diff --git a/js/app.js b/js/app.js
index 4ce668d4..2c1164a2 100644
--- a/js/app.js
+++ b/js/app.js
@@ -27,6 +27,7 @@ import { attachHealthBadges } from "./gridHealth.js";
 import { attachUrlHealthBadges } from "./urlHealthObserver.js";
 import { updateVideoCardSourceVisibility } from "./utils/cardSourceVisibility.js";
 import { collectVideoTags } from "./utils/videoTags.js";
+import { normalizeHashtag } from "./utils/hashtagNormalization.js";
 import { sanitizeProfileMediaUrl } from "./utils/profileMedia.js";
 import { ADMIN_INITIAL_EVENT_BLACKLIST } from "./lists.js";
 import { userBlocks } from "./userBlocks.js";
@@ -2514,16 +2515,7 @@ class Application {
   }
 
   normalizeTagPreferenceCandidate(tag) {
-    if (typeof tag !== "string") {
-      return "";
-    }
-
-    const trimmed = tag.trim().replace(/^#+/, "");
-    if (!trimmed) {
-      return "";
-    }
-
-    return trimmed.toLowerCase();
+    return normalizeHashtag(tag);
   }
 
   getTagPreferenceState(tag) {
diff --git a/js/feedEngine/index.js b/js/feedEngine/index.js
index 67adf59a..4f03bd02 100644
--- a/js/feedEngine/index.js
+++ b/js/feedEngine/index.js
@@ -8,6 +8,7 @@ export {
 export {
   createDedupeByRootStage,
   createBlacklistFilterStage,
+  createTagPreferenceFilterStage,
   createWatchHistorySuppressionStage,
   createModerationStage,
   createResolvePostedAtStage,
diff --git a/js/feedEngine/stages.js b/js/feedEngine/stages.js
index 38c56beb..a4b583c3 100644
--- a/js/feedEngine/stages.js
+++ b/js/feedEngine/stages.js
@@ -10,10 +10,25 @@ import nostrService from "../services/nostrService.js";
 import moderationService from "../services/moderationService.js";
 import logger from "../utils/logger.js";
 import { dedupeToNewestByRoot } from "../utils/videoDeduper.js";
+import { normalizeHashtag } from "../utils/hashtagNormalization.js";
 import { isPlainObject, toSet, hasDisinterestedTag } from "./utils.js";
 
 const FEED_HIDE_BYPASS_NAMES = new Set(["home", "recent"]);
 
+function normalizeTagSet(values) {
+  const normalized = new Set();
+  const source = toSet(values);
+
+  for (const value of source) {
+    const tag = normalizeHashtag(value);
+    if (tag) {
+      normalized.add(tag);
+    }
+  }
+
+  return normalized;
+}
+
 function resolveDedupeFunction(customDedupe) {
   if (typeof customDedupe === "function") {
     return customDedupe;
@@ -258,6 +273,43 @@ export function createResolvePostedAtStage({
   };
 }
 
+export function createTagPreferenceFilterStage({
+  stageName = "tag-preference-filter",
+} = {}) {
+  return async function tagPreferenceFilterStage(items = [], context = {}) {
+    const tagPreferences = context?.runtime?.tagPreferences;
+    const disinterests = normalizeTagSet(tagPreferences?.disinterests);
+    if (!disinterests.size) {
+      return items;
+    }
+
+    const results = [];
+
+    for (const item of items) {
+      const video = item?.video;
+      if (!video || typeof video !== "object") {
+        results.push(item);
+        continue;
+      }
+
+      if (hasDisinterestedTag(video, disinterests)) {
+        context?.addWhy?.({
+          stage: stageName,
+          type: "filter",
+          reason: "disinterested-tag",
+          videoId: typeof video.id === "string" ? video.id : null,
+          pubkey: typeof video.pubkey === "string" ? video.pubkey : null,
+        });
+        continue;
+      }
+
+      results.push(item);
+    }
+
+    return results;
+  };
+}
+
 export function createBlacklistFilterStage({
   stageName = "blacklist-filter",
   shouldIncludeVideo,
@@ -277,7 +329,7 @@ export function createBlacklistFilterStage({
     const options = { blacklistedEventIds: blacklist, isAuthorBlocked };
 
     const tagPreferences = context?.runtime?.tagPreferences;
-    const disinterests = toSet(tagPreferences?.disinterests);
+    const disinterests = normalizeTagSet(tagPreferences?.disinterests);
     const hasTagPreferences = disinterests.size > 0;
 
     const results = [];
diff --git a/js/feedEngine/utils.js b/js/feedEngine/utils.js
index 44b94112..915c950b 100644
--- a/js/feedEngine/utils.js
+++ b/js/feedEngine/utils.js
@@ -1,5 +1,7 @@
 // js/feedEngine/utils.js
 
+import { normalizeHashtag } from "../utils/hashtagNormalization.js";
+
 export function isPlainObject(value) {
   if (value === null || typeof value !== "object") {
     return false;
@@ -33,11 +35,16 @@ export function hasDisinterestedTag(video, disinterestsSet) {
     return false;
   }
 
+  const matchesDisinterest = (tag) => {
+    const normalized = normalizeHashtag(tag);
+    return Boolean(normalized && disinterestsSet.has(normalized));
+  };
+
   // Check raw tags
   if (Array.isArray(video.tags)) {
     for (const tag of video.tags) {
       if (Array.isArray(tag) && tag[0] === "t" && typeof tag[1] === "string") {
-        if (disinterestsSet.has(tag[1].toLowerCase())) {
+        if (matchesDisinterest(tag[1])) {
           return true;
         }
       }
@@ -47,7 +54,7 @@ export function hasDisinterestedTag(video, disinterestsSet) {
   // Check NIP-71 metadata hashtags if available
   if (video.nip71 && Array.isArray(video.nip71.hashtags)) {
     for (const tag of video.nip71.hashtags) {
-      if (typeof tag === "string" && disinterestsSet.has(tag.toLowerCase())) {
+      if (typeof tag === "string" && matchesDisinterest(tag)) {
         return true;
       }
     }
diff --git a/js/services/hashtagPreferencesService.js b/js/services/hashtagPreferencesService.js
index 86c6a1bb..b4788b5b 100644
--- a/js/services/hashtagPreferencesService.js
+++ b/js/services/hashtagPreferencesService.js
@@ -15,6 +15,7 @@ import {
   assertAnyRelayAccepted,
 } from "../nostrPublish.js";
 import { userLogger, devLogger } from "../utils/logger.js";
+import { normalizeHashtag } from "../utils/hashtagNormalization.js";
 import { profileCache } from "../state/profileCache.js";
 
 const LOG_PREFIX = "[HashtagPreferences]";
@@ -95,19 +96,6 @@ function sanitizeRelayList(candidate) {
     : [];
 }
 
-function normalizeTag(input) {
-  if (typeof input !== "string") {
-    return "";
-  }
-
-  const trimmed = input.trim().replace(/^#+/, "");
-  if (!trimmed) {
-    return "";
-  }
-
-  return trimmed.toLowerCase();
-}
-
 function normalizeEncryptionToken(value) {
   if (typeof value !== "string") {
     return "";
@@ -133,7 +121,7 @@ function normalizePreferencesPayload(payload) {
 
   const interests = new Set();
   for (const tag of rawInterests) {
-    const normalizedTag = normalizeTag(tag);
+    const normalizedTag = normalizeHashtag(tag);
     if (normalizedTag) {
       interests.add(normalizedTag);
     }
@@ -141,7 +129,7 @@ function normalizePreferencesPayload(payload) {
 
   const disinterests = new Set();
   for (const tag of rawDisinterests) {
-    const normalizedTag = normalizeTag(tag);
+    const normalizedTag = normalizeHashtag(tag);
     if (!normalizedTag) {
       continue;
     }
@@ -342,7 +330,7 @@ class HashtagPreferencesService {
   }
 
   addInterest(tag) {
-    const normalized = normalizeTag(tag);
+    const normalized = normalizeHashtag(tag);
     if (!normalized) {
       return false;
     }
@@ -360,7 +348,7 @@ class HashtagPreferencesService {
   }
 
   removeInterest(tag) {
-    const normalized = normalizeTag(tag);
+    const normalized = normalizeHashtag(tag);
     if (!normalized || !this.interests.has(normalized)) {
       return false;
     }
@@ -371,7 +359,7 @@ class HashtagPreferencesService {
   }
 
   addDisinterest(tag) {
-    const normalized = normalizeTag(tag);
+    const normalized = normalizeHashtag(tag);
     if (!normalized) {
       return false;
     }
@@ -389,7 +377,7 @@ class HashtagPreferencesService {
   }
 
   removeDisinterest(tag) {
-    const normalized = normalizeTag(tag);
+    const normalized = normalizeHashtag(tag);
     if (!normalized || !this.disinterests.has(normalized)) {
       return false;
     }
diff --git a/js/ui/components/VideoModal.js b/js/ui/components/VideoModal.js
index fee035dc..f34761e4 100644
--- a/js/ui/components/VideoModal.js
+++ b/js/ui/components/VideoModal.js
@@ -35,6 +35,7 @@ import {
   formatShortNpub as defaultFormatShortNpub,
 } from "../../utils/formatters.js";
 import { sanitizeProfileMediaUrl } from "../../utils/profileMedia.js";
+import { normalizeHashtag } from "../../utils/hashtagNormalization.js";
 import { getBreakpointLg } from "../../designSystem/metrics.js";
 
 const HEX64_REGEX = /^[0-9a-f]{64}$/i;
@@ -2917,7 +2918,7 @@ export class VideoModal {
       }
 
       const raw = typeof entry === "string" ? entry : String(entry ?? "");
-      const trimmed = raw.trim().replace(/^#+/, "");
+      const trimmed = normalizeHashtag(raw);
 
       if (!trimmed) {
         continue;
diff --git a/js/ui/components/nip71FormManager.js b/js/ui/components/nip71FormManager.js
index 6c7dc589..7c970cf9 100644
--- a/js/ui/components/nip71FormManager.js
+++ b/js/ui/components/nip71FormManager.js
@@ -1,4 +1,8 @@
 import { userLogger } from "../../utils/logger.js";
+import {
+  normalizeHashtag,
+  formatHashtag,
+} from "../../utils/hashtagNormalization.js";
 // NOTE: Keep the Upload, Edit, and Revert modals in lockstep when updating NIP-71 form features.
 
 const REPEATER_KEYS = ["imeta", "text-track", "segment", "t", "p", "r"];
@@ -468,22 +472,11 @@ export class Nip71FormManager {
       value = `${value ?? ""}`;
     }
 
-    const trimmed = value.trim();
-    if (!trimmed) {
-      return "";
-    }
-
-    const withoutHash = trimmed.replace(/^#+/, "").trim();
-    if (!withoutHash) {
-      return "";
-    }
-
-    return withoutHash.toLowerCase();
+    return normalizeHashtag(value);
   }
 
   renderHashtagValue(value) {
-    const sanitized = this.sanitizeHashtagValue(value);
-    return sanitized ? `#${sanitized}` : "";
+    return formatHashtag(value);
   }
 
   collectNestedValues(entry, nestedKey) {
@@ -804,4 +797,3 @@ export class Nip71FormManager {
     return this.sections.get(key) || null;
   }
 }
-
diff --git a/js/ui/components/tagPreferenceMenu.js b/js/ui/components/tagPreferenceMenu.js
index b56a3bbb..fa25b148 100644
--- a/js/ui/components/tagPreferenceMenu.js
+++ b/js/ui/components/tagPreferenceMenu.js
@@ -1,4 +1,8 @@
 import { normalizeDesignSystemContext } from "../../designSystem.js";
+import {
+  normalizeHashtag,
+  formatHashtag,
+} from "../../utils/hashtagNormalization.js";
 
 export const TAG_PREFERENCE_ACTIONS = {
   ADD_INTEREST: "add-interest",
@@ -83,19 +87,9 @@ function appendMenuAction(doc, list, { text, action, dataset = {}, disabled = fa
 }
 
 function normalizeTag(tag) {
-  if (typeof tag !== "string") {
-    return { label: "", normalized: "" };
-  }
-
-  const trimmed = tag.trim();
-  if (!trimmed) {
-    return { label: "", normalized: "" };
-  }
-
-  const withoutHash = trimmed.replace(/^#+/, "");
-  const normalized = withoutHash.toLowerCase();
+  const normalized = normalizeHashtag(tag);
   return {
-    label: withoutHash,
+    label: normalized,
     normalized,
   };
 }
@@ -172,7 +166,7 @@ export function createTagPreferenceMenu({
   normalizeDesignSystemContext(designSystem);
 
   const { label, normalized } = normalizeTag(tag);
-  const headingLabel = label ? `#${label}` : "Tag preferences";
+  const headingLabel = label ? formatHashtag(label) : "Tag preferences";
 
   const { panel, list } = ensureMenuContainer(doc, ["w-56", "p-0"]);
   panel.dataset.menu = "tag-preference";
@@ -191,7 +185,7 @@ export function createTagPreferenceMenu({
   }
 
   const buttons = {};
-  const actionDataset = { tag: label || normalized };
+  const actionDataset = { tag: normalized };
 
   buttons.addInterest = appendMenuAction(doc, list, {
     text: "Add to interests",
@@ -225,7 +219,7 @@ export function createTagPreferenceMenu({
     }
     try {
       onAction(action, {
-        tag: label || normalized,
+        tag: normalized,
         normalizedTag: normalized,
         event,
         button,
diff --git a/js/ui/profileModalController.js b/js/ui/profileModalController.js
index c3670352..a1c74187 100644
--- a/js/ui/profileModalController.js
+++ b/js/ui/profileModalController.js
@@ -16,6 +16,10 @@ import {
 import { getBreakpointLg } from "../designSystem/metrics.js";
 import { getProviderMetadata } from "../services/authProviders/index.js";
 import { devLogger, userLogger } from "../utils/logger.js";
+import {
+  normalizeHashtag,
+  formatHashtag,
+} from "../utils/hashtagNormalization.js";
 import { getActiveSigner } from "../nostr/client.js";
 
 const noop = () => {};
@@ -4465,24 +4469,11 @@ export class ProfileModalController {
   }
 
   normalizeHashtagTag(value) {
-    if (typeof value !== "string") {
-      return "";
-    }
-
-    const trimmed = value.trim();
-    if (!trimmed) {
-      return "";
-    }
-
-    return trimmed.replace(/^#+/, "").toLowerCase();
+    return normalizeHashtag(value);
   }
 
   formatHashtagTag(value) {
-    const normalized = this.normalizeHashtagTag(value);
-    if (!normalized) {
-      return "";
-    }
-    return `#${normalized}`;
+    return formatHashtag(value);
   }
 
   sanitizeHashtagList(list) {
diff --git a/js/utils/hashtagNormalization.js b/js/utils/hashtagNormalization.js
new file mode 100644
index 00000000..c1d0f624
--- /dev/null
+++ b/js/utils/hashtagNormalization.js
@@ -0,0 +1,50 @@
+// js/utils/hashtagNormalization.js
+
+const HASH_PREFIX_PATTERN = /^#+/;
+
+/**
+ * Normalize hashtags consistently across storage, matching, and UI validation.
+ *
+ * Normalization rules:
+ * 1) Trim surrounding whitespace.
+ * 2) Strip leading "#" characters.
+ * 3) Lowercase the remaining value.
+ *
+ * Note: We do not strip punctuation today. Only add punctuation stripping if
+ * product explicitly decides to change the rules.
+ *
+ * @param {string} value
+ * @returns {string} normalized hashtag or empty string when invalid.
+ */
+export function normalizeHashtag(value) {
+  if (typeof value !== "string") {
+    return "";
+  }
+
+  const trimmed = value.trim();
+  if (!trimmed) {
+    return "";
+  }
+
+  const withoutHashes = trimmed.replace(HASH_PREFIX_PATTERN, "").trim();
+  if (!withoutHashes) {
+    return "";
+  }
+
+  return withoutHashes.toLowerCase();
+}
+
+/**
+ * Format a hashtag for display, ensuring a single leading hash.
+ *
+ * @param {string} value
+ * @returns {string}
+ */
+export function formatHashtag(value) {
+  const normalized = normalizeHashtag(value);
+  if (!normalized) {
+    return "";
+  }
+
+  return `#${normalized}`;
+}