diff --git a/js/app.js b/js/app.js
index e0a7a818..07c936f4 100644
--- a/js/app.js
+++ b/js/app.js
@@ -5811,6 +5811,10 @@ class Application {
   }
 
   buildExploreFeedRuntime() {
+    const exploreDataService =
+      this.exploreDataService && typeof this.exploreDataService === "object"
+        ? this.exploreDataService
+        : null;
     const blacklist =
       this.blacklistedEventIds instanceof Set
         ? new Set(this.blacklistedEventIds)
@@ -5828,18 +5832,26 @@ class Application {
     const { interests = [], disinterests = [] } = preferenceSource || {};
     const moderationThresholds = this.getActiveModerationThresholds();
 
+    const watchHistorySource =
+      exploreDataService && typeof exploreDataService.getWatchHistoryTagCounts === "function"
+        ? exploreDataService.getWatchHistoryTagCounts()
+        : this.watchHistoryTagCounts;
     const watchHistoryTagCounts =
-      this.watchHistoryTagCounts instanceof Map
-        ? new Map(this.watchHistoryTagCounts)
-        : this.watchHistoryTagCounts &&
-          typeof this.watchHistoryTagCounts === "object"
-        ? { ...this.watchHistoryTagCounts }
+      watchHistorySource instanceof Map
+        ? new Map(watchHistorySource)
+        : watchHistorySource && typeof watchHistorySource === "object"
+        ? { ...watchHistorySource }
         : undefined;
+
+    const exploreTagSource =
+      exploreDataService && typeof exploreDataService.getTagIdf === "function"
+        ? exploreDataService.getTagIdf()
+        : this.exploreTagIdf;
     const exploreTagIdf =
-      this.exploreTagIdf instanceof Map
-        ? new Map(this.exploreTagIdf)
-        : this.exploreTagIdf && typeof this.exploreTagIdf === "object"
-        ? { ...this.exploreTagIdf }
+      exploreTagSource instanceof Map
+        ? new Map(exploreTagSource)
+        : exploreTagSource && typeof exploreTagSource === "object"
+        ? { ...exploreTagSource }
         : undefined;
 
     return {
@@ -9955,6 +9967,18 @@ class Application {
       this.watchHistoryTelemetry = null;
     }
 
+    if (this.exploreDataService && typeof this.exploreDataService.destroy === "function") {
+      try {
+        this.exploreDataService.destroy();
+      } catch (error) {
+        devLogger.warn(
+          "[Application] Failed to destroy explore data service:",
+          error,
+        );
+      }
+      this.exploreDataService = null;
+    }
+
     if (typeof this.unsubscribeFromHashtagPreferencesChange === "function") {
       try {
         this.unsubscribeFromHashtagPreferencesChange();
diff --git a/js/services/exploreDataService.js b/js/services/exploreDataService.js
new file mode 100644
index 00000000..67a69297
--- /dev/null
+++ b/js/services/exploreDataService.js
@@ -0,0 +1,371 @@
+import { devLogger } from "../utils/logger.js";
+import { normalizeHashtag } from "../utils/hashtagNormalization.js";
+import { normalizePointerInput } from "../nostr/watchHistory.js";
+import { buildVideoAddressPointer } from "../utils/videoPointer.js";
+
+const DEFAULT_IDF_REFRESH_INTERVAL_MS = 5 * 60 * 1000;
+const DEFAULT_HISTORY_REFRESH_INTERVAL_MS = 60 * 1000;
+const DEFAULT_REFRESH_DEBOUNCE_MS = 200;
+
+function normalizeAddressKey(value) {
+  if (typeof value !== "string") {
+    return "";
+  }
+  const trimmed = value.trim();
+  if (!trimmed) {
+    return "";
+  }
+  return trimmed.toLowerCase();
+}
+
+function collectVideoTags(video) {
+  const tags = new Set();
+
+  if (!video || typeof video !== "object") {
+    return tags;
+  }
+
+  if (Array.isArray(video.tags)) {
+    for (const tag of video.tags) {
+      if (Array.isArray(tag) && tag[0] === "t" && typeof tag[1] === "string") {
+        const normalized = normalizeHashtag(tag[1]);
+        if (normalized) {
+          tags.add(normalized);
+        }
+      }
+    }
+  }
+
+  if (Array.isArray(video.nip71?.hashtags)) {
+    for (const tag of video.nip71.hashtags) {
+      if (typeof tag !== "string") {
+        continue;
+      }
+      const normalized = normalizeHashtag(tag);
+      if (normalized) {
+        tags.add(normalized);
+      }
+    }
+  }
+
+  return tags;
+}
+
+export async function buildWatchHistoryTagCounts({
+  watchHistoryService,
+  nostrService,
+  actor,
+} = {}) {
+  if (!watchHistoryService || typeof watchHistoryService.loadLatest !== "function") {
+    return new Map();
+  }
+
+  let items = [];
+  try {
+    items = await Promise.resolve(
+      watchHistoryService.loadLatest(actor, { allowStale: true })
+    );
+  } catch (error) {
+    devLogger.warn("[exploreData] Failed to load watch history entries:", error);
+    items = [];
+  }
+
+  const videosMap =
+    nostrService && typeof nostrService.getVideosMap === "function"
+      ? nostrService.getVideosMap()
+      : new Map();
+
+  const needsAddressIndex = Array.isArray(items)
+    ? items.some((item) => {
+        const pointer = normalizePointerInput(item?.pointer || item);
+        return pointer?.type === "a";
+      })
+    : false;
+
+  let addressIndex = null;
+  if (needsAddressIndex) {
+    addressIndex = new Map();
+    for (const video of videosMap.values()) {
+      const address = buildVideoAddressPointer(video);
+      const key = normalizeAddressKey(address);
+      if (key) {
+        addressIndex.set(key, video);
+      }
+    }
+  }
+
+  const counts = new Map();
+  if (!Array.isArray(items)) {
+    return counts;
+  }
+
+  for (const entry of items) {
+    const pointer = normalizePointerInput(entry?.pointer || entry);
+    let video = entry?.video || entry?.metadata?.video || null;
+
+    if (pointer?.type === "e" && pointer.value) {
+      const eventId = typeof pointer.value === "string" ? pointer.value.trim() : "";
+      if (eventId) {
+        video = videosMap.get(eventId) || videosMap.get(eventId.toLowerCase()) || video;
+      }
+    } else if (pointer?.type === "a" && pointer.value && addressIndex) {
+      const key = normalizeAddressKey(pointer.value);
+      if (key && addressIndex.has(key)) {
+        video = addressIndex.get(key);
+      }
+    }
+
+    if (!video) {
+      continue;
+    }
+
+    const tags = collectVideoTags(video);
+    for (const tag of tags) {
+      counts.set(tag, (counts.get(tag) || 0) + 1);
+    }
+  }
+
+  return counts;
+}
+
+export function buildTagIdf({ videos } = {}) {
+  const idf = new Map();
+  const list = Array.isArray(videos) ? videos : [];
+  if (!list.length) {
+    return idf;
+  }
+
+  const docFrequency = new Map();
+  const totalDocs = list.length;
+
+  for (const video of list) {
+    const tags = collectVideoTags(video);
+    if (!tags.size) {
+      continue;
+    }
+
+    for (const tag of tags) {
+      docFrequency.set(tag, (docFrequency.get(tag) || 0) + 1);
+    }
+  }
+
+  for (const [tag, df] of docFrequency.entries()) {
+    const ratio = (totalDocs + 1) / (df + 1);
+    const value = 1 + Math.log(ratio);
+    if (Number.isFinite(value) && value > 0) {
+      idf.set(tag, value);
+    }
+  }
+
+  return idf;
+}
+
+export default class ExploreDataService {
+  constructor({
+    watchHistoryService,
+    nostrService,
+    getActiveActor,
+    logger = devLogger,
+    idfRefreshIntervalMs = DEFAULT_IDF_REFRESH_INTERVAL_MS,
+    historyRefreshIntervalMs = DEFAULT_HISTORY_REFRESH_INTERVAL_MS,
+    refreshDebounceMs = DEFAULT_REFRESH_DEBOUNCE_MS,
+  } = {}) {
+    this.watchHistoryService = watchHistoryService;
+    this.nostrService = nostrService;
+    this.getActiveActor =
+      typeof getActiveActor === "function" ? getActiveActor : () => "";
+    this.logger = logger && typeof logger.warn === "function" ? logger : devLogger;
+    this.idfRefreshIntervalMs = idfRefreshIntervalMs;
+    this.historyRefreshIntervalMs = historyRefreshIntervalMs;
+    this.refreshDebounceMs = refreshDebounceMs;
+
+    this.watchHistoryTagCounts = new Map();
+    this.watchHistoryTagCountsUpdatedAt = 0;
+    this.tagIdf = new Map();
+    this.tagIdfUpdatedAt = 0;
+
+    this.watchHistoryRefreshHandle = null;
+    this.tagIdfRefreshHandle = null;
+    this.watchHistoryInterval = null;
+    this.tagIdfInterval = null;
+    this.unsubscribeHandlers = [];
+  }
+
+  initialize() {
+    this.refreshWatchHistoryTagCounts({ force: true, reason: "init" });
+    this.refreshTagIdf({ force: true, reason: "init" });
+    this.subscribeToUpdates();
+    this.startIntervals();
+  }
+
+  startIntervals() {
+    this.clearIntervals();
+    if (Number.isFinite(this.historyRefreshIntervalMs) && this.historyRefreshIntervalMs > 0) {
+      this.watchHistoryInterval = setInterval(() => {
+        this.refreshWatchHistoryTagCounts({ reason: "interval" });
+      }, this.historyRefreshIntervalMs);
+    }
+    if (Number.isFinite(this.idfRefreshIntervalMs) && this.idfRefreshIntervalMs > 0) {
+      this.tagIdfInterval = setInterval(() => {
+        this.refreshTagIdf({ reason: "interval" });
+      }, this.idfRefreshIntervalMs);
+    }
+  }
+
+  clearIntervals() {
+    if (this.watchHistoryInterval) {
+      clearInterval(this.watchHistoryInterval);
+      this.watchHistoryInterval = null;
+    }
+    if (this.tagIdfInterval) {
+      clearInterval(this.tagIdfInterval);
+      this.tagIdfInterval = null;
+    }
+  }
+
+  subscribeToUpdates() {
+    this.unsubscribeHandlers.forEach((unsubscribe) => {
+      if (typeof unsubscribe === "function") {
+        unsubscribe();
+      }
+    });
+    this.unsubscribeHandlers = [];
+
+    if (this.watchHistoryService && typeof this.watchHistoryService.subscribe === "function") {
+      const unsubscribe = this.watchHistoryService.subscribe("fingerprint", () => {
+        this.queueWatchHistoryRefresh("watch-history");
+      });
+      this.unsubscribeHandlers.push(unsubscribe);
+    }
+
+    if (this.nostrService && typeof this.nostrService.on === "function") {
+      const events = [
+        "videos:updated",
+        "videos:fetched",
+        "videos:published",
+        "videos:edited",
+        "videos:deleted",
+        "videos:cache",
+      ];
+      events.forEach((eventName) => {
+        const unsubscribe = this.nostrService.on(eventName, () => {
+          this.queueTagIdfRefresh(eventName);
+        });
+        this.unsubscribeHandlers.push(unsubscribe);
+      });
+    }
+  }
+
+  queueWatchHistoryRefresh(reason) {
+    if (this.watchHistoryRefreshHandle) {
+      return;
+    }
+    this.watchHistoryRefreshHandle = setTimeout(() => {
+      this.watchHistoryRefreshHandle = null;
+      this.refreshWatchHistoryTagCounts({ reason });
+    }, this.refreshDebounceMs);
+  }
+
+  queueTagIdfRefresh(reason) {
+    if (this.tagIdfRefreshHandle) {
+      return;
+    }
+    this.tagIdfRefreshHandle = setTimeout(() => {
+      this.tagIdfRefreshHandle = null;
+      this.refreshTagIdf({ reason });
+    }, this.refreshDebounceMs);
+  }
+
+  async refreshWatchHistoryTagCounts({ force = false, reason } = {}) {
+    const now = Date.now();
+    if (!force && this.watchHistoryTagCountsUpdatedAt) {
+      const elapsed = now - this.watchHistoryTagCountsUpdatedAt;
+      if (elapsed < this.historyRefreshIntervalMs) {
+        return this.watchHistoryTagCounts;
+      }
+    }
+
+    try {
+      const actorRaw = this.getActiveActor();
+      const actor = typeof actorRaw === "string" && actorRaw.trim() ? actorRaw.trim() : undefined;
+      const counts = await buildWatchHistoryTagCounts({
+        watchHistoryService: this.watchHistoryService,
+        nostrService: this.nostrService,
+        actor,
+      });
+      this.watchHistoryTagCounts = counts instanceof Map ? counts : new Map();
+      this.watchHistoryTagCountsUpdatedAt = now;
+      return this.watchHistoryTagCounts;
+    } catch (error) {
+      if (this.logger?.warn) {
+        this.logger.warn(
+          "[exploreData] Failed to refresh watch history tag counts:",
+          error,
+        );
+      }
+      if (reason) {
+        return this.watchHistoryTagCounts;
+      }
+      return this.watchHistoryTagCounts;
+    }
+  }
+
+  refreshTagIdf({ force = false, videos, reason } = {}) {
+    const now = Date.now();
+    if (!force && this.tagIdfUpdatedAt) {
+      const elapsed = now - this.tagIdfUpdatedAt;
+      if (elapsed < this.idfRefreshIntervalMs) {
+        return this.tagIdf;
+      }
+    }
+
+    const sourceVideos = Array.isArray(videos)
+      ? videos
+      : this.nostrService && typeof this.nostrService.getFilteredActiveVideos === "function"
+      ? this.nostrService.getFilteredActiveVideos()
+      : [];
+
+    try {
+      this.tagIdf = buildTagIdf({ videos: sourceVideos });
+      this.tagIdfUpdatedAt = now;
+    } catch (error) {
+      if (this.logger?.warn) {
+        this.logger.warn("[exploreData] Failed to refresh tag IDF:", error);
+      }
+    }
+
+    if (reason) {
+      return this.tagIdf;
+    }
+
+    return this.tagIdf;
+  }
+
+  getWatchHistoryTagCounts() {
+    return this.watchHistoryTagCounts;
+  }
+
+  getTagIdf() {
+    return this.tagIdf;
+  }
+
+  destroy() {
+    this.clearIntervals();
+
+    if (this.watchHistoryRefreshHandle) {
+      clearTimeout(this.watchHistoryRefreshHandle);
+      this.watchHistoryRefreshHandle = null;
+    }
+    if (this.tagIdfRefreshHandle) {
+      clearTimeout(this.tagIdfRefreshHandle);
+      this.tagIdfRefreshHandle = null;
+    }
+
+    this.unsubscribeHandlers.forEach((unsubscribe) => {
+      if (typeof unsubscribe === "function") {
+        unsubscribe();
+      }
+    });
+    this.unsubscribeHandlers = [];
+  }
+}
diff --git a/js/ui/applicationBootstrap.js b/js/ui/applicationBootstrap.js
index 064fa2f9..1538f551 100644
--- a/js/ui/applicationBootstrap.js
+++ b/js/ui/applicationBootstrap.js
@@ -9,6 +9,7 @@ import PlaybackService from "../services/playbackService.js";
 import AuthService from "../services/authService.js";
 import DiscussionCountService from "../services/discussionCountService.js";
 import CommentThreadService from "../services/commentThreadService.js";
+import ExploreDataService from "../services/exploreDataService.js";
 import hashtagPreferences, {
   HASHTAG_PREFERENCES_EVENTS,
 } from "../services/hashtagPreferencesService.js";
@@ -133,6 +134,7 @@ export default class ApplicationBootstrap {
     app.relayManager = relayManager;
     app.activeIntervals = [];
     app.watchHistoryTelemetry = null;
+    app.exploreDataService = null;
     app.authEventUnsubscribes = [];
     app.unsubscribeFromNostrService = null;
     app.designSystemContext = {
@@ -291,6 +293,19 @@ export default class ApplicationBootstrap {
       onViewLogged: (detail) => app.handleFeedViewTelemetry(detail),
     });
 
+    app.exploreDataService =
+      this.services.exploreDataService ||
+      new ExploreDataService({
+        watchHistoryService,
+        nostrService: app.nostrService,
+        getActiveActor: () =>
+          typeof app.pubkey === "string" && app.pubkey ? app.pubkey : "",
+        logger: devLogger,
+      });
+    if (app.exploreDataService && typeof app.exploreDataService.initialize === "function") {
+      app.exploreDataService.initialize();
+    }
+
     const playbackDependencies = {
       torrentClient: this.services.torrentClient || torrentClient,
       deriveTorrentPlaybackConfig: