diff --git a/chromium/manifest.json b/chromium/manifest.json
index d2c1949..ddbf931 100644
--- a/chromium/manifest.json
+++ b/chromium/manifest.json
@@ -5,7 +5,7 @@
   "description": "Send pages, selections, links, and files to the local Verstak browser inbox.",
   "author": "Verstak",
   "homepage_url": "https://git.mirv.top/verstak/verstak-browser-extension",
-  "permissions": ["contextMenus", "storage", "tabs"],
+  "permissions": ["alarms", "contextMenus", "idle", "storage", "tabs", "windows"],
   "host_permissions": ["http://127.0.0.1/*", "http://localhost/*"],
   "background": {
     "service_worker": "background.js"
diff --git a/firefox/manifest.json b/firefox/manifest.json
index 0ef91fc..cd47e23 100644
--- a/firefox/manifest.json
+++ b/firefox/manifest.json
@@ -15,9 +15,9 @@
       }
     }
   },
-  "permissions": ["contextMenus", "storage", "tabs", "http://127.0.0.1/*", "http://localhost/*"],
+  "permissions": ["alarms", "contextMenus", "idle", "storage", "tabs", "windows", "http://127.0.0.1/*", "http://localhost/*"],
   "background": {
-    "scripts": ["hostname.js", "protocol.js", "api.js", "queue.js", "i18n.js", "background.js"]
+    "scripts": ["hostname.js", "activity-tracker.js", "protocol.js", "api.js", "queue.js", "i18n.js", "background.js"]
   },
   "browser_action": {
     "default_popup": "popup/popup.html",
diff --git a/package.json b/package.json
index 66ff076..2474a85 100644
--- a/package.json
+++ b/package.json
@@ -5,7 +5,7 @@
   "description": "Verstak browser capture extension for Chromium and Firefox",
   "scripts": {
     "build": "node scripts/build-extension.js",
-    "test": "node scripts/test-hostname.js && node scripts/test-protocol.js && node scripts/test-i18n.js && node scripts/test-popup-settings.js && node scripts/test-popup-catalog-fallback.js && node scripts/test-background-i18n.js",
+    "test": "node scripts/test-hostname.js && node scripts/test-activity-tracker.js && node scripts/test-protocol.js && node scripts/test-i18n.js && node scripts/test-popup-settings.js && node scripts/test-popup-catalog-fallback.js && node scripts/test-background-i18n.js",
     "sign:firefox": "./scripts/sign-firefox-xpi.sh",
     "release:firefox": "./scripts/release-firefox-xpi.sh"
   },
diff --git a/scripts/build-extension.js b/scripts/build-extension.js
index 11b73bb..87bf596 100755
--- a/scripts/build-extension.js
+++ b/scripts/build-extension.js
@@ -52,6 +52,7 @@ mkdir(chromiumDist);
 copy(path.join(root, 'chromium', 'manifest.json'), path.join(chromiumDist, 'manifest.json'));
 concat([
   path.join(shared, 'hostname.js'),
+  path.join(shared, 'activity-tracker.js'),
   path.join(shared, 'protocol.js'),
   path.join(shared, 'api.js'),
   path.join(shared, 'queue.js'),
@@ -65,7 +66,7 @@ copyLocalization(chromiumDist);
 const firefoxDist = path.join(dist, 'firefox');
 mkdir(firefoxDist);
 copy(path.join(root, 'firefox', 'manifest.json'), path.join(firefoxDist, 'manifest.json'));
-for (const name of ['hostname.js', 'protocol.js', 'api.js', 'queue.js', 'i18n.js', 'background.js']) {
+for (const name of ['hostname.js', 'activity-tracker.js', 'protocol.js', 'api.js', 'queue.js', 'i18n.js', 'background.js']) {
   copy(path.join(shared, name), path.join(firefoxDist, name));
 }
 copyPopup(firefoxDist);
diff --git a/scripts/test-activity-tracker.js b/scripts/test-activity-tracker.js
new file mode 100644
index 0000000..7579586
--- /dev/null
+++ b/scripts/test-activity-tracker.js
@@ -0,0 +1,70 @@
+#!/usr/bin/env node
+const assert = require('assert');
+
+const hostname = require('../shared/hostname');
+const trackerApi = require('../shared/activity-tracker');
+
+async function main() {
+  const storage = trackerApi.createMemoryActivityStorage();
+  const sent = [];
+  let failSends = true;
+  const tracker = new trackerApi.DomainActivityTracker(storage, async (batch) => {
+    sent.push(JSON.parse(JSON.stringify(batch)));
+    if (failSends) throw new Error('offline');
+    return { status: 'accepted', batchId: batch.batchId };
+  });
+
+  await tracker.initialize();
+  await tracker.setEnabled(true);
+  await tracker.setActiveHostname('example.com', true, 0);
+  await tracker.checkpoint(600000);
+  await tracker.flush(600000);
+
+  let state = await tracker.getState();
+  assert.equal(state.pendingBatches.length, 1);
+  assert.equal(state.pendingBatches[0].entries[0].durationSeconds, 600);
+  const immutableFirstBatch = JSON.stringify(sent[0]);
+
+  await tracker.setActiveHostname('example.com', true, 900000);
+  await tracker.flush(900000);
+  state = await tracker.getState();
+  assert.equal(state.pendingBatches.length, 2, 'new activity must not mutate sent batch A');
+  assert.equal(state.pendingBatches[1].entries[0].durationSeconds, 300);
+
+  failSends = false;
+  await tracker.retryPending();
+  state = await tracker.getState();
+  assert.equal(state.pendingBatches.length, 0);
+  assert.ok(state.acknowledgedIds.length >= 2);
+  assert.equal(JSON.stringify(sent[1]), immutableFirstBatch, 'retry must resend an immutable batch A payload');
+
+  const clockTracker = new trackerApi.DomainActivityTracker(trackerApi.createMemoryActivityStorage(), async () => ({ status: 'accepted' }));
+  await clockTracker.initialize();
+  await clockTracker.setEnabled(true);
+  await clockTracker.setActiveHostname('example.com', true, 0);
+  await clockTracker.checkpoint(8 * 60 * 60 * 1000);
+  state = await clockTracker.getState();
+  assert.equal(state.activeAccumulator['example.com'].durationMs, 0, 'sleep-sized gap must be discarded');
+  await clockTracker.checkpoint(8 * 60 * 60 * 1000 + 5 * 60 * 1000);
+  state = await clockTracker.getState();
+  assert.equal(state.activeAccumulator['example.com'].durationMs, 300000);
+  await clockTracker.checkpoint(1000000);
+  state = await clockTracker.getState();
+  assert.equal(state.activeAccumulator['example.com'].durationMs, 0, 'clock rollback must reset the ambiguous interval');
+
+  assert.equal(trackerApi.isExcludedHostname('video.youtube.com', ['youtube.com']), true);
+  assert.equal(trackerApi.isExcludedHostname('youtube.com.evil.test', ['youtube.com']), false);
+  assert.equal(trackerApi.isExcludedHostname(hostname.normalizeHostnameV1('пример.рф'), ['пример.рф']), true);
+
+  await tracker.setEnabled(false);
+  state = await tracker.getState();
+  assert.deepEqual(state.activeAccumulator, {});
+  assert.deepEqual(state.pendingBatches, []);
+  assert.equal(JSON.stringify(state).includes('https://'), false);
+  console.log('browser activity tracker tests passed');
+}
+
+main().catch((error) => {
+  console.error(error);
+  process.exit(1);
+});
diff --git a/scripts/test-background-i18n.js b/scripts/test-background-i18n.js
index e37f277..0fa2b01 100644
--- a/scripts/test-background-i18n.js
+++ b/scripts/test-background-i18n.js
@@ -49,7 +49,13 @@ const browser = {
     onMessage: { addListener(listener) { messageListener = listener; } },
   },
   i18n: { getUILanguage() { return 'en-US'; } },
-  tabs: { query() { return Promise.resolve([]); } },
+  tabs: {
+    query() { return Promise.resolve([{ id: 7, windowId: 1, url: 'https://example.com/private-path', title: 'Private title' }]); },
+    get() { return Promise.resolve({ id: 7, windowId: 1, url: 'https://example.com/private-path', title: 'Private title' }); },
+    onActivated: { addListener() {} },
+    onUpdated: { addListener() {} },
+    onRemoved: { addListener() {} },
+  },
 };
 
 function fetchCatalog(url) {
@@ -69,7 +75,7 @@ const context = vm.createContext({
   clearTimeout,
 });
 context.globalThis = context;
-for (const file of ['protocol.js', 'api.js', 'queue.js', 'i18n.js', 'background.js']) {
+for (const file of ['hostname.js', 'activity-tracker.js', 'protocol.js', 'api.js', 'queue.js', 'i18n.js', 'background.js']) {
   vm.runInContext(fs.readFileSync(path.join(root, 'shared', file), 'utf8'), context, { filename: file });
 }
 
@@ -92,6 +98,22 @@ function sendMessage(message) {
     'Отправить ссылку в Верстак',
   ]);
 
+  const trackingState = await sendMessage({
+    type: 'verstak.capture',
+    action: 'saveSettings',
+    settings: {
+      receiverUrl: state.settings.receiverUrl,
+      receiverToken: state.settings.receiverToken,
+      language: 'en',
+      passiveActivityEnabled: true,
+      passiveActivityExcludedDomains: [],
+    },
+  });
+  assert.strictEqual(trackingState.settings.passiveActivityEnabled, true);
+  assert.ok(trackingState.activityState.activeAccumulator['example.com']);
+  assert.equal(JSON.stringify(trackingState.activityState).includes('private-path'), false);
+  assert.equal(JSON.stringify(trackingState.activityState).includes('Private title'), false);
+
   const nextState = await sendMessage({
     type: 'verstak.capture',
     action: 'saveSettings',
diff --git a/scripts/test-popup-settings.js b/scripts/test-popup-settings.js
index 062f4ad..57f034f 100644
--- a/scripts/test-popup-settings.js
+++ b/scripts/test-popup-settings.js
@@ -35,10 +35,12 @@ const elements = {};
   'receiver-token-input',
   'file-input',
   'pending-count',
+  'activity-pending-count',
   'status-dot',
   'subtitle',
   'receiver-label',
   'pending-label',
+  'activity-pending-label',
   'url-label',
   'capture-page',
   'capture-file',
@@ -53,6 +55,11 @@ const elements = {};
   'language-ru-option',
   'save-settings',
   'context-menu-hint',
+  'passive-activity-enabled',
+  'passive-activity-label',
+  'passive-activity-disclosure',
+  'passive-activity-exclusions-label',
+  'passive-activity-exclusions',
 ].forEach((id) => {
   elements[id] = new Element();
 });
@@ -63,6 +70,8 @@ const initialState = {
     receiverUrl: 'http://127.0.0.1:47731/api/browser-inbox/v1/captures',
     receiverToken: 'persisted-token',
     language: 'system',
+    passiveActivityEnabled: false,
+    passiveActivityExcludedDomains: ['youtube.com'],
   },
   pendingCount: 0,
   status: {},
@@ -112,6 +121,8 @@ async function flush() {
   assert.strictEqual(elements['receiver-input'].value, initialState.settings.receiverUrl);
   assert.strictEqual(elements['receiver-token-input'].value, initialState.settings.receiverToken);
   assert.strictEqual(elements['language-select'].value, 'system');
+  assert.strictEqual(elements['passive-activity-enabled'].checked, false);
+  assert.strictEqual(elements['passive-activity-exclusions'].value, 'youtube.com');
   assert.strictEqual(elements['capture-page'].textContent, 'Отправить страницу');
   assert.strictEqual(elements['receiver-state'].textContent, 'Неизвестно');
   assert.strictEqual(document.documentElement.lang, 'ru');
@@ -129,9 +140,13 @@ async function flush() {
   assert.strictEqual(savedSettings.language, 'en');
   assert.strictEqual(savedSettings.receiverUrl, initialState.settings.receiverUrl);
   assert.strictEqual(savedSettings.receiverToken, initialState.settings.receiverToken);
+  assert.strictEqual(savedSettings.passiveActivityEnabled, false);
+  assert.deepStrictEqual(Array.from(savedSettings.passiveActivityExcludedDomains), ['youtube.com']);
 
   elements['receiver-input'].value = 'http://127.0.0.1:47731/api/browser-inbox/v1/captures';
   elements['receiver-token-input'].value = 'new-token';
+  elements['passive-activity-enabled'].checked = true;
+  elements['passive-activity-exclusions'].value = 'youtube.com\nx.com';
   elements['save-settings'].click();
   await flush();
 
@@ -139,6 +154,8 @@ async function flush() {
   assert.strictEqual(savedSettings.receiverUrl, 'http://127.0.0.1:47731/api/browser-inbox/v1/captures');
   assert.strictEqual(savedSettings.receiverToken, 'new-token');
   assert.strictEqual(savedSettings.language, 'en');
+  assert.strictEqual(savedSettings.passiveActivityEnabled, true);
+  assert.deepStrictEqual(Array.from(savedSettings.passiveActivityExcludedDomains), ['youtube.com', 'x.com']);
   console.log('browser extension popup localization/settings tests passed');
 })().catch((error) => {
   console.error(error);
diff --git a/scripts/test-protocol.js b/scripts/test-protocol.js
index 5f78042..9df6c51 100755
--- a/scripts/test-protocol.js
+++ b/scripts/test-protocol.js
@@ -52,6 +52,20 @@ const fetchOk = (url, options) => {
   return Promise.resolve({ status: 202, json: () => Promise.resolve({ status: 'accepted' }) });
 };
 
+const activityBatch = {
+  schemaVersion: 1,
+  batchId: 'activity-batch-id',
+  createdAt: '2026-07-12T10:05:00.000Z',
+  source: 'verstak-browser-extension',
+  entries: [{
+    hostname: 'example.com',
+    startedAt: '2026-07-12T10:00:00.000Z',
+    endedAt: '2026-07-12T10:05:00.000Z',
+    durationSeconds: 300,
+    url: 'https://must-not-be-sent.example'
+  }]
+};
+
 globalThis.VerstakBrowser.sendCapture('http://127.0.0.1:47731/api/browser-inbox/v1/captures', 'token', page, fetchOk)
   .then((result) => {
     assert.equal(result.status, 'accepted');
@@ -59,6 +73,17 @@ globalThis.VerstakBrowser.sendCapture('http://127.0.0.1:47731/api/browser-inbox/
     assert.equal(request.options.headers['X-Verstak-Receiver-Token'], 'token');
     assert.equal(JSON.parse(request.options.body).captureId, 'test-capture-id');
   })
+  .then(() => {
+    return globalThis.VerstakBrowser.sendActivityBatch('http://127.0.0.1:47731/api/browser-inbox/v1/captures', 'token', activityBatch, fetchOk)
+      .then((result) => {
+        assert.equal(result.status, 'accepted');
+        assert.equal(request.url, 'http://127.0.0.1:47731/api/browser-activity/v1/batches');
+        const body = JSON.parse(request.options.body);
+        assert.equal(body.batchId, 'activity-batch-id');
+        assert.equal(body.entries[0].hostname, 'example.com');
+        assert.equal(Object.prototype.hasOwnProperty.call(body.entries[0], 'url'), false);
+      });
+  })
   .then(() => {
     const queue = new queueApi.CaptureQueue(queueApi.createMemoryStorage());
     return queue.enqueue(page)
diff --git a/shared/activity-tracker.js b/shared/activity-tracker.js
new file mode 100644
index 0000000..ac51aa1
--- /dev/null
+++ b/shared/activity-tracker.js
@@ -0,0 +1,283 @@
+(function (root) {
+  'use strict';
+
+  var ACTIVITY_STATE_KEY = 'verstak.domainActivity.v1';
+  var MAX_CHECKPOINT_GAP_MS = 10 * 60 * 1000;
+  var ACK_RETENTION_MS = 30 * 24 * 60 * 60 * 1000;
+  var MAX_ACKNOWLEDGED_IDS = 1000;
+
+  function createMemoryActivityStorage(seed) {
+    var state = Object.assign({}, seed || {});
+    return {
+      get: function (key) {
+        return Promise.resolve(state[key]);
+      },
+      set: function (key, value) {
+        state[key] = value;
+        return Promise.resolve();
+      }
+    };
+  }
+
+  function browserActivityStorageAdapter(browserApi) {
+    var storage = browserApi && browserApi.storage && browserApi.storage.local;
+    if (!storage) return createMemoryActivityStorage();
+    return {
+      get: function (key) {
+        return storage.get(key).then(function (result) { return result && result[key]; });
+      },
+      set: function (key, value) {
+        var patch = {};
+        patch[key] = value;
+        return storage.set(patch);
+      }
+    };
+  }
+
+  function clone(value) {
+    return JSON.parse(JSON.stringify(value));
+  }
+
+  function isFiniteNumber(value) {
+    return typeof value === 'number' && Number.isFinite(value);
+  }
+
+  function initialState() {
+    return {
+      activeAccumulator: {},
+      pendingBatches: [],
+      acknowledgedIds: []
+    };
+  }
+
+  function normalizedState(value) {
+    var state = value && typeof value === 'object' ? value : {};
+    return {
+      activeAccumulator: state.activeAccumulator && typeof state.activeAccumulator === 'object' ? state.activeAccumulator : {},
+      pendingBatches: Array.isArray(state.pendingBatches) ? state.pendingBatches : [],
+      acknowledgedIds: Array.isArray(state.acknowledgedIds) ? state.acknowledgedIds : []
+    };
+  }
+
+  function batchId(now) {
+    var cryptoObj = root.crypto;
+    if (cryptoObj && typeof cryptoObj.randomUUID === 'function') return cryptoObj.randomUUID();
+    return 'activity-' + String(now) + '-' + Math.random().toString(36).slice(2);
+  }
+
+  function toISOString(time) {
+    return new Date(time).toISOString();
+  }
+
+  function isExcludedHostname(hostname, excludedDomains) {
+    var normalizer = root.VerstakBrowser && root.VerstakBrowser.normalizeHostnameV1;
+    var canonicalHostname = typeof normalizer === 'function' ? normalizer(hostname) : '';
+    if (!canonicalHostname) return true;
+    return (Array.isArray(excludedDomains) ? excludedDomains : []).some(function (value) {
+      var excluded = typeof normalizer === 'function' ? normalizer(value) : '';
+      return excluded && (canonicalHostname === excluded || canonicalHostname.slice(-(excluded.length + 1)) === '.' + excluded);
+    });
+  }
+
+  function DomainActivityTracker(storage, sender, options) {
+    options = options || {};
+    this.storage = storage || createMemoryActivityStorage();
+    this.sender = typeof sender === 'function' ? sender : function () { return Promise.reject(new Error('activity sender unavailable')); };
+    this.maxCheckpointGapMs = isFiniteNumber(options.maxCheckpointGapMs) ? options.maxCheckpointGapMs : MAX_CHECKPOINT_GAP_MS;
+    this.now = typeof options.now === 'function' ? options.now : function () { return Date.now(); };
+    this.state = initialState();
+    this.enabled = false;
+    this.activeHostname = '';
+    this.serial = Promise.resolve();
+  }
+
+  DomainActivityTracker.prototype.enqueue = function (operation) {
+    var next = this.serial.then(operation, operation);
+    this.serial = next.catch(function () {});
+    return next;
+  };
+
+  DomainActivityTracker.prototype.initialize = function () {
+    var self = this;
+    return this.enqueue(function () {
+      return self.storage.get(ACTIVITY_STATE_KEY).then(function (value) {
+        self.state = normalizedState(value);
+        self.pruneAcknowledged(self.now());
+        return self.persist().then(function () { return self.getStateUnsafe(); });
+      });
+    });
+  };
+
+  DomainActivityTracker.prototype.getState = function () {
+    var self = this;
+    return this.enqueue(function () { return self.getStateUnsafe(); });
+  };
+
+  DomainActivityTracker.prototype.getStateUnsafe = function () {
+    return clone(this.state);
+  };
+
+  DomainActivityTracker.prototype.persist = function () {
+    return this.storage.set(ACTIVITY_STATE_KEY, clone(this.state));
+  };
+
+  DomainActivityTracker.prototype.setEnabled = function (enabled) {
+    var self = this;
+    return this.enqueue(function () {
+      self.enabled = enabled === true;
+      if (!self.enabled) {
+        self.activeHostname = '';
+        self.state.activeAccumulator = {};
+        self.state.pendingBatches = [];
+      }
+      return self.persist().then(function () { return self.getStateUnsafe(); });
+    });
+  };
+
+  DomainActivityTracker.prototype.setActiveHostname = function (hostname, active, observedAt) {
+    var self = this;
+    var now = isFiniteNumber(observedAt) ? observedAt : this.now();
+    return this.enqueue(function () {
+      if (!self.enabled || !active || !hostname) {
+        self.checkpointUnsafe(now);
+        self.activeHostname = '';
+        return self.persist().then(function () { return self.getStateUnsafe(); });
+      }
+      self.checkpointUnsafe(now);
+      self.activeHostname = hostname;
+      self.ensureAccumulator(hostname, now);
+      return self.persist().then(function () { return self.getStateUnsafe(); });
+    });
+  };
+
+  DomainActivityTracker.prototype.checkpoint = function (observedAt) {
+    var self = this;
+    var now = isFiniteNumber(observedAt) ? observedAt : this.now();
+    return this.enqueue(function () {
+      self.checkpointUnsafe(now);
+      return self.persist().then(function () { return self.getStateUnsafe(); });
+    });
+  };
+
+  DomainActivityTracker.prototype.ensureAccumulator = function (hostname, now) {
+    if (!this.state.activeAccumulator[hostname]) {
+      this.state.activeAccumulator[hostname] = {
+        hostname: hostname,
+        startedAt: now,
+        lastCheckpointAt: now,
+        durationMs: 0
+      };
+    }
+    return this.state.activeAccumulator[hostname];
+  };
+
+  DomainActivityTracker.prototype.checkpointUnsafe = function (now) {
+    if (!this.enabled || !this.activeHostname) return;
+    var accumulator = this.ensureAccumulator(this.activeHostname, now);
+    var previous = accumulator.lastCheckpointAt;
+    var delta = now - previous;
+    if (!isFiniteNumber(previous) || delta < 0 || delta > this.maxCheckpointGapMs) {
+      accumulator.startedAt = now;
+      accumulator.lastCheckpointAt = now;
+      accumulator.durationMs = 0;
+      return;
+    }
+    if (delta === 0) return;
+    accumulator.durationMs += delta;
+    accumulator.lastCheckpointAt = now;
+  };
+
+  DomainActivityTracker.prototype.flush = function (observedAt) {
+    var self = this;
+    var now = isFiniteNumber(observedAt) ? observedAt : this.now();
+    return this.enqueue(function () {
+      if (!self.enabled) return self.getStateUnsafe();
+      self.checkpointUnsafe(now);
+      var entries = [];
+      Object.keys(self.state.activeAccumulator).forEach(function (hostname) {
+        var accumulator = self.state.activeAccumulator[hostname];
+        var durationSeconds = Math.floor(Number(accumulator.durationMs || 0) / 1000);
+        if (durationSeconds < 1) return;
+        entries.push({
+          hostname: accumulator.hostname,
+          startedAt: toISOString(accumulator.startedAt),
+          endedAt: toISOString(accumulator.lastCheckpointAt),
+          durationSeconds: durationSeconds
+        });
+      });
+      if (entries.length) {
+        self.state.pendingBatches.push({
+          schemaVersion: 1,
+          batchId: batchId(now),
+          createdAt: toISOString(now),
+          source: 'verstak-browser-extension',
+          entries: entries
+        });
+        self.state.activeAccumulator = {};
+        if (self.activeHostname) self.ensureAccumulator(self.activeHostname, now);
+      }
+      return self.persist().then(function () {
+        return self.deliverPendingUnsafe(now);
+      });
+    });
+  };
+
+  DomainActivityTracker.prototype.retryPending = function () {
+    var self = this;
+    return this.enqueue(function () {
+      if (!self.enabled) return self.getStateUnsafe();
+      return self.deliverPendingUnsafe(self.now());
+    });
+  };
+
+  DomainActivityTracker.prototype.deliverPendingUnsafe = function (now) {
+    var self = this;
+    var pending = this.state.pendingBatches.slice();
+    return pending.reduce(function (chain, batch) {
+      return chain.then(function () {
+        if (!self.hasPendingBatch(batch.batchId)) return undefined;
+        var immutableBatch = clone(batch);
+        return self.sender(immutableBatch).then(function (result) {
+          if (result && result.batchId && result.batchId !== batch.batchId) {
+            throw new Error('receiver acknowledged a different activity batch');
+          }
+          self.state.pendingBatches = self.state.pendingBatches.filter(function (item) { return item.batchId !== batch.batchId; });
+          self.state.acknowledgedIds.push({ id: batch.batchId, acknowledgedAt: toISOString(now) });
+          self.pruneAcknowledged(now);
+          return self.persist();
+        });
+      });
+    }, Promise.resolve()).then(function () {
+      return self.getStateUnsafe();
+    }).catch(function () {
+      return self.persist().then(function () { return self.getStateUnsafe(); });
+    });
+  };
+
+  DomainActivityTracker.prototype.hasPendingBatch = function (batchID) {
+    return this.state.pendingBatches.some(function (batch) { return batch.batchId === batchID; });
+  };
+
+  DomainActivityTracker.prototype.pruneAcknowledged = function (now) {
+    var cutoff = now - ACK_RETENTION_MS;
+    var seen = {};
+    this.state.acknowledgedIds = this.state.acknowledgedIds.filter(function (entry) {
+      var timestamp = Date.parse(entry && entry.acknowledgedAt);
+      if (!entry || !entry.id || !Number.isFinite(timestamp) || timestamp < cutoff || seen[entry.id]) return false;
+      seen[entry.id] = true;
+      return true;
+    }).slice(-MAX_ACKNOWLEDGED_IDS);
+  };
+
+  var api = {
+    ACTIVITY_STATE_KEY: ACTIVITY_STATE_KEY,
+    MAX_CHECKPOINT_GAP_MS: MAX_CHECKPOINT_GAP_MS,
+    createMemoryActivityStorage: createMemoryActivityStorage,
+    browserActivityStorageAdapter: browserActivityStorageAdapter,
+    DomainActivityTracker: DomainActivityTracker,
+    isExcludedHostname: isExcludedHostname
+  };
+
+  root.VerstakBrowser = Object.assign(root.VerstakBrowser || {}, api);
+  if (typeof module !== 'undefined') module.exports = api;
+})(typeof globalThis !== 'undefined' ? globalThis : this);
diff --git a/shared/api.js b/shared/api.js
index 54c53dc..6ac2bb8 100644
--- a/shared/api.js
+++ b/shared/api.js
@@ -20,7 +20,63 @@
     });
   }
 
-  var api = { sendCapture: sendCapture };
+  function activityReceiverURL(captureReceiverURL) {
+    var protocol = root.VerstakBrowser || {};
+    var receiverURL = String(captureReceiverURL || protocol.DEFAULT_RECEIVER_URL || '').trim();
+    var capturePath = '/api/browser-inbox/v1/captures';
+    if (receiverURL.slice(-capturePath.length) === capturePath) {
+      return receiverURL.slice(0, -capturePath.length) + '/api/browser-activity/v1/batches';
+    }
+    return protocol.DEFAULT_ACTIVITY_URL;
+  }
+
+  function safeActivityBatch(payload) {
+    if (!payload || payload.schemaVersion !== 1 || !payload.batchId || !payload.createdAt || !payload.source || !Array.isArray(payload.entries) || payload.entries.length === 0) {
+      throw new Error('invalid activity batch');
+    }
+    var entries = payload.entries.map(function (entry) {
+      if (!entry || !entry.hostname || !entry.startedAt || !entry.endedAt || !Number.isFinite(Number(entry.durationSeconds)) || Number(entry.durationSeconds) <= 0) {
+        throw new Error('invalid activity batch entry');
+      }
+      return {
+        hostname: String(entry.hostname),
+        startedAt: String(entry.startedAt),
+        endedAt: String(entry.endedAt),
+        durationSeconds: Math.floor(Number(entry.durationSeconds))
+      };
+    });
+    return {
+      schemaVersion: 1,
+      batchId: String(payload.batchId),
+      createdAt: String(payload.createdAt),
+      source: String(payload.source),
+      entries: entries
+    };
+  }
+
+  function sendActivityBatch(captureReceiverURL, token, payload, fetchImpl) {
+    var batch = safeActivityBatch(payload);
+    var fetchFn = fetchImpl || root.fetch;
+    if (typeof fetchFn !== 'function') return Promise.reject(new Error('fetch unavailable'));
+    return fetchFn(activityReceiverURL(captureReceiverURL), {
+      method: 'POST',
+      headers: Object.assign({
+        'Content-Type': 'application/json'
+      }, token ? { 'X-Verstak-Receiver-Token': token } : {}),
+      body: JSON.stringify(batch)
+    }).then(function (response) {
+      if (!response || response.status < 200 || response.status >= 300) {
+        throw new Error('receiver rejected activity batch: HTTP ' + (response && response.status));
+      }
+      return response.json ? response.json() : { status: 'accepted', batchId: batch.batchId };
+    });
+  }
+
+  var api = {
+    sendCapture: sendCapture,
+    sendActivityBatch: sendActivityBatch,
+    activityReceiverURL: activityReceiverURL
+  };
   root.VerstakBrowser = Object.assign(root.VerstakBrowser || {}, api);
   if (typeof module !== 'undefined') module.exports = api;
 })(typeof globalThis !== 'undefined' ? globalThis : this);
diff --git a/shared/background.js b/shared/background.js
index dfdbf41..32f3028 100644
--- a/shared/background.js
+++ b/shared/background.js
@@ -4,19 +4,34 @@
   var ext = typeof browser !== 'undefined' ? browser : chrome;
   var protocol = globalThis.VerstakBrowser;
   var queue = new protocol.CaptureQueue(protocol.browserStorageAdapter(ext));
+  var activityTracker = new protocol.DomainActivityTracker(
+    protocol.browserActivityStorageAdapter(ext),
+    function (batch) {
+      return getSettings().then(function (settings) {
+        return protocol.sendActivityBatch(settings.receiverUrl, settings.receiverToken, batch);
+      });
+    }
+  );
   var i18n = globalThis.VerstakBrowserI18n;
   var DEFAULT_SETTINGS = {
     receiverUrl: protocol.DEFAULT_RECEIVER_URL,
     receiverToken: '',
-    language: 'system'
+    language: 'system',
+    passiveActivityEnabled: false,
+    passiveActivityExcludedDomains: []
   };
   var STATUS_KEY = 'verstak.status';
+  var ACTIVITY_FLUSH_ALARM = 'verstak-domain-activity-flush';
   var localeCatalogs = null;
+  var focusedWindowID = null;
+  var activeTabID = null;
 
   function getSettings() {
     return ext.storage.local.get('settings').then(function (result) {
       var settings = Object.assign({}, DEFAULT_SETTINGS, result && result.settings || {});
       settings.language = i18n.normalizePreference(settings.language);
+      settings.passiveActivityEnabled = settings.passiveActivityEnabled === true;
+      settings.passiveActivityExcludedDomains = normalizeExcludedDomains(settings.passiveActivityExcludedDomains);
       return settings;
     });
   }
@@ -24,9 +39,23 @@
   function saveSettings(settings) {
     settings = Object.assign({}, DEFAULT_SETTINGS, settings || {});
     settings.language = i18n.normalizePreference(settings.language);
+    settings.passiveActivityEnabled = settings.passiveActivityEnabled === true;
+    settings.passiveActivityExcludedDomains = normalizeExcludedDomains(settings.passiveActivityExcludedDomains);
     return ext.storage.local.set({ settings: settings });
   }
 
+  function normalizeExcludedDomains(value) {
+    var values = Array.isArray(value) ? value : String(value || '').split(/[\n,]/);
+    var seen = {};
+    return values.map(function (item) {
+      return protocol.normalizeHostnameV1(String(item || '').trim());
+    }).filter(function (item) {
+      if (!item || seen[item]) return false;
+      seen[item] = true;
+      return true;
+    });
+  }
+
   function loadLocaleCatalogs() {
     if (localeCatalogs) return localeCatalogs;
     localeCatalogs = i18n.loadCatalogs(function (locale) {
@@ -68,6 +97,58 @@
     });
   }
 
+  function isFocusedWindow(windowID) {
+    return focusedWindowID == null || focusedWindowID === windowID;
+  }
+
+  function trackTab(tab, settings) {
+    if (!settings.passiveActivityEnabled || !tab || !isFocusedWindow(tab.windowId)) {
+      return activityTracker.setActiveHostname('', false);
+    }
+    activeTabID = tab.id == null ? activeTabID : tab.id;
+    var hostname = protocol.normalizeURLHostnameV1(tab.url || '');
+    if (!hostname || protocol.isExcludedHostname(hostname, settings.passiveActivityExcludedDomains)) {
+      return activityTracker.setActiveHostname('', false);
+    }
+    return activityTracker.setActiveHostname(hostname, true);
+  }
+
+  function refreshFocusedTab(settings) {
+    return activeTab().then(function (tab) {
+      return trackTab(tab, settings);
+    }).catch(function () {
+      return activityTracker.setActiveHostname('', false);
+    });
+  }
+
+  function configurePassiveActivity(settings) {
+    return activityTracker.setEnabled(settings.passiveActivityEnabled).then(function () {
+      if (!settings.passiveActivityEnabled) return undefined;
+      return refreshFocusedTab(settings);
+    });
+  }
+
+  function flushPassiveActivity() {
+    return getSettings().then(function (settings) {
+      if (!settings.passiveActivityEnabled) return activityTracker.setEnabled(false);
+      return activityTracker.setEnabled(true).then(function () {
+        return refreshFocusedTab(settings);
+      }).then(function () {
+        return activityTracker.flush();
+      });
+    });
+  }
+
+  function setupPassiveActivity() {
+    if (ext.alarms && ext.alarms.create) {
+      ext.alarms.create(ACTIVITY_FLUSH_ALARM, { periodInMinutes: 5 });
+    }
+    if (ext.idle && ext.idle.setDetectionInterval) {
+      ext.idle.setDetectionInterval(60);
+    }
+    return getSettings().then(configurePassiveActivity);
+  }
+
   function captureFromInfo(kind, info, tab) {
     return protocol.buildCapture({
       kind: kind,
@@ -123,11 +204,14 @@
     return Promise.all([
       getSettings(),
       queue.list(),
-      ext.storage.local.get(STATUS_KEY)
+      ext.storage.local.get(STATUS_KEY),
+      activityTracker.getState()
     ]).then(function (results) {
       return {
         settings: results[0],
         pendingCount: results[1].length,
+        pendingActivityCount: results[3].pendingBatches.length,
+        activityState: results[3],
         status: results[2] && results[2][STATUS_KEY] || {}
       };
     });
@@ -170,19 +254,24 @@
   }
 
   function handleMessage(message) {
-    if (!message || message.type !== 'verstak.capture') return Promise.resolve(undefined);
-    if (message.action === 'getState') return getState();
-    if (message.action === 'saveSettings') {
-      return saveSettings(message.settings).then(function () {
-        return setupContextMenus();
-      }).then(function () {
-        return setStatus({ receiverReachable: null, lastResult: 'settings-saved', lastError: '' });
+    return ready.then(function () {
+      if (!message || message.type !== 'verstak.capture') return undefined;
+      if (message.action === 'getState') return getState();
+      if (message.action === 'saveSettings') {
+        return saveSettings(message.settings).then(function () {
+          return setupContextMenus();
+        }).then(function () {
+          return getSettings().then(configurePassiveActivity);
+        }).then(function () {
+          return setStatus({ receiverReachable: null, lastResult: 'settings-saved', lastError: '' });
+        }).then(getState);
+      }
+      if (message.action === 'retryPending') return retryPending().then(getState);
+      if (message.action === 'retryPendingActivity') return activityTracker.retryPending().then(getState);
+      return activeTab().then(function (tab) {
+        return sendOrQueue(captureFromInfo(message.kind || 'page', message, tab));
       }).then(getState);
-    }
-    if (message.action === 'retryPending') return retryPending().then(getState);
-    return activeTab().then(function (tab) {
-      return sendOrQueue(captureFromInfo(message.kind || 'page', message, tab));
-    }).then(getState);
+    });
   }
 
   ext.runtime.onMessage.addListener(function (message, sender, sendResponse) {
@@ -191,4 +280,63 @@
     });
     return true;
   });
+
+  if (ext.tabs && ext.tabs.onActivated) {
+    ext.tabs.onActivated.addListener(function (info) {
+      if (!isFocusedWindow(info.windowId) || !ext.tabs.get) return;
+      activeTabID = info.tabId;
+      ready.then(function () { return getSettings(); }).then(function (settings) {
+        return ext.tabs.get(info.tabId).then(function (tab) { return trackTab(tab, settings); });
+      }).catch(function () {});
+    });
+  }
+
+  if (ext.tabs && ext.tabs.onUpdated) {
+    ext.tabs.onUpdated.addListener(function (tabID, changeInfo, tab) {
+      if (tabID !== activeTabID || (!changeInfo.url && !(tab && tab.url))) return;
+      ready.then(function () { return getSettings(); }).then(function (settings) {
+        return trackTab(tab || { id: tabID, url: changeInfo.url }, settings);
+      }).catch(function () {});
+    });
+  }
+
+  if (ext.windows && ext.windows.onFocusChanged) {
+    ext.windows.onFocusChanged.addListener(function (windowID) {
+      focusedWindowID = windowID;
+      if (windowID === (ext.windows.WINDOW_ID_NONE == null ? -1 : ext.windows.WINDOW_ID_NONE)) {
+        activityTracker.setActiveHostname('', false).catch(function () {});
+        return;
+      }
+      ready.then(function () { return getSettings(); }).then(refreshFocusedTab).catch(function () {});
+    });
+  }
+
+  if (ext.idle && ext.idle.onStateChanged) {
+    ext.idle.onStateChanged.addListener(function (state) {
+      if (state === 'active') {
+        ready.then(function () { return getSettings(); }).then(refreshFocusedTab).catch(function () {});
+        return;
+      }
+      activityTracker.setActiveHostname('', false).catch(function () {});
+    });
+  }
+
+  if (ext.alarms && ext.alarms.onAlarm) {
+    ext.alarms.onAlarm.addListener(function (alarm) {
+      if (alarm && alarm.name === ACTIVITY_FLUSH_ALARM) flushPassiveActivity().catch(function () {});
+    });
+  }
+
+  if (ext.tabs && ext.tabs.onRemoved) {
+    ext.tabs.onRemoved.addListener(function (tabID) {
+      if (tabID === activeTabID) {
+        activeTabID = null;
+        activityTracker.setActiveHostname('', false).catch(function () {});
+      }
+    });
+  }
+
+  var ready = activityTracker.initialize().then(setupPassiveActivity).catch(function (error) {
+    console.warn('[verstak] passive activity initialization failed:', error);
+  });
 })();
diff --git a/shared/locales/en.json b/shared/locales/en.json
index 5785e83..d5b6ee7 100644
--- a/shared/locales/en.json
+++ b/shared/locales/en.json
@@ -2,16 +2,20 @@
   "popup.subtitle": "Browser Inbox",
   "label.receiver": "Receiver",
   "label.pending": "Pending",
+  "label.activityPending": "Activity batches",
   "label.url": "URL",
   "label.file": "File",
   "label.receiverUrl": "Receiver URL",
   "label.pairingToken": "Pairing token",
   "label.language": "Language",
+  "label.passiveActivity": "Track active domain time",
+  "label.passiveActivityExclusions": "Excluded domains",
   "action.sendPage": "Send Page",
   "action.sendFile": "Send File",
   "action.retryPending": "Retry Pending",
   "action.save": "Save",
   "hint.contextMenu": "Selection and link captures are available from the page context menu.",
+  "hint.passiveActivityDisclosure": "Optional. Collects only the active domain and time spent there. It never sends page URLs, titles, text, keystrokes, or page contents.",
   "receiver.online": "Online",
   "receiver.offline": "Offline",
   "receiver.unknown": "Unknown",
diff --git a/shared/locales/ru.json b/shared/locales/ru.json
index 059ef08..9f010a1 100644
--- a/shared/locales/ru.json
+++ b/shared/locales/ru.json
@@ -2,16 +2,20 @@
   "popup.subtitle": "Входящие из браузера",
   "label.receiver": "Приёмник",
   "label.pending": "В очереди",
+  "label.activityPending": "Пакеты активности",
   "label.url": "URL",
   "label.file": "Файл",
   "label.receiverUrl": "URL приёмника",
   "label.pairingToken": "Токен сопряжения",
   "label.language": "Язык",
+  "label.passiveActivity": "Учитывать время на активном домене",
+  "label.passiveActivityExclusions": "Исключённые домены",
   "action.sendPage": "Отправить страницу",
   "action.sendFile": "Отправить файл",
   "action.retryPending": "Повторить отправку",
   "action.save": "Сохранить",
   "hint.contextMenu": "Выделение и ссылки можно отправить через контекстное меню страницы.",
+  "hint.passiveActivityDisclosure": "Необязательно. Собираются только активный домен и время на нём. URL страниц, заголовки, текст, нажатия клавиш и содержимое страниц не отправляются.",
   "receiver.online": "Доступен",
   "receiver.offline": "Недоступен",
   "receiver.unknown": "Неизвестно",
diff --git a/shared/popup/popup.css b/shared/popup/popup.css
index daa6b3b..20254ef 100644
--- a/shared/popup/popup.css
+++ b/shared/popup/popup.css
@@ -126,6 +126,19 @@ input {
   color: #e5e7eb;
 }
 
+textarea {
+  box-sizing: border-box;
+  width: 100%;
+  margin-top: 5px;
+  border: 1px solid #374151;
+  border-radius: 4px;
+  padding: 7px 8px;
+  resize: vertical;
+  background: #0f172a;
+  color: #e5e7eb;
+  font: inherit;
+}
+
 select {
   box-sizing: border-box;
   width: 100%;
@@ -142,6 +155,23 @@ input[type="file"] {
   font-size: 12px;
 }
 
+.tracking-toggle {
+  display: flex;
+  align-items: center;
+  gap: 7px;
+  color: #e8ecf3 !important;
+  cursor: pointer;
+}
+
+.tracking-toggle input {
+  width: auto;
+  margin: 0;
+}
+
+.tracking-settings .hint {
+  margin: 8px 0 4px;
+}
+
 .hint {
   margin: 0;
   font-size: 12px;
diff --git a/shared/popup/popup.html b/shared/popup/popup.html
index 9818ab2..338c304 100644
--- a/shared/popup/popup.html
+++ b/shared/popup/popup.html
@@ -24,6 +24,10 @@
           <span id="pending-label">Pending</span>
           <strong id="pending-count">0</strong>
         </div>
+        <div class="row">
+          <span id="activity-pending-label">Activity batches</span>
+          <strong id="activity-pending-count">0</strong>
+        </div>
         <div class="row url-row">
           <span id="url-label">URL</span>
           <code id="receiver-url"></code>
@@ -55,6 +59,16 @@
         <button id="save-settings" class="secondary">Save</button>
       </section>
 
+      <section class="settings tracking-settings">
+        <label class="tracking-toggle" for="passive-activity-enabled">
+          <input id="passive-activity-enabled" type="checkbox">
+          <span id="passive-activity-label">Track active domain time</span>
+        </label>
+        <p id="passive-activity-disclosure" class="hint">Optional. Collects only the active domain and time spent there. It never sends page URLs, titles, text, keystrokes, or page contents.</p>
+        <label id="passive-activity-exclusions-label" for="passive-activity-exclusions">Excluded domains</label>
+        <textarea id="passive-activity-exclusions" rows="3" spellcheck="false" placeholder="youtube.com"></textarea>
+      </section>
+
       <p id="context-menu-hint" class="hint">Selection and link captures are available from the page context menu.</p>
       <p id="status"></p>
     </main>
diff --git a/shared/popup/popup.js b/shared/popup/popup.js
index 819ac26..8eeff6b 100644
--- a/shared/popup/popup.js
+++ b/shared/popup/popup.js
@@ -11,7 +11,10 @@
   var languageSelectEl = document.getElementById('language-select');
   var fileInputEl = document.getElementById('file-input');
   var pendingCountEl = document.getElementById('pending-count');
+  var pendingActivityCountEl = document.getElementById('activity-pending-count');
   var statusDotEl = document.getElementById('status-dot');
+  var passiveActivityEnabledEl = document.getElementById('passive-activity-enabled');
+  var passiveActivityExclusionsEl = document.getElementById('passive-activity-exclusions');
   var MAX_FILE_TEXT_LENGTH = 2 * 1024 * 1024;
   var MAX_FILE_BYTES = 8 * 1024 * 1024;
   var catalogs = { en: {}, ru: {} };
@@ -23,6 +26,7 @@
     subtitle: 'popup.subtitle',
     'receiver-label': 'label.receiver',
     'pending-label': 'label.pending',
+    'activity-pending-label': 'label.activityPending',
     'url-label': 'label.url',
     'file-label': 'label.file',
     'receiver-url-label': 'label.receiverUrl',
@@ -35,7 +39,10 @@
     'context-menu-hint': 'hint.contextMenu',
     'language-system-option': 'language.system',
     'language-en-option': 'language.en',
-    'language-ru-option': 'language.ru'
+    'language-ru-option': 'language.ru',
+    'passive-activity-label': 'label.passiveActivity',
+    'passive-activity-disclosure': 'hint.passiveActivityDisclosure',
+    'passive-activity-exclusions-label': 'label.passiveActivityExclusions'
   };
 
   function browserLocale() {
@@ -122,9 +129,16 @@
     currentState = state || {};
     var settings = currentState.settings || {};
     pendingCountEl.textContent = String(currentState.pendingCount || 0);
+    pendingActivityCountEl.textContent = String(currentState.pendingActivityCount || 0);
     receiverUrlEl.textContent = settings.receiverUrl || '';
     if (document.activeElement !== receiverInputEl) receiverInputEl.value = settings.receiverUrl || '';
     if (document.activeElement !== receiverTokenInputEl) receiverTokenInputEl.value = settings.receiverToken || '';
+    passiveActivityEnabledEl.checked = settings.passiveActivityEnabled === true;
+    if (document.activeElement !== passiveActivityExclusionsEl) {
+      passiveActivityExclusionsEl.value = Array.isArray(settings.passiveActivityExcludedDomains)
+        ? settings.passiveActivityExcludedDomains.join('\n')
+        : '';
+    }
     applyReceiverState(currentState);
   }
 
@@ -142,7 +156,11 @@
     return {
       receiverUrl: receiverInputEl.value.trim(),
       receiverToken: receiverTokenInputEl.value.trim(),
-      language: currentPreference
+      language: currentPreference,
+      passiveActivityEnabled: passiveActivityEnabledEl.checked === true,
+      passiveActivityExcludedDomains: passiveActivityExclusionsEl.value.split(/[\n,]/).map(function (value) {
+        return value.trim();
+      }).filter(Boolean)
     };
   }
 
diff --git a/shared/protocol.js b/shared/protocol.js
index 7892429..3c5ea9c 100644
--- a/shared/protocol.js
+++ b/shared/protocol.js
@@ -3,6 +3,7 @@
 
   var CAPTURE_SCHEMA_VERSION = 1;
   var DEFAULT_RECEIVER_URL = 'http://127.0.0.1:47731/api/browser-inbox/v1/captures';
+  var DEFAULT_ACTIVITY_URL = 'http://127.0.0.1:47731/api/browser-activity/v1/batches';
   var MAX_FILE_TEXT_LENGTH = 2 * 1024 * 1024;
   var MAX_FILE_BYTES = 8 * 1024 * 1024;
 
@@ -98,6 +99,7 @@
   var api = {
     CAPTURE_SCHEMA_VERSION: CAPTURE_SCHEMA_VERSION,
     DEFAULT_RECEIVER_URL: DEFAULT_RECEIVER_URL,
+    DEFAULT_ACTIVITY_URL: DEFAULT_ACTIVITY_URL,
     MAX_FILE_TEXT_LENGTH: MAX_FILE_TEXT_LENGTH,
     MAX_FILE_BYTES: MAX_FILE_BYTES,
     buildCapture: buildCapture,