diff --git a/docs/APP_REFACTORING_DESIGN.md b/docs/APP_REFACTORING_DESIGN.md
index 83e7d3c..a7b8fb4 100644
--- a/docs/APP_REFACTORING_DESIGN.md
+++ b/docs/APP_REFACTORING_DESIGN.md
@@ -80,7 +80,7 @@ To refactor `app.tsx` safely and maintain continuous code correctness, we will m
 ### Step-by-Step Execution Plan
 
 #### Phase 1: Pure Component and Utility Extraction
-*   [ ] **Step 1.1:** Create `src/components/error_display.tsx` and move `ErrorMessage` and `ErrorPopup` from `src/app.tsx`. Update imports in `src/app.tsx`.
+*   [x] **Step 1.1:** Create `src/components/error_display.tsx` and move `ErrorMessage` and `ErrorPopup` from `src/app.tsx`. Update imports in `src/app.tsx`.
 *   [ ] **Step 1.2:** Create `src/datasource/instances.ts` and move data source class instantiations. Update references in `src/app.tsx`. Refactor `EmbeddedDataSource` to clean up its message event listener when the loading promise resolves or rejects (or track listener state) to prevent duplicate event listener leaks on multiple page mounts.
 *   [ ] **Step 1.3:** Create `src/util/url_args.ts` (the parsing utility) and `src/util/url_args.spec.ts` (its Jest unit test suite) together. Extract URL query parameter parsing functions and types from `src/app.tsx`, write comprehensive tests, update imports in `src/app.tsx`, and run `npm test` to verify.
 *   [ ] **Step 1.4:** Modify `src/menu/top_bar.tsx` to make chart-specific props and event handlers optional (e.g. `data`, `allowAllRelativesChart`, `allowPrintAndDownload`, `eventHandlers`, etc.), preparing the component for rendering on the landing screen without dummy properties.
diff --git a/src/app.tsx b/src/app.tsx
index 4057ff4..cced8e9 100644
--- a/src/app.tsx
+++ b/src/app.tsx
@@ -1,15 +1,9 @@
 import * as H from 'history';
 import queryString from 'query-string';
 import {useCallback, useEffect, useMemo, useRef, useState} from 'react';
-import {FormattedMessage, useIntl} from 'react-intl';
+import {useIntl} from 'react-intl';
 import {Navigate, Route, Routes, useLocation, useNavigate} from 'react-router';
-import {
-  Loader,
-  Message,
-  Portal,
-  SidebarPushable,
-  SidebarPusher,
-} from 'semantic-ui-react';
+import {Loader, SidebarPushable, SidebarPusher} from 'semantic-ui-react';
 import {IndiInfo} from 'topola';
 import {
   Chart,
@@ -19,6 +13,7 @@ import {
   downloadSvg,
   printChart,
 } from './chart';
+import {ErrorMessage, ErrorPopup} from './components/error_display';
 import {DataSourceEnum, SourceSelection} from './datasource/data_source';
 import {EmbeddedDataSource, EmbeddedSourceSpec} from './datasource/embedded';
 import {
@@ -87,43 +82,6 @@ function getStaticUrl(): string | undefined {
 
 const staticUrl = getStaticUrl();
 
-/** Shows an error message in the middle of the screen. */
-function ErrorMessage(props: {message?: string}) {
-  return (
-    <Message negative className="error">
-      <Message.Header>
-        <FormattedMessage
-          id="error.failed_to_load_file"
-          defaultMessage={'Failed to load file'}
-        />
-      </Message.Header>
-      <p>{props.message}</p>
-    </Message>
-  );
-}
-
-interface ErrorPopupProps {
-  message?: string;
-  open: boolean;
-  onDismiss: () => void;
-}
-
-/**
- * Shows a dismissable error message in the bottom left corner of the screen.
- */
-function ErrorPopup(props: ErrorPopupProps) {
-  return (
-    <Portal open={props.open} onClose={props.onDismiss}>
-      <Message negative className="errorPopup" onDismiss={props.onDismiss}>
-        <Message.Header>
-          <FormattedMessage id="error.error" defaultMessage={'Error'} />
-        </Message.Header>
-        <p>{props.message}</p>
-      </Message>
-    </Portal>
-  );
-}
-
 enum AppState {
   INITIAL,
   LOADING,
diff --git a/src/components/error_display.tsx b/src/components/error_display.tsx
new file mode 100644
index 0000000..643e933
--- /dev/null
+++ b/src/components/error_display.tsx
@@ -0,0 +1,39 @@
+import {FormattedMessage} from 'react-intl';
+import {Message, Portal} from 'semantic-ui-react';
+
+/** Shows an error message in the middle of the screen. */
+export function ErrorMessage(props: {message?: string}) {
+  return (
+    <Message negative className="error">
+      <Message.Header>
+        <FormattedMessage
+          id="error.failed_to_load_file"
+          defaultMessage={'Failed to load file'}
+        />
+      </Message.Header>
+      <p>{props.message}</p>
+    </Message>
+  );
+}
+
+export interface ErrorPopupProps {
+  message?: string;
+  open: boolean;
+  onDismiss: () => void;
+}
+
+/**
+ * Shows a dismissable error message in the bottom left corner of the screen.
+ */
+export function ErrorPopup(props: ErrorPopupProps) {
+  return (
+    <Portal open={props.open} onClose={props.onDismiss}>
+      <Message negative className="errorPopup" onDismiss={props.onDismiss}>
+        <Message.Header>
+          <FormattedMessage id="error.error" defaultMessage={'Error'} />
+        </Message.Header>
+        <p>{props.message}</p>
+      </Message>
+    </Portal>
+  );
+}