/js-tracer/Canvas.tsx
index c748609d75..abed86ac95 100644
--- a/src/components/js-tracer/Canvas.tsx
+++ b/src/components/js-tracer/Canvas.tsx
@@ -608,7 +608,6 @@ class JsTracerCanvasImpl extends React.PureComponent<Props, State> {
     // const { markers, updatePreviewSelection } = this.props;
     // const marker = markers[eventIndex];
     // updatePreviewSelection({
-    //   hasSelection: true,
     //   isModifying: false,
     //   selectionStart: marker.start,
     //   selectionEnd: marker.start + marker.dur,
diff --git a/src/components/js-tracer/Chart.tsx b/src/components/js-tracer/Chart.tsx
index afea714125..c980c96d93 100644
--- a/src/components/js-tracer/Chart.tsx
+++ b/src/components/js-tracer/Chart.tsx
@@ -53,7 +53,7 @@ type StateProps = {
   readonly stringTable: StringTable;
   readonly timeRange: StartEndRange;
   readonly threadsKey: ThreadsKey;
-  readonly previewSelection: PreviewSelection;
+  readonly previewSelection: PreviewSelection | null;
 };
 
 type Props = ConnectedProps<OwnProps, StateProps, DispatchProps>;
diff --git a/src/components/marker-chart/Canvas.tsx b/src/components/marker-chart/Canvas.tsx
index b8d72b5349..5964f4599c 100644
--- a/src/components/marker-chart/Canvas.tsx
+++ b/src/components/marker-chart/Canvas.tsx
@@ -775,7 +775,6 @@ class MarkerChartCanvasImpl extends React.PureComponent<Props> {
     );
 
     updatePreviewSelection({
-      hasSelection: true,
       isModifying: false,
       selectionStart: start,
       selectionEnd: end,
diff --git a/src/components/marker-chart/index.tsx b/src/components/marker-chart/index.tsx
index 4e487ddeeb..ec93715ef0 100644
--- a/src/components/marker-chart/index.tsx
+++ b/src/components/marker-chart/index.tsx
@@ -56,7 +56,7 @@ type StateProps = {
   readonly markerListLength: number;
   readonly timeRange: StartEndRange;
   readonly threadsKey: ThreadsKey;
-  readonly previewSelection: PreviewSelection;
+  readonly previewSelection: PreviewSelection | null;
   readonly rightClickedMarkerIndex: MarkerIndex | null;
   readonly selectedMarkerIndex: MarkerIndex | null;
 };
diff --git a/src/components/network-chart/index.tsx b/src/components/network-chart/index.tsx
index 3d61cd247d..07ba63baec 100644
--- a/src/components/network-chart/index.tsx
+++ b/src/components/network-chart/index.tsx
@@ -19,7 +19,7 @@ import {
 
 import {
   getScrollToSelectionGeneration,
-  getPreviewSelection,
+  getPreviewSelectionIsBeingModified,
   getPreviewSelectionRange,
 } from '../../selectors/profile';
 import { selectedThreadSelectors } from '../../selectors/per-thread';
@@ -422,7 +422,7 @@ export const NetworkChart = explicitConnect<
     hoveredMarkerIndexFromState:
       selectedThreadSelectors.getHoveredMarkerIndex(state),
     timeRange: getPreviewSelectionRange(state),
-    disableOverscan: getPreviewSelection(state).isModifying,
+    disableOverscan: getPreviewSelectionIsBeingModified(state),
     threadsKey: getSelectedThreadsKey(state),
   }),
   mapDispatchToProps: {
diff --git a/src/components/shared/Draggable.tsx b/src/components/shared/Draggable.tsx
index a1094eace1..c463d035e6 100644
--- a/src/components/shared/Draggable.tsx
+++ b/src/components/shared/Draggable.tsx
@@ -3,24 +3,17 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 import * as React from 'react';
-import type { Milliseconds } from 'firefox-profiler/types';
 
-export type OnMove = (
-  originalValue: {
-    readonly selectionEnd: Milliseconds;
-    readonly selectionStart: Milliseconds;
-  },
+export type OnMove<T> = (
+  originalValue: T,
   dx: number,
   dy: number,
   isModifying: boolean
 ) => void;
 
-type Props = {
-  value: {
-    readonly selectionStart: Milliseconds;
-    readonly selectionEnd: Milliseconds;
-  };
-  onMove: OnMove;
+type Props<T> = {
+  value: T;
+  onMove: OnMove<T>;
   className: string;
   children?: React.ReactNode;
 };
@@ -37,7 +30,7 @@ type State = {
  * x and y deltas compared to the mouse position at mousedown.
  * During the drag, the additional className 'dragging' is set on the element.
  */
-export class Draggable extends React.PureComponent<Props, State> {
+export class Draggable<T> extends React.PureComponent<Props<T>, State> {
   _container: HTMLDivElement | null = null;
   _handlers: {
     mouseMoveHandler: (param: MouseEvent) => void;
diff --git a/src/components/shared/MarkerContextMenu.tsx b/src/components/shared/MarkerContextMenu.tsx
index a513c646c8..bd4a4a8fe2 100644
--- a/src/components/shared/MarkerContextMenu.tsx
+++ b/src/components/shared/MarkerContextMenu.tsx
@@ -52,7 +52,7 @@ type OwnProps = {
 type StateProps = {
   readonly marker: Marker;
   readonly markerIndex: MarkerIndex;
-  readonly previewSelection: PreviewSelection;
+  readonly previewSelection: PreviewSelection | null;
   readonly committedRange: StartEndRange;
   readonly thread: Thread | null;
   readonly implementationFilter: ImplementationFilter;
@@ -74,12 +74,11 @@ class MarkerContextMenuImpl extends PureComponent<Props> {
     const { updatePreviewSelection, previewSelection, committedRange } =
       this.props;
 
-    const selectionEnd = previewSelection.hasSelection
+    const selectionEnd = previewSelection
       ? previewSelection.selectionEnd
       : committedRange.end;
 
     updatePreviewSelection({
-      hasSelection: true,
       isModifying: false,
       selectionStart,
       selectionEnd,
@@ -90,7 +89,7 @@ class MarkerContextMenuImpl extends PureComponent<Props> {
     const { updatePreviewSelection, committedRange, previewSelection } =
       this.props;
 
-    const selectionStart = previewSelection.hasSelection
+    const selectionStart = previewSelection
       ? previewSelection.selectionStart
       : committedRange.start;
 
@@ -102,7 +101,6 @@ class MarkerContextMenuImpl extends PureComponent<Props> {
     }
 
     updatePreviewSelection({
-      hasSelection: true,
       isModifying: false,
       selectionStart,
       selectionEnd,
@@ -137,7 +135,6 @@ class MarkerContextMenuImpl extends PureComponent<Props> {
     }
 
     updatePreviewSelection({
-      hasSelection: true,
       isModifying: false,
       selectionStart: marker.start,
       selectionEnd: marker.end,
@@ -385,11 +382,11 @@ class MarkerContextMenuImpl extends PureComponent<Props> {
     const { marker, previewSelection, committedRange } = this.props;
     const { data } = marker;
 
-    const selectionEnd = previewSelection.hasSelection
+    const selectionEnd = previewSelection
       ? previewSelection.selectionEnd
       : committedRange.end;
 
-    const selectionStart = previewSelection.hasSelection
+    const selectionStart = previewSelection
       ? previewSelection.selectionStart
       : committedRange.start;
 
diff --git a/src/components/shared/chart/Viewport.tsx b/src/components/shared/chart/Viewport.tsx
index 6f9c989290..4471702639 100644
--- a/src/components/shared/chart/Viewport.tsx
+++ b/src/components/shared/chart/Viewport.tsx
@@ -145,7 +145,7 @@ type ViewportProps<ChartProps> = {
   // The "committed range", whose endpoints correspond to 0 and 1.
   readonly timeRange: StartEndRange;
   // The preview selection, whose endpoints correspond to viewportLeft and viewportRight.
-  readonly previewSelection: PreviewSelection;
+  readonly previewSelection: PreviewSelection | null;
   // The left margin. Margins are outside the viewport but inside containerWidth.
   readonly marginLeft: CssPixels;
   // The right margin. Margins are outside the viewport but inside containerWidth.
@@ -214,7 +214,7 @@ class ChartViewportImpl<OwnProps> extends React.PureComponent<
 > {
   zoomScrollId: number = 0;
   _pendingPreviewSelectionUpdates: Array<
-    (horizontalViewport: HorizontalViewport) => PreviewSelection
+    (horizontalViewport: HorizontalViewport) => PreviewSelection | null
   > = [];
   _container: HTMLDivElement | null = null;
   _takeContainerRef = (container: HTMLDivElement) => {
@@ -235,10 +235,10 @@ class ChartViewportImpl<OwnProps> extends React.PureComponent<
   }
 
   getHorizontalViewport(
-    previewSelection: PreviewSelection,
+    previewSelection: PreviewSelection | null,
     timeRange: StartEndRange
   ) {
-    if (previewSelection.hasSelection) {
+    if (previewSelection) {
       const { selectionStart, selectionEnd } = previewSelection;
       const timeRangeLength = timeRange.end - timeRange.start;
       return {
@@ -433,7 +433,7 @@ class ChartViewportImpl<OwnProps> extends React.PureComponent<
    * processes all queued updates from a requestAnimationFrame callback.
    */
   _addBatchedPreviewSelectionUpdate(
-    callback: (param: HorizontalViewport) => PreviewSelection
+    callback: (param: HorizontalViewport) => PreviewSelection | null
   ) {
     if (this._pendingPreviewSelectionUpdates.length === 0) {
       requestAnimationFrame(() => this._flushPendingPreviewSelectionUpdates());
@@ -532,14 +532,10 @@ class ChartViewportImpl<OwnProps> extends React.PureComponent<
           viewportProps: { timeRange },
         } = this.props;
         if (newViewportLeft === 0 && newViewportRight === 1) {
-          return {
-            hasSelection: false,
-            isModifying: false,
-          };
+          return null;
         }
         const timeRangeLength = timeRange.end - timeRange.start;
         return {
-          hasSelection: true,
           isModifying: false,
           selectionStart: timeRange.start + timeRangeLength * newViewportLeft,
           selectionEnd: timeRange.start + timeRangeLength * newViewportRight,
@@ -722,10 +718,7 @@ class ChartViewportImpl<OwnProps> extends React.PureComponent<
           // Calculate left and right in terms of the unit interval of the profile range.
           const viewportLength = viewportRight - viewportLeft;
           if (viewportLength >= 1) {
-            return {
-              hasSelection: false,
-              isModifying: false,
-            };
+            return null;
           }
           const viewportPixelWidth = containerWidth - marginLeft - marginRight;
           const unitOffsetX = offsetX * (viewportLength / viewportPixelWidth);
@@ -742,7 +735,6 @@ class ChartViewportImpl<OwnProps> extends React.PureComponent<
 
           const timeRangeLength = timeRange.end - timeRange.start;
           return {
-            hasSelection: true,
             isModifying: false,
             selectionStart: timeRange.start + timeRangeLength * newViewportLeft,
             selectionEnd: timeRange.start + timeRangeLength * newViewportRight,
diff --git a/src/components/stack-chart/Canvas.tsx b/src/components/stack-chart/Canvas.tsx
index 2cf2433a11..d158b1d7ff 100644
--- a/src/components/stack-chart/Canvas.tsx
+++ b/src/components/stack-chart/Canvas.tsx
@@ -641,7 +641,6 @@ class StackChartCanvasImpl extends React.PureComponent<Props> {
     const { depth, stackTimingIndex } = hoveredItem;
     const { combinedTimingRows, updatePreviewSelection } = this.props;
     updatePreviewSelection({
-      hasSelection: true,
       isModifying: false,
       selectionStart: combinedTimingRows[depth].start[stackTimingIndex],
       selectionEnd: combinedTimingRows[depth].end[stackTimingIndex],
diff --git a/src/components/stack-chart/index.tsx b/src/components/stack-chart/index.tsx
index 7821773da6..d2fdf4fa5e 100644
--- a/src/components/stack-chart/index.tsx
+++ b/src/components/stack-chart/index.tsx
@@ -72,7 +72,7 @@ type StateProps = {
   readonly sameWidthsIndexToTimestampMap: SameWidthsIndexToTimestampMap;
   readonly timeRange: StartEndRange;
   readonly interval: Milliseconds;
-  readonly previewSelection: PreviewSelection;
+  readonly previewSelection: PreviewSelection | null;
   readonly threadsKey: ThreadsKey;
   readonly callNodeInfo: CallNodeInfo;
   readonly categories: CategoryList;
diff --git a/src/components/timeline/Markers.tsx b/src/components/timeline/Markers.tsx
index 271cdf71ef..0a37b550f5 100644
--- a/src/components/timeline/Markers.tsx
+++ b/src/components/timeline/Markers.tsx
@@ -14,7 +14,7 @@ import { Tooltip } from 'firefox-profiler/components/tooltip/Tooltip';
 import { TooltipMarker } from 'firefox-profiler/components/tooltip/Marker';
 import { timeCode } from 'firefox-profiler/utils/time-code';
 import explicitConnect from 'firefox-profiler/utils/connect';
-import { getPreviewSelection } from 'firefox-profiler/selectors/profile';
+import { getPreviewSelectionIsBeingModified } from 'firefox-profiler/selectors/profile';
 import { getThreadSelectorsFromThreadsKey } from 'firefox-profiler/selectors/per-thread';
 import { getSelectedThreadIndexes } from 'firefox-profiler/selectors/url-state';
 import { changeRightClickedMarker } from 'firefox-profiler/actions/profile-view';
@@ -528,7 +528,7 @@ export const TimelineMarkersJank = explicitConnect<
       // These don't use marker schema as they are derived.
       markerIndexes: selectors.getTimelineJankMarkerIndexes(state),
       isSelected: _getTimelineMarkersIsSelected(selectedThreads, threadsKey),
-      isModifyingSelection: getPreviewSelection(state).isModifying,
+      isModifyingSelection: getPreviewSelectionIsBeingModified(state),
       testId: 'TimelineMarkersJank',
       rightClickedMarker: selectors.getRightClickedMarker(state),
     };
@@ -557,7 +557,7 @@ export const TimelineMarkersOverview = explicitConnect<
       getMarker: selectors.getMarkerGetter(state),
       markerIndexes: selectors.getTimelineOverviewMarkerIndexes(state),
       isSelected: _getTimelineMarkersIsSelected(selectedThreads, threadsKey),
-      isModifyingSelection: getPreviewSelection(state).isModifying,
+      isModifyingSelection: getPreviewSelectionIsBeingModified(state),
       testId: 'TimelineMarkersOverview',
       rightClickedMarker: selectors.getRightClickedMarker(state),
     };
@@ -583,7 +583,7 @@ export const TimelineMarkersFileIo = explicitConnect<
       getMarker: selectors.getMarkerGetter(state),
       markerIndexes: selectors.getTimelineFileIoMarkerIndexes(state),
       isSelected: _getTimelineMarkersIsSelected(selectedThreads, threadsKey),
-      isModifyingSelection: getPreviewSelection(state).isModifying,
+      isModifyingSelection: getPreviewSelectionIsBeingModified(state),
       testId: 'TimelineMarkersFileIo',
       rightClickedMarker: selectors.getRightClickedMarker(state),
     };
@@ -609,7 +609,7 @@ export const TimelineMarkersMemory = explicitConnect<
       getMarker: selectors.getMarkerGetter(state),
       markerIndexes: selectors.getTimelineMemoryMarkerIndexes(state),
       isSelected: _getTimelineMarkersIsSelected(selectedThreads, threadsKey),
-      isModifyingSelection: getPreviewSelection(state).isModifying,
+      isModifyingSelection: getPreviewSelectionIsBeingModified(state),
       additionalClassName: 'timelineMarkersMemory',
       testId: 'TimelineMarkersMemory',
       rightClickedMarker: selectors.getRightClickedMarker(state),
@@ -636,7 +636,7 @@ export const TimelineMarkersIPC = explicitConnect<
       getMarker: selectors.getMarkerGetter(state),
       markerIndexes: selectors.getTimelineIPCMarkerIndexes(state),
       isSelected: _getTimelineMarkersIsSelected(selectedThreads, threadsKey),
-      isModifyingSelection: getPreviewSelection(state).isModifying,
+      isModifyingSelection: getPreviewSelectionIsBeingModified(state),
       additionalClassName: 'timelineMarkersIPC',
       testId: 'TimelineMarkersIPC',
       rightClickedMarker: selectors.getRightClickedMarker(state),
diff --git a/src/components/timeline/Selection.tsx b/src/components/timeline/Selection.tsx
index f1b7ef5caa..f7a56fd5bf 100644
--- a/src/components/timeline/Selection.tsx
+++ b/src/components/timeline/Selection.tsx
@@ -41,7 +41,7 @@ type OwnProps = {
 };
 
 type StateProps = {
-  readonly previewSelection: PreviewSelection;
+  readonly previewSelection: PreviewSelection | null;
   readonly committedRange: StartEndRange;
   readonly zeroAt: Milliseconds;
   readonly profileTimelineUnit: string;
@@ -139,10 +139,9 @@ class TimelineRulerAndSelection extends React.PureComponent<Props> {
         isRangeSelecting = false;
         this._uninstallMoveAndClickHandlers();
 
-        if (previewSelection.hasSelection) {
+        if (previewSelection) {
           const { selectionStart, selectionEnd } = previewSelection;
           this.props.updatePreviewSelection({
-            hasSelection: true,
             selectionStart,
             selectionEnd,
             isModifying: false,
@@ -158,7 +157,6 @@ class TimelineRulerAndSelection extends React.PureComponent<Props> {
         isRangeSelecting = true;
         const { selectionStart, selectionEnd } = getSelectionFromEvent(event);
         this.props.updatePreviewSelection({
-          hasSelection: true,
           selectionStart,
           selectionEnd,
           isModifying: true,
@@ -171,7 +169,6 @@ class TimelineRulerAndSelection extends React.PureComponent<Props> {
         // This click ends the current selection gesture.
         const { selectionStart, selectionEnd } = getSelectionFromEvent(event);
         this.props.updatePreviewSelection({
-          hasSelection: true,
           selectionStart,
           selectionEnd,
           isModifying: false,
@@ -187,7 +184,7 @@ class TimelineRulerAndSelection extends React.PureComponent<Props> {
       // there may be one from a previous selection operation).
 
       const { previewSelection } = this.props;
-      if (previewSelection.hasSelection) {
+      if (previewSelection) {
         // There's a selection.
         // Dismiss it but only if the click is outside the current selection.
         const clickTime =
@@ -201,10 +198,7 @@ class TimelineRulerAndSelection extends React.PureComponent<Props> {
           event.stopPropagation();
 
           // Unset preview selection.
-          this.props.updatePreviewSelection({
-            hasSelection: false,
-            isModifying: false,
-          });
+          this.props.updatePreviewSelection(null);
         }
       }
 
@@ -270,45 +264,55 @@ class TimelineRulerAndSelection extends React.PureComponent<Props> {
     this.props.changeMouseTimePosition(null);
   };
 
-  _makeOnMove =
-    (fun: (dx: number) => { startDelta: number; endDelta: number }) =>
-    (
-      originalSelection: {
-        readonly selectionStart: number;
-        readonly selectionEnd: number;
-      },
+  _makeOnMove = (
+    fun: (dx: number) => { startDelta: number; endDelta: number }
+  ) => {
+    return (
+      originalSelection: PreviewSelection,
       dx: number,
-      dy: number,
+      _dy: number,
       isModifying: boolean
     ) => {
-      const { committedRange, width, updatePreviewSelection } = this.props;
-      const delta = (dx / width) * (committedRange.end - committedRange.start);
-      const selectionDeltas = fun(delta);
-      let selectionStart = clamp(
-        originalSelection.selectionStart + selectionDeltas.startDelta,
-        committedRange.start,
-        committedRange.end
-      );
-      let selectionEnd = clamp(
-        originalSelection.selectionEnd + selectionDeltas.endDelta,
-        committedRange.start,
-        committedRange.end
-      );
-      let draggingStart = isModifying && !!selectionDeltas.startDelta;
-      let draggingEnd = isModifying && !!selectionDeltas.endDelta;
-      if (selectionStart > selectionEnd) {
-        [selectionStart, selectionEnd] = [selectionEnd, selectionStart];
-        [draggingStart, draggingEnd] = [draggingEnd, draggingStart];
-      }
-      updatePreviewSelection({
-        hasSelection: true,
-        isModifying,
-        selectionStart,
-        selectionEnd,
-        draggingStart,
-        draggingEnd,
-      });
+      this._onMove(originalSelection, fun, dx, isModifying);
     };
+  };
+
+  _onMove(
+    originalSelection: PreviewSelection,
+    selectionDeltasForDx: (dx: number) => {
+      startDelta: number;
+      endDelta: number;
+    },
+    dx: number,
+    isModifying: boolean
+  ) {
+    const { committedRange, width, updatePreviewSelection } = this.props;
+    const delta = (dx / width) * (committedRange.end - committedRange.start);
+    const selectionDeltas = selectionDeltasForDx(delta);
+    let selectionStart = clamp(
+      originalSelection.selectionStart + selectionDeltas.startDelta,
+      committedRange.start,
+      committedRange.end
+    );
+    let selectionEnd = clamp(
+      originalSelection.selectionEnd + selectionDeltas.endDelta,
+      committedRange.start,
+      committedRange.end
+    );
+    let draggingStart = isModifying && !!selectionDeltas.startDelta;
+    let draggingEnd = isModifying && !!selectionDeltas.endDelta;
+    if (selectionStart > selectionEnd) {
+      [selectionStart, selectionEnd] = [selectionEnd, selectionStart];
+      [draggingStart, draggingEnd] = [draggingEnd, draggingStart];
+    }
+    updatePreviewSelection({
+      isModifying,
+      selectionStart,
+      selectionEnd,
+      draggingStart,
+      draggingEnd,
+    });
+  }
 
   _rangeStartOnMove = this._makeOnMove((delta) => ({
     startDelta: delta,
@@ -332,7 +336,7 @@ class TimelineRulerAndSelection extends React.PureComponent<Props> {
   _zoomButtonOnClick = (e: React.MouseEvent<HTMLElement>) => {
     e.stopPropagation();
     const { previewSelection, zeroAt, commitRange } = this.props;
-    if (previewSelection.hasSelection) {
+    if (previewSelection) {
       commitRange(
         previewSelection.selectionStart - zeroAt,
         previewSelection.selectionEnd - zeroAt
@@ -340,13 +344,7 @@ class TimelineRulerAndSelection extends React.PureComponent<Props> {
     }
   };
 
-  renderSelectionOverlay(previewSelection: {
-    readonly selectionStart: number;
-    readonly selectionEnd: number;
-    readonly isModifying: boolean;
-    readonly draggingStart?: boolean;
-    readonly draggingEnd?: boolean;
-  }) {
+  renderSelectionOverlay(previewSelection: PreviewSelection) {
     const { committedRange, width, profileTimelineUnit } = this.props;
     const { selectionStart, selectionEnd } = previewSelection;
 
@@ -464,14 +462,14 @@ class TimelineRulerAndSelection extends React.PureComponent<Props> {
         onMouseLeave={this._onMouseLeave}
       >
         {children}
-        {previewSelection.hasSelection
+        {previewSelection
           ? this.renderSelectionOverlay(previewSelection)
           : null}
         <div
           className="timelineSelectionHoverLine"
           style={{
             visibility:
-              previewSelection.isModifying ||
+              previewSelection?.isModifying ||
               hoverLocation === null ||
               isNaN(hoverLocation)
                 ? 'hidden'
diff --git a/src/components/timeline/TrackBandwidthGraph.tsx b/src/components/timeline/TrackBandwidthGraph.tsx
index 6de3fa698d..6f05c80bd2 100644
--- a/src/components/timeline/TrackBandwidthGraph.tsx
+++ b/src/components/timeline/TrackBandwidthGraph.tsx
@@ -316,7 +316,7 @@ type StateProps = {
   readonly interval: Milliseconds;
   readonly filteredThread: Thread;
   readonly unfilteredSamplesRange: StartEndRange | null;
-  readonly previewSelection: PreviewSelection;
+  readonly previewSelection: PreviewSelection | null;
 };
 
 type DispatchProps = {};
@@ -509,7 +509,7 @@ class TrackBandwidthGraphImpl extends React.PureComponent<Props, State> {
     const unitGraphCount = samples.count[counterIndex] / sampleTimeDeltaInMs;
 
     let rangeTotal = 0;
-    if (previewSelection.hasSelection) {
+    if (previewSelection) {
       const [beginIndex, endIndex] = getSampleIndexRangeForSelection(
         samples,
         previewSelection.selectionStart,
@@ -556,7 +556,7 @@ class TrackBandwidthGraphImpl extends React.PureComponent<Props, State> {
               countRange,
               'TrackBandwidthGraph--total-bandwidth-in-graph'
             )}
-            {previewSelection.hasSelection
+            {previewSelection
               ? this._formatDataTransferValue(
                   rangeTotal,
                   'TrackBandwidthGraph--total-bandwidth-in-range'
diff --git a/src/components/timeline/TrackIPC.tsx b/src/components/timeline/TrackIPC.tsx
index 569b79f096..b2e49c6fe2 100644
--- a/src/components/timeline/TrackIPC.tsx
+++ b/src/components/timeline/TrackIPC.tsx
@@ -39,7 +39,6 @@ export class TrackIPCImpl extends React.PureComponent<Props, State> {
   _onMarkerSelect = (start: Milliseconds, end: Milliseconds) => {
     const { rangeStart, rangeEnd, updatePreviewSelection } = this.props;
     updatePreviewSelection({
-      hasSelection: true,
       isModifying: false,
       selectionStart: Math.max(rangeStart, start),
       selectionEnd: Math.min(rangeEnd, end),
diff --git a/src/components/timeline/TrackMemory.tsx b/src/components/timeline/TrackMemory.tsx
index fee25ea67d..7c0dc3cf00 100644
--- a/src/components/timeline/TrackMemory.tsx
+++ b/src/components/timeline/TrackMemory.tsx
@@ -49,7 +49,6 @@ export class TrackMemoryImpl extends React.PureComponent<Props, State> {
   _onMarkerSelect = (start: Milliseconds, end: Milliseconds) => {
     const { rangeStart, rangeEnd, updatePreviewSelection } = this.props;
     updatePreviewSelection({
-      hasSelection: true,
       isModifying: false,
       selectionStart: Math.max(rangeStart, start),
       selectionEnd: Math.min(rangeEnd, end),
diff --git a/src/components/timeline/TrackNetwork.tsx b/src/components/timeline/TrackNetwork.tsx
index 4cd94503e9..c2ff5083e4 100644
--- a/src/components/timeline/TrackNetwork.tsx
+++ b/src/components/timeline/TrackNetwork.tsx
@@ -14,7 +14,7 @@ import {
   getCommittedRange,
   getZeroAt,
   getInnerWindowIDToPageMap,
-  getPreviewSelection,
+  getPreviewSelectionIsBeingModified,
 } from 'firefox-profiler/selectors/profile';
 import { getThreadSelectors } from 'firefox-profiler/selectors/per-thread';
 import {
@@ -432,7 +432,7 @@ export const TrackNetwork = explicitConnect<
       rangeStart: start,
       rangeEnd: end,
       zeroAt: getZeroAt(state),
-      isModifyingSelection: getPreviewSelection(state).isModifying,
+      isModifyingSelection: getPreviewSelectionIsBeingModified(state),
       verticalMarkerIndexes: selectors.getTimelineVerticalMarkerIndexes(state),
       rightClickedMarkerIndex: selectors.getRightClickedMarkerIndex(state),
       selectedNetworkMarkerIndex:
diff --git a/src/components/timeline/TrackScreenshots.tsx b/src/components/timeline/TrackScreenshots.tsx
index 1eef18ed38..4ec906de4e 100644
--- a/src/components/timeline/TrackScreenshots.tsx
+++ b/src/components/timeline/TrackScreenshots.tsx
@@ -6,7 +6,7 @@ import { PureComponent } from 'react';
 import explicitConnect from 'firefox-profiler/utils/connect';
 import {
   getCommittedRange,
-  getPreviewSelection,
+  getPreviewSelectionIsBeingModified,
 } from 'firefox-profiler/selectors/profile';
 import { getThreadSelectors } from 'firefox-profiler/selectors/per-thread';
 import {
@@ -117,7 +117,6 @@ class Screenshots extends PureComponent<Props, State> {
       return;
     }
     updatePreviewSelection({
-      hasSelection: true,
       isModifying: false,
       selectionStart: start,
       selectionEnd: end,
@@ -190,7 +189,6 @@ export const TimelineTrackScreenshots = explicitConnect<
     const { threadIndex, windowId } = ownProps;
     const selectors = getThreadSelectors(threadIndex);
     const { start, end } = getCommittedRange(state);
-    const previewSelection = getPreviewSelection(state);
     return {
       thread: selectors.getRangeFilteredThread(state),
       screenshots:
@@ -199,8 +197,7 @@ export const TimelineTrackScreenshots = explicitConnect<
       threadName: selectors.getFriendlyThreadName(state),
       rangeStart: start,
       rangeEnd: end,
-      isMakingPreviewSelection:
-        previewSelection.hasSelection && previewSelection.isModifying,
+      isMakingPreviewSelection: getPreviewSelectionIsBeingModified(state),
     };
   },
   mapDispatchToProps: {
diff --git a/src/components/timeline/TrackThread.tsx b/src/components/timeline/TrackThread.tsx
index cc7068d193..a69c91c07e 100644
--- a/src/components/timeline/TrackThread.tsx
+++ b/src/components/timeline/TrackThread.tsx
@@ -153,7 +153,6 @@ class TimelineTrackThreadImpl extends PureComponent<Props> {
   _onMarkerSelect = (start: Milliseconds, end: Milliseconds) => {
     const { rangeStart, rangeEnd, updatePreviewSelection } = this.props;
     updatePreviewSelection({
-      hasSelection: true,
       isModifying: false,
       selectionStart: Math.max(rangeStart, start),
       selectionEnd: Math.min(rangeEnd, end),
diff --git a/src/components/tooltip/TrackPower.tsx b/src/components/tooltip/TrackPower.tsx
index b0490e12d4..062abd0aab 100644
--- a/src/components/tooltip/TrackPower.tsx
+++ b/src/components/tooltip/TrackPower.tsx
@@ -38,7 +38,7 @@ type StateProps = {
   interval: Milliseconds;
   meta: ProfileMeta;
   committedRange: StartEndRange;
-  previewSelection: PreviewSelection;
+  previewSelection: PreviewSelection | null;
 };
 
 type Props = ConnectedProps<OwnProps, StateProps, {}>;
@@ -123,9 +123,9 @@ class TooltipTrackPowerImpl extends React.PureComponent<Props> {
   }
 
   maybeRenderForPreviewSelection(
-    previewSelection: PreviewSelection
+    previewSelection: PreviewSelection | null
   ): React.ReactElement<any> | null {
-    if (!previewSelection.hasSelection) {
+    if (!previewSelection) {
       return null;
     }
 
diff --git a/src/reducers/profile-view.ts b/src/reducers/profile-view.ts
index 68ac0fc71e..6039d1f810 100644
--- a/src/reducers/profile-view.ts
+++ b/src/reducers/profile-view.ts
@@ -529,21 +529,20 @@ const waitingForLibs: Reducer<Set<RequestedLib>> = (
   }
 };
 
-const previewSelection: Reducer<PreviewSelection> = (
-  state = { hasSelection: false, isModifying: false },
+const previewSelection: Reducer<PreviewSelection | null> = (
+  state = null,
   action
 ) => {
   switch (action.type) {
     case 'UPDATE_PREVIEW_SELECTION':
       return action.previewSelection;
     case 'COMMIT_RANGE':
-      return { hasSelection: false, isModifying: false };
+      return null;
     case 'POP_COMMITTED_RANGES':
       if (!action.committedRange) {
-        return { hasSelection: false, isModifying: false };
+        return null;
       }
       return {
-        hasSelection: true,
         isModifying: false,
         selectionStart: action.committedRange.start,
         selectionEnd: action.committedRange.end,
diff --git a/src/selectors/per-thread/markers.ts b/src/selectors/per-thread/markers.ts
index 59a9ab4d7a..7f8bf72048 100644
--- a/src/selectors/per-thread/markers.ts
+++ b/src/selectors/per-thread/markers.ts
@@ -279,7 +279,7 @@ export function getMarkerSelectorsPerThread(
       getSearchFilteredMarkerIndexes,
       ProfileSelectors.getPreviewSelection,
       (getMarker, markerIndexes, previewSelection) => {
-        if (!previewSelection.hasSelection) {
+        if (!previewSelection) {
           return markerIndexes;
         }
         const { selectionStart, selectionEnd } = previewSelection;
diff --git a/src/selectors/per-thread/thread.tsx b/src/selectors/per-thread/thread.tsx
index bf1eff56c6..30a939f7c1 100644
--- a/src/selectors/per-thread/thread.tsx
+++ b/src/selectors/per-thread/thread.tsx
@@ -473,7 +473,7 @@ export function getThreadSelectorsWithMarkersPerThread(
     getFilteredThread,
     ProfileSelectors.getPreviewSelection,
     (thread, previewSelection): Thread => {
-      if (!previewSelection.hasSelection) {
+      if (!previewSelection) {
         return thread;
       }
       const { selectionStart, selectionEnd } = previewSelection;
@@ -521,7 +521,7 @@ export function getThreadSelectorsWithMarkersPerThread(
       ProfileSelectors.getPreviewSelection,
       threadSelectors.getFilteredCtssSampleIndexOffset,
       (samples, previewSelection, sampleIndexFromCommittedRange) => {
-        if (!previewSelection.hasSelection) {
+        if (!previewSelection) {
           return sampleIndexFromCommittedRange;
         }
 
diff --git a/src/selectors/profile.ts b/src/selectors/profile.ts
index 60d06fe102..791dac37b8 100644
--- a/src/selectors/profile.ts
+++ b/src/selectors/profile.ts
@@ -137,9 +137,16 @@ export const getTableViewOptionSelectors: (
   return options || defaultTableViewOptions;
 };
 
-export const getPreviewSelection: Selector<PreviewSelection> = (state) =>
+export const getPreviewSelection: Selector<PreviewSelection | null> = (state) =>
   getProfileViewOptions(state).previewSelection;
 
+export const getPreviewSelectionIsBeingModified: Selector<boolean> = (
+  state
+) => {
+  const previewSelection = getPreviewSelection(state);
+  return previewSelection ? previewSelection.isModifying : false;
+};
+
 /**
  * This selector returns the current range, taking into account the current
  * preview selection if any.
@@ -148,7 +155,7 @@ export const getPreviewSelectionRange: Selector<StartEndRange> = createSelector(
   getCommittedRange,
   getPreviewSelection,
   (committedRange, previewSelection) => {
-    if (previewSelection.hasSelection) {
+    if (previewSelection) {
       return {
         start: previewSelection.selectionStart,
         end: previewSelection.selectionEnd,
diff --git a/src/test/components/FilterNavigatorBar.test.tsx b/src/test/components/FilterNavigatorBar.test.tsx
index 3b797a7316..b572bddc12 100644
--- a/src/test/components/FilterNavigatorBar.test.tsx
+++ b/src/test/components/FilterNavigatorBar.test.tsx
@@ -115,7 +115,6 @@ describe('app/ProfileFilterNavigator', () => {
     act(() => {
       dispatch(
         ProfileView.updatePreviewSelection({
-          hasSelection: true,
           isModifying: false,
           selectionStart: 10,
           selectionEnd: 10.1,
diff --git a/src/test/components/FlameGraph.test.tsx b/src/test/components/FlameGraph.test.tsx
index 21fd7ec37f..4b3bcf514e 100644
--- a/src/test/components/FlameGraph.test.tsx
+++ b/src/test/components/FlameGraph.test.tsx
@@ -201,7 +201,6 @@ describe('FlameGraph', function () {
     act(() => {
       dispatch(
         updatePreviewSelection({
-          hasSelection: true,
           isModifying: false,
           selectionStart: 1.3,
           selectionEnd: 5,
@@ -246,7 +245,6 @@ describe('FlameGraph', function () {
       act(() => {
         dispatch(
           updatePreviewSelection({
-            hasSelection: true,
             isModifying: false,
             selectionStart: 5,
             selectionEnd: 10,
diff --git a/src/test/components/MarkerChart.test.tsx b/src/test/components/MarkerChart.test.tsx
index ab4f24645f..cb63c1df6f 100644
--- a/src/test/components/MarkerChart.test.tsx
+++ b/src/test/components/MarkerChart.test.tsx
@@ -650,7 +650,6 @@ describe('MarkerChart', function () {
 
       clickOnMenuItem(/start.*start/i);
       expect(getPreviewSelection(getState())).toEqual({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 2,
         selectionEnd: 11,
@@ -658,7 +657,6 @@ describe('MarkerChart', function () {
 
       clickOnMenuItem(/start.*end/i);
       expect(getPreviewSelection(getState())).toEqual({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 8,
         selectionEnd: 11,
@@ -667,7 +665,6 @@ describe('MarkerChart', function () {
       // This one doesn't work because it's disabled.
       clickOnMenuItem(/end.*start/i);
       expect(getPreviewSelection(getState())).toEqual({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 8,
         selectionEnd: 11,
@@ -677,7 +674,6 @@ describe('MarkerChart', function () {
       rightClick(findFillTextPosition('UserTiming A'));
       clickOnMenuItem(/start.*start/i);
       expect(getPreviewSelection(getState())).toEqual({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 0,
         selectionEnd: 11,
@@ -687,7 +683,6 @@ describe('MarkerChart', function () {
 
       clickOnMenuItem(/end.*start/i);
       expect(getPreviewSelection(getState())).toEqual({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 0,
         selectionEnd: 2,
@@ -695,7 +690,6 @@ describe('MarkerChart', function () {
 
       clickOnMenuItem(/end.*end/i);
       expect(getPreviewSelection(getState())).toEqual({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 0,
         selectionEnd: 8,
@@ -710,7 +704,6 @@ describe('MarkerChart', function () {
       rightClick(findFillTextPosition('UserTiming B'));
       clickOnMenuItem(/duration/);
       expect(getPreviewSelection(getState())).toEqual({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 2,
         selectionEnd: 8,
@@ -719,7 +712,6 @@ describe('MarkerChart', function () {
       rightClick(findFillTextPosition('UserTiming A'));
       clickOnMenuItem(/duration/);
       expect(getPreviewSelection(getState())).toEqual({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 0,
         selectionEnd: 10,
diff --git a/src/test/components/MarkerTable.test.tsx b/src/test/components/MarkerTable.test.tsx
index dc1fb9a408..2d381ff82a 100644
--- a/src/test/components/MarkerTable.test.tsx
+++ b/src/test/components/MarkerTable.test.tsx
@@ -99,7 +99,6 @@ describe('MarkerTable', function () {
     act(() => {
       dispatch(
         updatePreviewSelection({
-          hasSelection: true,
           isModifying: false,
           selectionStart: 10,
           selectionEnd: 20,
diff --git a/src/test/components/NetworkChart.test.tsx b/src/test/components/NetworkChart.test.tsx
index 7cd74e9b37..ffc6d3512b 100644
--- a/src/test/components/NetworkChart.test.tsx
+++ b/src/test/components/NetworkChart.test.tsx
@@ -288,7 +288,6 @@ describe('NetworkChartRowBar phase calculations', function () {
     act(() => {
       dispatch(
         updatePreviewSelection({
-          hasSelection: true,
           isModifying: false,
           selectionStart: 20,
           selectionEnd: 40,
diff --git a/src/test/components/StackChart.test.tsx b/src/test/components/StackChart.test.tsx
index c0fe831e9a..3181a25957 100644
--- a/src/test/components/StackChart.test.tsx
+++ b/src/test/components/StackChart.test.tsx
@@ -129,7 +129,6 @@ describe('StackChart', function () {
     act(() =>
       dispatch(
         updatePreviewSelection({
-          hasSelection: true,
           isModifying: false,
           selectionStart: 3.1,
           selectionEnd: 3.4,
diff --git a/src/test/components/TrackBandwidth.test.tsx b/src/test/components/TrackBandwidth.test.tsx
index 5d5458f9e7..3f208ec09e 100644
--- a/src/test/components/TrackBandwidth.test.tsx
+++ b/src/test/components/TrackBandwidth.test.tsx
@@ -214,7 +214,6 @@ describe('TrackBandwidth', function () {
     act(() => {
       dispatch(
         updatePreviewSelection({
-          hasSelection: true,
           isModifying: false,
           selectionStart: 5,
           selectionEnd: 6,
diff --git a/src/test/components/TrackPower.test.tsx b/src/test/components/TrackPower.test.tsx
index 065bbf1cdf..402180cec9 100644
--- a/src/test/components/TrackPower.test.tsx
+++ b/src/test/components/TrackPower.test.tsx
@@ -190,7 +190,6 @@ describe('TrackPower', function () {
     const { dispatch, moveMouseAtCounter } = setup();
     dispatch(
       updatePreviewSelection({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 5,
         selectionEnd: 6,
@@ -220,7 +219,6 @@ describe('TrackPower', function () {
     const { dispatch, moveMouseAtCounter } = setup();
     dispatch(
       updatePreviewSelection({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 6,
         selectionEnd: 6,
diff --git a/src/test/components/TrackScreenshots.test.tsx b/src/test/components/TrackScreenshots.test.tsx
index ed3ae07e6e..43ccf90be8 100644
--- a/src/test/components/TrackScreenshots.test.tsx
+++ b/src/test/components/TrackScreenshots.test.tsx
@@ -88,7 +88,6 @@ describe('timeline/TrackScreenshots', function () {
     screenshotClick(LEFT);
 
     const expectedPreviewSelection = {
-      hasSelection: true,
       isModifying: false,
       selectionEnd: 1,
       selectionStart: 0,
diff --git a/src/test/components/Viewport.test.tsx b/src/test/components/Viewport.test.tsx
index 26e54a3b92..6bbf9a9c32 100644
--- a/src/test/components/Viewport.test.tsx
+++ b/src/test/components/Viewport.test.tsx
@@ -631,7 +631,7 @@ function setup(profileOverrides: MixedObject = {}) {
   };
 
   type StateProps = {
-    previewSelection: PreviewSelection;
+    previewSelection: PreviewSelection | null;
     timeRange: StartEndRange;
   };
 
diff --git a/src/test/store/actions.test.ts b/src/test/store/actions.test.ts
index 4eb46d9524..7c2b2f17c6 100644
--- a/src/test/store/actions.test.ts
+++ b/src/test/store/actions.test.ts
@@ -392,7 +392,6 @@ describe('selectors/getHasPreviewFilteredCtssSamples', function () {
 
     store.dispatch(
       updatePreviewSelection({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 1.1,
         selectionEnd: 1.7,
@@ -428,14 +427,10 @@ describe('actions/updatePreviewSelection', function () {
     const initialSelection = ProfileViewSelectors.getPreviewSelection(
       store.getState()
     );
-    expect(initialSelection).toEqual({
-      hasSelection: false,
-      isModifying: false,
-    });
+    expect(initialSelection).toBe(null);
 
     store.dispatch(
       updatePreviewSelection({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 100,
         selectionEnd: 200,
@@ -446,7 +441,6 @@ describe('actions/updatePreviewSelection', function () {
       store.getState()
     );
     expect(secondSelection).toEqual({
-      hasSelection: true,
       isModifying: false,
       selectionStart: 100,
       selectionEnd: 200,
diff --git a/src/test/store/profile-view.test.ts b/src/test/store/profile-view.test.ts
index f2c53d5b7c..bb3651313c 100644
--- a/src/test/store/profile-view.test.ts
+++ b/src/test/store/profile-view.test.ts
@@ -1464,20 +1464,15 @@ describe('actions/ProfileView', function () {
       const { profile } = getProfileFromTextSamples('A');
       const { dispatch, getState } = storeWithProfile(profile);
 
-      expect(ProfileViewSelectors.getPreviewSelection(getState())).toEqual({
-        hasSelection: false,
-        isModifying: false,
-      });
+      expect(ProfileViewSelectors.getPreviewSelection(getState())).toBe(null);
       dispatch(
         ProfileView.updatePreviewSelection({
-          hasSelection: true,
           isModifying: false,
           selectionStart: 0,
           selectionEnd: 1,
         })
       );
       expect(ProfileViewSelectors.getPreviewSelection(getState())).toEqual({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 0,
         selectionEnd: 1,
@@ -1526,7 +1521,6 @@ describe('actions/ProfileView', function () {
       dispatch(ProfileView.commitRange(0, 10));
       dispatch(
         ProfileView.updatePreviewSelection({
-          hasSelection: true,
           isModifying: false,
           selectionStart: 1,
           selectionEnd: 9,
@@ -1536,7 +1530,6 @@ describe('actions/ProfileView', function () {
         { start: 0, end: 10 },
       ]);
       expect(ProfileViewSelectors.getPreviewSelection(getState())).toEqual({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 1,
         selectionEnd: 9,
@@ -1553,10 +1546,7 @@ describe('actions/ProfileView', function () {
         { start: 0, end: 10 },
         { start: 2, end: 8 },
       ]);
-      expect(ProfileViewSelectors.getPreviewSelection(getState())).toEqual({
-        hasSelection: false,
-        isModifying: false,
-      });
+      expect(ProfileViewSelectors.getPreviewSelection(getState())).toBe(null);
       expect(ProfileViewSelectors.getPreviewSelectionRange(getState())).toEqual(
         {
           start: 2,
@@ -1596,14 +1586,12 @@ describe('actions/ProfileView', function () {
       const { getState, dispatch } = setupStore();
       dispatch(
         ProfileView.updatePreviewSelection({
-          hasSelection: true,
           isModifying: false,
           selectionStart: 1,
           selectionEnd: 9,
         })
       );
       expect(ProfileViewSelectors.getPreviewSelection(getState())).toEqual({
-        hasSelection: true,
         isModifying: false,
         selectionEnd: 9,
         selectionStart: 1,
@@ -1621,7 +1609,6 @@ describe('actions/ProfileView', function () {
         { start: 1, end: 9 },
       ]);
       expect(ProfileViewSelectors.getPreviewSelection(getState())).toEqual({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 3,
         selectionEnd: 7,
@@ -1643,17 +1630,13 @@ describe('actions/ProfileView', function () {
         { start: 1, end: 9 },
       ]);
       expect(ProfileViewSelectors.getPreviewSelection(getState())).toEqual({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 3,
         selectionEnd: 7,
       });
 
       dispatch(ProfileView.popCommittedRanges(2));
-      expect(ProfileViewSelectors.getPreviewSelection(getState())).toEqual({
-        hasSelection: false,
-        isModifying: false,
-      });
+      expect(ProfileViewSelectors.getPreviewSelection(getState())).toBe(null);
     });
   });
 
@@ -1872,7 +1855,6 @@ describe('snapshots of selectors/profile', function () {
     dispatch(ProfileView.commitRange(3, 7)); // Reminder: upper bound "7" is exclusive.
     dispatch(
       ProfileView.updatePreviewSelection({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 4,
         selectionEnd: 6,
@@ -2382,7 +2364,6 @@ describe('getTimingsForSidebar', () => {
 
       dispatch(
         ProfileView.updatePreviewSelection({
-          hasSelection: true,
           isModifying: false,
           selectionStart: 3,
           selectionEnd: 5,
@@ -2767,7 +2748,6 @@ describe('getTimingsForSidebar', () => {
 
       dispatch(
         ProfileView.updatePreviewSelection({
-          hasSelection: true,
           isModifying: false,
           selectionStart: 3,
           selectionEnd: 5,
@@ -3374,7 +3354,6 @@ describe('traced timing', function () {
       const { start, end } = previewSelection;
       dispatch(
         ProfileView.updatePreviewSelection({
-          hasSelection: true,
           isModifying: false,
           selectionStart: start,
           selectionEnd: end,
diff --git a/src/test/store/zipped-profiles.test.ts b/src/test/store/zipped-profiles.test.ts
index 70b2546fe1..aceee2a398 100644
--- a/src/test/store/zipped-profiles.test.ts
+++ b/src/test/store/zipped-profiles.test.ts
@@ -280,19 +280,15 @@ describe('profile state invalidation when switching between profiles', function
 
     // Create new copies of the selection on each assertion and change, so
     // that we are not relying on strict equality.
-    const getNoSelection = () => ({ hasSelection: false, isModifying: false });
     const getSomeSelection = () =>
       ({
-        hasSelection: true,
         isModifying: true,
         selectionStart: 0,
         selectionEnd: 10,
       }) as PreviewSelection;
 
     // It starts with no selection.
-    expect(ProfileViewSelectors.getPreviewSelection(getState())).toEqual(
-      getNoSelection()
-    );
+    expect(ProfileViewSelectors.getPreviewSelection(getState())).toBe(null);
 
     // Add a selection.
     dispatch(ProfileViewActions.updatePreviewSelection(getSomeSelection()));
@@ -303,8 +299,6 @@ describe('profile state invalidation when switching between profiles', function
     viewProfile('profile2.json');
 
     // It no longer has a selection when viewing another profile.
-    expect(ProfileViewSelectors.getPreviewSelection(getState())).toEqual(
-      getNoSelection()
-    );
+    expect(ProfileViewSelectors.getPreviewSelection(getState())).toBe(null);
   });
 });
diff --git a/src/test/unit/js-allocations.test.ts b/src/test/unit/js-allocations.test.ts
index 7a3d99e6d4..10f32e64db 100644
--- a/src/test/unit/js-allocations.test.ts
+++ b/src/test/unit/js-allocations.test.ts
@@ -154,7 +154,6 @@ describe('JS allocation call trees', function () {
     dispatch(commitRange(0, 1.5));
     dispatch(
       updatePreviewSelection({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 0,
         selectionEnd: 1,
diff --git a/src/test/unit/native-allocations.test.ts b/src/test/unit/native-allocations.test.ts
index 9ed2f2b373..ff406eeb66 100644
--- a/src/test/unit/native-allocations.test.ts
+++ b/src/test/unit/native-allocations.test.ts
@@ -226,7 +226,6 @@ describe('Native allocation call trees', function () {
     dispatch(commitRange(0, 1.5));
     dispatch(
       updatePreviewSelection({
-        hasSelection: true,
         isModifying: false,
         selectionStart: 0,
         selectionEnd: 1,
diff --git a/src/types/actions.ts b/src/types/actions.ts
index 3ea62bdd1c..ddd300f9fa 100644
--- a/src/types/actions.ts
+++ b/src/types/actions.ts
@@ -83,16 +83,13 @@ export type DataSource =
   | 'uploaded-recordings';
 
 export type TimelineType = 'stack' | 'category' | 'cpu-category';
-export type PreviewSelection =
-  | { readonly hasSelection: false; readonly isModifying: false }
-  | {
-      readonly hasSelection: true;
-      readonly isModifying: boolean;
-      readonly selectionStart: number;
-      readonly selectionEnd: number;
-      readonly draggingStart?: boolean;
-      readonly draggingEnd?: boolean;
-    };
+export type PreviewSelection = {
+  readonly isModifying: boolean;
+  readonly selectionStart: number;
+  readonly selectionEnd: number;
+  readonly draggingStart?: boolean;
+  readonly draggingEnd?: boolean;
+};
 
 /**
  * The counts for how many tracks are hidden in the timeline.
@@ -227,7 +224,7 @@ type ProfileAction =
     }
   | {
       readonly type: 'UPDATE_PREVIEW_SELECTION';
-      readonly previewSelection: PreviewSelection;
+      readonly previewSelection: PreviewSelection | null;
     }
   | {
       readonly type: 'CHANGE_SELECTED_ZIP_FILE';
diff --git a/src/types/state.ts b/src/types/state.ts
index e41079e2c3..7c35e49936 100644
--- a/src/types/state.ts
+++ b/src/types/state.ts
@@ -87,7 +87,7 @@ export type ProfileViewState = {
     perThread: ThreadViewOptionsPerThreads;
     symbolicationStatus: SymbolicationStatus;
     waitingForLibs: Set<RequestedLib>;
-    previewSelection: PreviewSelection;
+    previewSelection: PreviewSelection | null;
     scrollToSelectionGeneration: number;
     focusCallTreeGeneration: number;
     rootRange: StartEndRange;