diff --git a/web/chat/reaction-pill.react.js b/web/chat/reaction-pill.react.js
index 7eda90677..5a81f0b0b 100644
--- a/web/chat/reaction-pill.react.js
+++ b/web/chat/reaction-pill.react.js
@@ -1,48 +1,67 @@
 // @flow
 
 import classNames from 'classnames';
 import * as React from 'react';
 
 import type { ReactionInfo } from 'lib/selectors/chat-selectors.js';
 import { useNextLocalID } from 'lib/shared/message-utils.js';
 
 import { useSendReaction } from './reaction-message-utils.js';
 import css from './reaction-pill.css';
+import { useReactionTooltip } from '../utils/tooltip-action-utils.js';
+import { tooltipPositions } from '../utils/tooltip-utils.js';
+
+const availableReactionTooltipPositions = [
+  tooltipPositions.TOP,
+  tooltipPositions.BOTTOM,
+];
 
 type Props = {
   +reaction: string,
   +messageID: ?string,
   +threadID: string,
   +reactions: ReactionInfo,
 };
 
 function ReactionPill(props: Props): React.Node {
   const { reaction, messageID, threadID, reactions } = props;
 
   const localID = useNextLocalID();
   const sendReaction = useSendReaction(messageID, localID, threadID, reactions);
 
   const onClickReaction = React.useCallback(
     (event: SyntheticEvent<HTMLElement>) => {
       event.preventDefault();
       sendReaction(reaction);
     },
     [reaction, sendReaction],
   );
 
+  const { onMouseEnter, onMouseLeave } = useReactionTooltip({
+    reaction,
+    reactions,
+    availablePositions: availableReactionTooltipPositions,
+  });
+
   const reactionInfo = reactions[reaction];
   const numOfReacts = reactionInfo.users.length;
 
   const reactionClassName = classNames({
     [css.reactionContainer]: true,
     [css.reactionContainerSelected]: reactionInfo.viewerReacted,
   });
 
   return (
-    <a onClick={onClickReaction} className={reactionClassName} key={reaction}>
+    <a
+      onClick={onClickReaction}
+      onMouseEnter={onMouseEnter}
+      onMouseLeave={onMouseLeave}
+      className={reactionClassName}
+      key={reaction}
+    >
       {`${reaction} ${numOfReacts}`}
     </a>
   );
 }
 
 export default ReactionPill;
diff --git a/web/utils/tooltip-action-utils.js b/web/utils/tooltip-action-utils.js
index 345ab46ae..ed32a73f8 100644
--- a/web/utils/tooltip-action-utils.js
+++ b/web/utils/tooltip-action-utils.js
@@ -1,458 +1,506 @@
 // @flow
 
 import invariant from 'invariant';
 import * as React from 'react';
 
 import { useModalContext } from 'lib/components/modal-provider.react.js';
 import { useResettingState } from 'lib/hooks/use-resetting-state.js';
-import type { ChatMessageInfoItem } from 'lib/selectors/chat-selectors.js';
+import type {
+  ReactionInfo,
+  ChatMessageInfoItem,
+} from 'lib/selectors/chat-selectors.js';
 import { useCanEditMessage } from 'lib/shared/edit-messages-utils.js';
 import { createMessageReply } from 'lib/shared/message-utils.js';
 import { useCanCreateReactionFromMessage } from 'lib/shared/reaction-utils.js';
 import {
   threadHasPermission,
   useSidebarExistsOrCanBeCreated,
 } from 'lib/shared/thread-utils.js';
 import { messageTypes } from 'lib/types/message-types-enum.js';
 import { isComposableMessageType } from 'lib/types/message-types.js';
 import { threadPermissions } from 'lib/types/thread-permission-types.js';
 import type { ThreadInfo } from 'lib/types/thread-types.js';
 import { longAbsoluteDate } from 'lib/utils/date-utils.js';
 
 import {
   type MessageTooltipAction,
   getTooltipPositionStyle,
   calculateMessageTooltipSize,
+  calculateReactionTooltipSize,
   type TooltipPosition,
   type TooltipPositionStyle,
   type TooltipSize,
 } from './tooltip-utils.js';
 import { getComposedMessageID } from '../chat/chat-constants.js';
 import { useEditModalContext } from '../chat/edit-message-provider.js';
 import MessageTooltip from '../chat/message-tooltip.react.js';
+import ReactionTooltip from '../chat/reaction-tooltip.react.js';
 import { useTooltipContext } from '../chat/tooltip-provider.js';
 import CommIcon from '../CommIcon.react.js';
 import { InputStateContext } from '../input/input-state.js';
 import TogglePinModal from '../modals/chat/toggle-pin-modal.react.js';
 import {
   useOnClickPendingSidebar,
   useOnClickThread,
 } from '../selectors/thread-selectors.js';
 
 type UseTooltipArgs = {
   +createTooltip: (tooltipPositionStyle: TooltipPositionStyle) => React.Node,
   +tooltipSize: TooltipSize,
   +availablePositions: $ReadOnlyArray<TooltipPosition>,
   +preventDisplayingBelowSource?: boolean,
 };
 type UseTooltipResult = {
   +onMouseEnter: (event: SyntheticEvent<HTMLElement>) => mixed,
   +onMouseLeave: ?() => mixed,
 };
 
 function useTooltip({
   createTooltip,
   tooltipSize,
   availablePositions,
   preventDisplayingBelowSource,
 }: UseTooltipArgs): UseTooltipResult {
   const [onMouseLeave, setOnMouseLeave] = React.useState<?() => mixed>(null);
   const [tooltipSourcePosition, setTooltipSourcePosition] = React.useState();
 
   const { renderTooltip } = useTooltipContext();
   const updateTooltip = React.useRef();
 
   const onMouseEnter = React.useCallback(
     (event: SyntheticEvent<HTMLElement>) => {
       if (!renderTooltip) {
         return;
       }
       const rect = event.currentTarget.getBoundingClientRect();
       const { top, bottom, left, right, height, width } = rect;
       const sourcePosition = { top, bottom, left, right, height, width };
       setTooltipSourcePosition(sourcePosition);
 
       const tooltipPositionStyle = getTooltipPositionStyle({
         tooltipSourcePosition: sourcePosition,
         tooltipSize,
         availablePositions,
         preventDisplayingBelowSource,
       });
       if (!tooltipPositionStyle) {
         return;
       }
 
       const tooltip = createTooltip(tooltipPositionStyle);
 
       const renderTooltipResult = renderTooltip({
         newNode: tooltip,
         tooltipPositionStyle,
       });
       if (renderTooltipResult) {
         const { onMouseLeaveCallback: callback } = renderTooltipResult;
         setOnMouseLeave((() => callback: () => () => mixed));
         updateTooltip.current = renderTooltipResult.updateTooltip;
       }
     },
     [
       availablePositions,
       createTooltip,
       preventDisplayingBelowSource,
       renderTooltip,
       tooltipSize,
     ],
   );
 
   React.useEffect(() => {
     if (!updateTooltip.current) {
       return;
     }
 
     const tooltipPositionStyle = getTooltipPositionStyle({
       tooltipSourcePosition,
       tooltipSize,
       availablePositions,
       preventDisplayingBelowSource,
     });
     if (!tooltipPositionStyle) {
       return;
     }
 
     const tooltip = createTooltip(tooltipPositionStyle);
     updateTooltip.current?.(tooltip);
   }, [
     availablePositions,
     createTooltip,
     preventDisplayingBelowSource,
     tooltipSize,
     tooltipSourcePosition,
   ]);
 
   return {
     onMouseEnter,
     onMouseLeave,
   };
 }
 
 function useMessageTooltipSidebarAction(
   item: ChatMessageInfoItem,
   threadInfo: ThreadInfo,
 ): ?MessageTooltipAction {
   const { threadCreatedFromMessage, messageInfo } = item;
   const { popModal } = useModalContext();
   const sidebarExists = !!threadCreatedFromMessage;
   const sidebarExistsOrCanBeCreated = useSidebarExistsOrCanBeCreated(
     threadInfo,
     item,
   );
   const openThread = useOnClickThread(threadCreatedFromMessage);
   const openPendingSidebar = useOnClickPendingSidebar(messageInfo, threadInfo);
   return React.useMemo(() => {
     if (!sidebarExistsOrCanBeCreated) {
       return null;
     }
     const buttonContent = <CommIcon icon="sidebar-filled" size={16} />;
     const onClick = (event: SyntheticEvent<HTMLElement>) => {
       popModal();
 
       if (threadCreatedFromMessage) {
         openThread(event);
       } else {
         openPendingSidebar(event);
       }
     };
     return {
       actionButtonContent: buttonContent,
       onClick,
       label: sidebarExists ? 'Go to thread' : 'Create thread',
     };
   }, [
     popModal,
     openPendingSidebar,
     openThread,
     sidebarExists,
     sidebarExistsOrCanBeCreated,
     threadCreatedFromMessage,
   ]);
 }
 
 function useMessageTooltipReplyAction(
   item: ChatMessageInfoItem,
   threadInfo: ThreadInfo,
 ): ?MessageTooltipAction {
   const { messageInfo } = item;
   const { popModal } = useModalContext();
   const inputState = React.useContext(InputStateContext);
   invariant(inputState, 'inputState is required');
   const { addReply } = inputState;
   return React.useMemo(() => {
     if (
       item.messageInfo.type !== messageTypes.TEXT ||
       !threadHasPermission(threadInfo, threadPermissions.VOICED)
     ) {
       return null;
     }
     const buttonContent = <CommIcon icon="reply-filled" size={18} />;
     const onClick = () => {
       popModal();
 
       if (!messageInfo.text) {
         return;
       }
       addReply(createMessageReply(messageInfo.text));
     };
     return {
       actionButtonContent: buttonContent,
       onClick,
       label: 'Reply',
     };
   }, [popModal, addReply, item.messageInfo.type, messageInfo, threadInfo]);
 }
 
 const copiedMessageDurationMs = 2000;
 function useMessageCopyAction(
   item: ChatMessageInfoItem,
 ): ?MessageTooltipAction {
   const { messageInfo } = item;
 
   const [successful, setSuccessful] = useResettingState(
     false,
     copiedMessageDurationMs,
   );
 
   return React.useMemo(() => {
     if (messageInfo.type !== messageTypes.TEXT) {
       return null;
     }
     const buttonContent = <CommIcon icon="copy-filled" size={18} />;
     const onClick = async () => {
       try {
         await navigator.clipboard.writeText(messageInfo.text);
         setSuccessful(true);
       } catch (e) {
         setSuccessful(false);
       }
     };
     return {
       actionButtonContent: buttonContent,
       onClick,
       label: successful ? 'Copied!' : 'Copy',
     };
   }, [messageInfo.text, messageInfo.type, setSuccessful, successful]);
 }
 
 function useMessageReactAction(
   item: ChatMessageInfoItem,
   threadInfo: ThreadInfo,
 ): ?MessageTooltipAction {
   const { messageInfo } = item;
 
   const { setShouldRenderEmojiKeyboard } = useTooltipContext();
 
   const canCreateReactionFromMessage = useCanCreateReactionFromMessage(
     threadInfo,
     messageInfo,
   );
 
   return React.useMemo(() => {
     if (!canCreateReactionFromMessage) {
       return null;
     }
 
     const buttonContent = <CommIcon icon="emote-smile-filled" size={18} />;
 
     const onClickReact = () => {
       if (!setShouldRenderEmojiKeyboard) {
         return;
       }
       setShouldRenderEmojiKeyboard(true);
     };
 
     return {
       actionButtonContent: buttonContent,
       onClick: onClickReact,
       label: 'React',
     };
   }, [canCreateReactionFromMessage, setShouldRenderEmojiKeyboard]);
 }
 
 function useMessageTogglePinAction(
   item: ChatMessageInfoItem,
   threadInfo: ThreadInfo,
 ): ?MessageTooltipAction {
   const { pushModal } = useModalContext();
   const { messageInfo, isPinned } = item;
 
   const canTogglePin =
     isComposableMessageType(messageInfo.type) &&
     threadHasPermission(threadInfo, threadPermissions.MANAGE_PINS);
 
   const inputState = React.useContext(InputStateContext);
 
   return React.useMemo(() => {
     if (!canTogglePin) {
       return null;
     }
 
     const iconName = isPinned ? 'unpin' : 'pin';
 
     const buttonContent = <CommIcon icon={iconName} size={18} />;
 
     const onClickTogglePin = () => {
       pushModal(
         <InputStateContext.Provider value={inputState}>
           <TogglePinModal item={item} threadInfo={threadInfo} />
         </InputStateContext.Provider>,
       );
     };
 
     return {
       actionButtonContent: buttonContent,
       onClick: onClickTogglePin,
       label: isPinned ? 'Unpin' : 'Pin',
     };
   }, [canTogglePin, inputState, isPinned, pushModal, item, threadInfo]);
 }
 
 function useMessageEditAction(
   item: ChatMessageInfoItem,
   threadInfo: ThreadInfo,
 ): ?MessageTooltipAction {
   const { messageInfo } = item;
 
   const canEditMessage = useCanEditMessage(threadInfo, messageInfo);
   const { renderEditModal, scrollToMessage } = useEditModalContext();
   const { clearTooltip } = useTooltipContext();
 
   return React.useMemo(() => {
     if (!canEditMessage) {
       return null;
     }
     const buttonContent = <CommIcon icon="edit-filled" size={18} />;
     const onClickEdit = () => {
       const callback = (maxHeight: number) =>
         renderEditModal({
           messageInfo: item,
           threadInfo,
           isError: false,
           editedMessageDraft: messageInfo.text,
           maxHeight: maxHeight,
         });
       clearTooltip();
       scrollToMessage(getComposedMessageID(messageInfo), callback);
     };
     return {
       actionButtonContent: buttonContent,
       onClick: onClickEdit,
       label: 'Edit',
     };
   }, [
     canEditMessage,
     clearTooltip,
     item,
     messageInfo,
     renderEditModal,
     scrollToMessage,
     threadInfo,
   ]);
 }
 
 function useMessageTooltipActions(
   item: ChatMessageInfoItem,
   threadInfo: ThreadInfo,
 ): $ReadOnlyArray<MessageTooltipAction> {
   const sidebarAction = useMessageTooltipSidebarAction(item, threadInfo);
   const replyAction = useMessageTooltipReplyAction(item, threadInfo);
   const copyAction = useMessageCopyAction(item);
   const reactAction = useMessageReactAction(item, threadInfo);
   const togglePinAction = useMessageTogglePinAction(item, threadInfo);
   const editAction = useMessageEditAction(item, threadInfo);
   return React.useMemo(
     () =>
       [
         replyAction,
         sidebarAction,
         copyAction,
         reactAction,
         togglePinAction,
         editAction,
       ].filter(Boolean),
     [
       replyAction,
       sidebarAction,
       copyAction,
       reactAction,
       togglePinAction,
       editAction,
     ],
   );
 }
 
+const undefinedTooltipSize = {
+  width: 0,
+  height: 0,
+};
+
 type UseMessageTooltipArgs = {
   +availablePositions: $ReadOnlyArray<TooltipPosition>,
   +item: ChatMessageInfoItem,
   +threadInfo: ThreadInfo,
 };
 
 function useMessageTooltip({
   availablePositions,
   item,
   threadInfo,
 }: UseMessageTooltipArgs): UseTooltipResult {
   const tooltipActions = useMessageTooltipActions(item, threadInfo);
 
   const containsInlineEngagement = !!item.threadCreatedFromMessage;
 
   const messageTimestamp = React.useMemo(() => {
     const time = item.messageInfo.time;
     return longAbsoluteDate(time);
   }, [item.messageInfo.time]);
 
   const tooltipSize = React.useMemo(() => {
     if (typeof document === 'undefined') {
-      return {
-        width: 0,
-        height: 0,
-      };
+      return undefinedTooltipSize;
     }
     const tooltipLabels = tooltipActions.map(action => action.label);
     return calculateMessageTooltipSize({
       tooltipLabels,
       timestamp: messageTimestamp,
     });
   }, [messageTimestamp, tooltipActions]);
 
   const createMessageTooltip = React.useCallback(
     tooltipPositionStyle => (
       <MessageTooltip
         actions={tooltipActions}
         messageTimestamp={messageTimestamp}
         tooltipPositionStyle={tooltipPositionStyle}
         tooltipSize={tooltipSize}
         item={item}
         threadInfo={threadInfo}
       />
     ),
     [item, messageTimestamp, threadInfo, tooltipActions, tooltipSize],
   );
 
   const { onMouseEnter, onMouseLeave } = useTooltip({
     createTooltip: createMessageTooltip,
     tooltipSize,
     availablePositions,
     preventDisplayingBelowSource: containsInlineEngagement,
   });
 
   return {
     onMouseEnter,
     onMouseLeave,
   };
 }
 
+type UseReactionTooltipArgs = {
+  +reaction: string,
+  +reactions: ReactionInfo,
+  +availablePositions: $ReadOnlyArray<TooltipPosition>,
+};
+
+function useReactionTooltip({
+  reaction,
+  reactions,
+  availablePositions,
+}: UseReactionTooltipArgs): UseTooltipResult {
+  const { users } = reactions[reaction];
+
+  const tooltipSize = React.useMemo(() => {
+    if (typeof document === 'undefined') {
+      return undefinedTooltipSize;
+    }
+
+    const usernames = users.map(user => user.username).filter(Boolean);
+
+    return calculateReactionTooltipSize(usernames);
+  }, [users]);
+
+  const createReactionTooltip = React.useCallback(
+    () => <ReactionTooltip reactions={reactions} reaction={reaction} />,
+    [reaction, reactions],
+  );
+
+  const { onMouseEnter, onMouseLeave } = useTooltip({
+    createTooltip: createReactionTooltip,
+    tooltipSize,
+    availablePositions,
+  });
+
+  return {
+    onMouseEnter,
+    onMouseLeave,
+  };
+}
+
 export {
   useMessageTooltipSidebarAction,
   useMessageTooltipReplyAction,
   useMessageReactAction,
   useMessageTooltipActions,
   useMessageTooltip,
+  useReactionTooltip,
 };