diff --git a/js/app.js b/js/app.js
index 60b89dfb..63c18f5e 100644
--- a/js/app.js
+++ b/js/app.js
@@ -1879,6 +1879,9 @@ class Application {
       if (candidate.isPrivate === true) {
         continue;
       }
+      if (candidate.isNsfw === true && ALLOW_NSFW_CONTENT !== true) {
+        continue;
+      }
 
       const candidatePubkey = typeof candidate.pubkey === "string" ? candidate.pubkey : "";
       if (candidatePubkey && this.isAuthorBlocked(candidatePubkey)) {
diff --git a/tests/app/similar-content.test.mjs b/tests/app/similar-content.test.mjs
new file mode 100644
index 00000000..0f0858f2
--- /dev/null
+++ b/tests/app/similar-content.test.mjs
@@ -0,0 +1,200 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+
+import Application from "../../js/app.js";
+
+const computeSimilarContent = Application.prototype.computeSimilarContentCandidates;
+
+function createAppStub({ videos = [] } = {}) {
+  const videosMap = new Map();
+  for (const video of videos) {
+    if (video && typeof video.id === "string") {
+      videosMap.set(video.id, video);
+    }
+  }
+
+  return {
+    videoListView: { currentVideos: videos },
+    videosMap,
+    getKnownVideoPostedAt(video) {
+      if (Number.isFinite(video?.rootCreatedAt)) {
+        return Math.floor(video.rootCreatedAt);
+      }
+      if (Number.isFinite(video?.created_at)) {
+        return Math.floor(video.created_at);
+      }
+      return null;
+    },
+    buildShareUrlFromEventId(id) {
+      return id ? `https://bitvid.invalid/${id}` : "";
+    },
+    formatTimeAgo(timestamp) {
+      return Number.isFinite(timestamp) ? `${timestamp}s` : "";
+    },
+    deriveVideoPointerInfo(video) {
+      if (video?.pointerInfo) {
+        return video.pointerInfo;
+      }
+      if (typeof video?.pointerKey === "string" && video.pointerKey.trim()) {
+        return { key: video.pointerKey.trim() };
+      }
+      return null;
+    },
+    isAuthorBlocked() {
+      return false;
+    },
+  };
+}
+
+function createVideo({
+  id,
+  pubkey = "author",
+  displayTags,
+  tags,
+  rootCreatedAt,
+  created_at,
+  pointerKey,
+  pointerInfo,
+  shareUrl,
+  isPrivate = false,
+  isNsfw = false,
+} = {}) {
+  const video = {
+    id,
+    pubkey,
+    isPrivate,
+    isNsfw,
+  };
+
+  if (Array.isArray(displayTags)) {
+    video.displayTags = displayTags.slice();
+  }
+  if (Array.isArray(tags)) {
+    video.tags = tags.slice();
+  }
+  if (Number.isFinite(rootCreatedAt)) {
+    video.rootCreatedAt = Math.floor(rootCreatedAt);
+  }
+  if (Number.isFinite(created_at)) {
+    video.created_at = Math.floor(created_at);
+  }
+  if (typeof pointerKey === "string") {
+    video.pointerKey = pointerKey;
+  }
+  if (pointerInfo) {
+    video.pointerInfo = pointerInfo;
+  }
+  if (typeof shareUrl === "string") {
+    video.shareUrl = shareUrl;
+  }
+
+  return video;
+}
+
+test("orders similar videos by shared tags then timestamp", () => {
+  const activeVideo = createVideo({
+    id: "root-video",
+    displayTags: ["Art", "Music", "News"],
+  });
+
+  const candidateA = createVideo({
+    id: "video-a",
+    displayTags: ["art", "music"],
+    rootCreatedAt: 100,
+  });
+  const candidateB = createVideo({
+    id: "video-b",
+    displayTags: ["art"],
+    rootCreatedAt: 200,
+  });
+  const candidateC = createVideo({
+    id: "video-c",
+    displayTags: ["art", "music"],
+    rootCreatedAt: 50,
+  });
+
+  const app = createAppStub({
+    videos: [candidateA, candidateB, candidateC],
+  });
+
+  const matches = computeSimilarContent.call(app, { activeVideo, maxItems: 5 });
+  assert.equal(matches.length, 3);
+  assert.deepEqual(
+    matches.map((entry) => entry.video.id),
+    ["video-a", "video-c", "video-b"],
+  );
+  assert.deepEqual(
+    matches.map((entry) => entry.sharedTagCount),
+    [2, 2, 1],
+  );
+});
+
+test("returns no matches when the active video lacks tags", () => {
+  const activeVideo = createVideo({
+    id: "root-video",
+  });
+
+  const candidate = createVideo({
+    id: "video-a",
+    displayTags: ["art"],
+  });
+
+  const app = createAppStub({ videos: [candidate] });
+  const matches = computeSimilarContent.call(app, { activeVideo, maxItems: 5 });
+  assert.deepEqual(matches, []);
+});
+
+test("skips candidates without tag metadata", () => {
+  const activeVideo = createVideo({
+    id: "root-video",
+    displayTags: ["art"],
+  });
+
+  const candidateWithTags = createVideo({
+    id: "video-a",
+    displayTags: ["art"],
+  });
+  const candidateWithoutTags = createVideo({
+    id: "video-b",
+  });
+
+  const app = createAppStub({
+    videos: [candidateWithTags, candidateWithoutTags],
+  });
+
+  const matches = computeSimilarContent.call(app, { activeVideo, maxItems: 5 });
+  assert.equal(matches.length, 1);
+  assert.equal(matches[0].video.id, "video-a");
+});
+
+test("filters NSFW and private videos when NSFW content is disabled", () => {
+  const activeVideo = createVideo({
+    id: "root-video",
+    displayTags: ["art"],
+  });
+
+  const publicVideo = createVideo({
+    id: "video-public",
+    displayTags: ["art"],
+  });
+  const nsfwVideo = createVideo({
+    id: "video-nsfw",
+    displayTags: ["art"],
+    isNsfw: true,
+  });
+  const privateVideo = createVideo({
+    id: "video-private",
+    displayTags: ["art"],
+    isPrivate: true,
+  });
+
+  const app = createAppStub({
+    videos: [publicVideo, nsfwVideo, privateVideo],
+  });
+
+  const matches = computeSimilarContent.call(app, { activeVideo, maxItems: 5 });
+  assert.deepEqual(
+    matches.map((entry) => entry.video.id),
+    ["video-public"],
+  );
+});
diff --git a/tests/test-helpers/setup-localstorage.mjs b/tests/test-helpers/setup-localstorage.mjs
index ff110ed8..cfda0f66 100644
--- a/tests/test-helpers/setup-localstorage.mjs
+++ b/tests/test-helpers/setup-localstorage.mjs
@@ -2,6 +2,26 @@ if (typeof globalThis.window === "undefined") {
   globalThis.window = {};
 }
 
+if (typeof globalThis.self === "undefined") {
+  globalThis.self = globalThis;
+}
+
+if (typeof globalThis.WebSocket === "undefined") {
+  globalThis.WebSocket = class WebSocket {};
+}
+
+if (typeof globalThis.navigator === "undefined") {
+  globalThis.navigator = { userAgent: "node" };
+}
+
+if (typeof globalThis.window.WebSocket === "undefined") {
+  globalThis.window.WebSocket = globalThis.WebSocket;
+}
+
+if (typeof globalThis.window.navigator === "undefined") {
+  globalThis.window.navigator = globalThis.navigator;
+}
+
 if (typeof globalThis.localStorage === "undefined") {
   const store = new Map();
   globalThis.localStorage = {