diff --git a/viewer/src/api.ts b/viewer/src/api.ts
index 72dc618..ee049ed 100644
--- a/viewer/src/api.ts
+++ b/viewer/src/api.ts
@@ -1,15 +1,19 @@
 import type { EventsResponse, ExclusionsMap, QuestData } from "./types";
 
-const DATA_URL = import.meta.env.VITE_DATA_URL as string;
+function getDataUrl(): string {
+  const url = import.meta.env.VITE_DATA_URL;
+  if (!url) throw new Error("VITE_DATA_URL is not set");
+  return url;
+}
 
 export async function fetchEvents(signal?: AbortSignal): Promise<EventsResponse> {
-  const res = await fetch(`${DATA_URL}/events.json`, { signal });
+  const res = await fetch(`${getDataUrl()}/events.json`, { signal });
   if (!res.ok) throw new Error(`Failed to fetch events: ${res.status}`);
   return res.json();
 }
 
 export async function fetchExclusions(signal?: AbortSignal): Promise<ExclusionsMap> {
-  const res = await fetch(`${DATA_URL}/exclusions.json`, { signal });
+  const res = await fetch(`${getDataUrl()}/exclusions.json`, { signal });
   if (!res.ok) return {};
   return res.json();
 }
@@ -19,7 +23,7 @@ export async function fetchQuestData(
   questId: string,
   signal?: AbortSignal,
 ): Promise<QuestData | null> {
-  const res = await fetch(`${DATA_URL}/${eventId}/${questId}.json`, { signal });
+  const res = await fetch(`${getDataUrl()}/${eventId}/${questId}.json`, { signal });
   // S3 + CloudFront では未作成のオブジェクトに対して 403 が返るため、
   // 404 と同様に「データ未登録」として扱い、エラーではなく null を返す
   if (res.status === 403 || res.status === 404) return null;
diff --git a/viewer/src/components/ReportTable.tsx b/viewer/src/components/ReportTable.tsx
index 2f2e559..9ff799e 100644
--- a/viewer/src/components/ReportTable.tsx
+++ b/viewer/src/components/ReportTable.tsx
@@ -3,7 +3,7 @@ import { createExcludedIdSet, isOutlier } from "../aggregate";
 import { formatItemHeader, formatNote, formatTimestamp } from "../formatters";
 import { useSortState } from "../hooks/useSortState";
 import type { SortKey } from "../reportTableUtils";
-import { sortReports } from "../reportTableUtils";
+import { getReporterName, sortReports } from "../reportTableUtils";
 import type { Exclusion, ItemOutlierStats, ItemStats, Report } from "../types";
 import {
   sortIndicator,
@@ -80,13 +80,13 @@ export function ReportTable({ reports, exclusions, itemNames, outlierStats, stat
             return (
               <tr key={r.id} style={rowStyle} title={excluded ? exclusionMap.get(r.id) : undefined}>
                 <td style={tdStyle}>{excluded ? "除外" : "有効"}</td>
-                <td style={tdStyleReporter} title={r.reporterName || r.reporter || "匿名"}>
+                <td style={tdStyleReporter} title={getReporterName(r)}>
                   <a
                     href={`https://fgodrop.max747.org/reports/${r.id}`}
                     target="_blank"
                     rel="noopener noreferrer"
                   >
-                    {r.reporterName || r.reporter || "匿名"}
+                    {getReporterName(r)}
                   </a>
                 </td>
                 <td style={tdStyleRight}>{r.runcount}</td>
diff --git a/viewer/src/reporterSummaryUtils.ts b/viewer/src/reporterSummaryUtils.ts
index 0dac7c6..0493372 100644
--- a/viewer/src/reporterSummaryUtils.ts
+++ b/viewer/src/reporterSummaryUtils.ts
@@ -1,3 +1,4 @@
+import { getReporterName } from "./reportTableUtils";
 import type { ExclusionsMap, QuestData, SortDir } from "./types";
 
 export interface ReportDetail {
@@ -33,7 +34,7 @@ export function aggregateReporters(
     for (const r of qd.reports) {
       if (excludedIds.has(r.id)) continue;
 
-      const name = r.reporterName || r.reporter || "匿名";
+      const name = getReporterName(r);
       const entry = map.get(name) ?? {
         reporter: name,
         xId: r.reporter || "",