diff --git a/README.md b/README.md
index d6f80aa..97a2690 100644
--- a/README.md
+++ b/README.md
@@ -32,6 +32,8 @@ services:
       - /path/to/downloads:/downloads
 ```
 
+To require a password for MeTube, set `METUBE_PASSWORD`, or mount a Docker secret and point `METUBE_PASSWORD_FILE` to it, for example `/run/secrets/metube_password`.
+
 ## ⚙️ Configuration via environment variables
 
 Certain values can be set via environment variables, using the `-e` parameter on the docker command line, or the `environment:` section in docker-compose.
@@ -91,6 +93,9 @@ Certain values can be set via environment variables, using the `-e` parameter on
 * __PGID__: Group under which MeTube will run. Defaults to `1000` (legacy `GID` also supported).
 * __UMASK__: Umask value used by MeTube. Defaults to `022`.
 * __DEFAULT_THEME__: Default theme to use for the UI, can be set to `light`, `dark`, or `auto`. Defaults to `auto`.
+* __METUBE_PASSWORD__: Password required to access MeTube. Leave empty to disable authentication. The password is validated server-side and is never exposed to browser clients. Defaults to empty.
+* __METUBE_PASSWORD_FILE__: Path to a file containing the MeTube password. Useful with Docker secrets. Mutually exclusive with `METUBE_PASSWORD`.
+* __METUBE_SESSION_MAX_AGE__: Session lifetime in seconds for the login cookie. Defaults to `86400` (24 hours). Set to `0` to use a browser-session cookie instead. Logging out always invalidates the current session immediately.
 * __LOGLEVEL__: Log level, can be set to `DEBUG`, `INFO`, `WARNING`, `ERROR`, `CRITICAL`, or `NONE`. Defaults to `INFO`. 
 * __ENABLE_ACCESSLOG__: Whether to enable access log. Defaults to `false`.
 
diff --git a/app/main.py b/app/main.py
index 283de01..771aa31 100644
--- a/app/main.py
+++ b/app/main.py
@@ -4,6 +4,10 @@
 import os
 import sys
 import asyncio
+import secrets
+import time
+from collections.abc import Awaitable, Callable
+from dataclasses import dataclass, field
 from pathlib import Path
 from aiohttp import web
 from aiohttp.log import access_logger
@@ -67,6 +71,9 @@ class Config:
         'HTTPS': 'false',
         'CERTFILE': '',
         'KEYFILE': '',
+        'METUBE_PASSWORD': '',
+        'METUBE_PASSWORD_FILE': '',
+        'METUBE_SESSION_MAX_AGE': '86400',
         'BASE_DIR': '',
         'DEFAULT_THEME': 'auto',
         'MAX_CONCURRENT_DOWNLOADS': '3',
@@ -102,8 +109,20 @@ class Config:
             self.YTDL_OPTIONS_FILE = str(Path(self.YTDL_OPTIONS_FILE).resolve())
         if self.YTDL_OPTIONS_PRESETS_FILE and self.YTDL_OPTIONS_PRESETS_FILE.startswith('.'):
             self.YTDL_OPTIONS_PRESETS_FILE = str(Path(self.YTDL_OPTIONS_PRESETS_FILE).resolve())
+        if self.METUBE_PASSWORD_FILE and self.METUBE_PASSWORD_FILE.startswith('.'):
+            self.METUBE_PASSWORD_FILE = str(Path(self.METUBE_PASSWORD_FILE).resolve())
 
         self._runtime_overrides = {}
+        self.METUBE_PASSWORD = self._load_optional_secret('METUBE_PASSWORD')
+
+        try:
+            self.METUBE_SESSION_MAX_AGE = int(self.METUBE_SESSION_MAX_AGE)
+        except (TypeError, ValueError):
+            log.error('Environment variable "METUBE_SESSION_MAX_AGE" must be an integer')
+            sys.exit(1)
+        if self.METUBE_SESSION_MAX_AGE < 0:
+            log.error('Environment variable "METUBE_SESSION_MAX_AGE" must be zero or greater')
+            sys.exit(1)
 
         success,_ = self.load_ytdl_options()
         if not success:
@@ -123,6 +142,31 @@ class Config:
     def _apply_runtime_overrides(self):
         self.YTDL_OPTIONS.update(self._runtime_overrides)
 
+    def _load_optional_secret(self, key: str) -> str:
+        value = getattr(self, key, '') or ''
+        file_key = f'{key}_FILE'
+        file_value = getattr(self, file_key, '') or ''
+
+        if value and file_value:
+            log.error(f'Only one of "{key}" or "{file_key}" may be set')
+            sys.exit(1)
+
+        if not file_value:
+            return value
+
+        try:
+            with open(file_value, encoding='utf-8') as secret_file:
+                secret = secret_file.read().rstrip('\r\n')
+        except OSError as exc:
+            log.error(f'Could not read "{file_key}" from "{file_value}": {exc}')
+            sys.exit(1)
+
+        if not secret:
+            log.error(f'File "{file_value}" referenced by "{file_key}" is empty')
+            sys.exit(1)
+
+        return secret
+
     # Keys sent to the browser. Sensitive or server-only keys (YTDL_OPTIONS,
     # paths, TLS config, etc.) are intentionally excluded.
     _FRONTEND_KEYS = (
@@ -212,6 +256,167 @@ config = Config()
 # overridden by config file settings or differs from the environment variable.
 logging.getLogger().setLevel(parseLogLevel(str(config.LOGLEVEL)) or logging.INFO)
 
+@dataclass
+class AuthSession:
+    expires_at: float | None
+    socket_ids: set[str] = field(default_factory=set)
+
+
+class AuthManager:
+    COOKIE_NAME = 'metube_session'
+
+    def __init__(self, password: str, *, cookie_path: str, secure_cookie: bool, session_max_age: int):
+        self.password = password
+        self.cookie_path = cookie_path or '/'
+        self.secure_cookie = secure_cookie
+        self.session_max_age = session_max_age
+        self._sessions: dict[str, AuthSession] = {}
+        self._sid_to_session: dict[str, str] = {}
+        self._expiry_tasks: dict[str, asyncio.Task[None]] = {}
+        self._disconnect_socket: Callable[[str], Awaitable[None]] | None = None
+
+    @property
+    def enabled(self) -> bool:
+        return bool(self.password)
+
+    def authenticate(self, password: str) -> bool:
+        return self.enabled and secrets.compare_digest(password, self.password)
+
+    def set_socket_disconnect_callback(self, callback: Callable[[str], Awaitable[None]]) -> None:
+        self._disconnect_socket = callback
+
+    def _expires_at(self) -> float | None:
+        if self.session_max_age <= 0:
+            return None
+        return time.time() + self.session_max_age
+
+    def _is_expired(self, session: AuthSession) -> bool:
+        return session.expires_at is not None and time.time() >= session.expires_at
+
+    def _get_session(self, session_id: str | None) -> AuthSession | None:
+        if not session_id:
+            return None
+        session = self._sessions.get(session_id)
+        if session is None:
+            return None
+        if self._is_expired(session):
+            self.revoke_session(session_id)
+            return None
+        return session
+
+    def _schedule_expiry(self, session_id: str) -> None:
+        if self.session_max_age <= 0:
+            return
+        try:
+            loop = asyncio.get_running_loop()
+        except RuntimeError:
+            return
+        task = self._expiry_tasks.pop(session_id, None)
+        if task is not None:
+            task.cancel()
+        self._expiry_tasks[session_id] = loop.create_task(self._expire_session_after(session_id, self.session_max_age))
+
+    async def _expire_session_after(self, session_id: str, delay: int) -> None:
+        try:
+            await asyncio.sleep(delay)
+        except asyncio.CancelledError:
+            return
+
+        self._expiry_tasks.pop(session_id, None)
+        sids = self.revoke_session(session_id, cancel_expiry=False)
+        if not sids:
+            return
+
+        log.info('Authentication session expired')
+        if self._disconnect_socket is None:
+            return
+        for sid in sids:
+            try:
+                await self._disconnect_socket(sid)
+            except Exception:
+                log.debug('Socket for expired session already disconnected: %s', sid)
+
+    def create_session(self) -> str:
+        session_id = secrets.token_urlsafe(32)
+        self._sessions[session_id] = AuthSession(expires_at=self._expires_at())
+        self._schedule_expiry(session_id)
+        return session_id
+
+    def get_session_id(self, request: web.Request | None) -> str | None:
+        if request is None:
+            return None
+        session_id = request.cookies.get(self.COOKIE_NAME)
+        return session_id if self._get_session(session_id) else None
+
+    def is_authenticated(self, request: web.Request | None) -> bool:
+        return self.get_session_id(request) is not None
+
+    def status_payload(self, request: web.Request | None) -> dict:
+        return {
+            'status': 'ok',
+            'enabled': self.enabled,
+            'authenticated': self.is_authenticated(request),
+        }
+
+    def set_cookie(self, response: web.StreamResponse, session_id: str) -> None:
+        response.set_cookie(
+            self.COOKIE_NAME,
+            session_id,
+            httponly=True,
+            samesite='Lax',
+            secure=self.secure_cookie,
+            path=self.cookie_path,
+            max_age=self.session_max_age if self.session_max_age > 0 else None,
+        )
+
+    def clear_cookie(self, response: web.StreamResponse) -> None:
+        response.del_cookie(
+            self.COOKIE_NAME,
+            httponly=True,
+            samesite='Lax',
+            secure=self.secure_cookie,
+            path=self.cookie_path,
+        )
+
+    def register_socket(self, sid: str, session_id: str | None) -> None:
+        session = self._get_session(session_id)
+        if session is None:
+            return
+        session.socket_ids.add(sid)
+        self._sid_to_session[sid] = session_id
+
+    def unregister_socket(self, sid: str) -> None:
+        session_id = self._sid_to_session.pop(sid, None)
+        if not session_id:
+            return
+        session = self._sessions.get(session_id)
+        if session is None:
+            return
+        session.socket_ids.discard(sid)
+
+    def revoke_session(self, session_id: str, *, cancel_expiry: bool = True) -> list[str]:
+        if cancel_expiry:
+            task = self._expiry_tasks.pop(session_id, None)
+            if task is not None:
+                task.cancel()
+
+        session = self._sessions.pop(session_id, None)
+        if session is None:
+            return []
+
+        sids = list(session.socket_ids)
+        for sid in sids:
+            self._sid_to_session.pop(sid, None)
+        return sids
+
+
+auth_manager = AuthManager(
+    config.METUBE_PASSWORD,
+    cookie_path=(config.URL_PREFIX if config.URL_PREFIX.startswith('/') else f'/{config.URL_PREFIX}'),
+    secure_cookie=config.HTTPS,
+    session_max_age=config.METUBE_SESSION_MAX_AGE,
+)
+
 class ObjectSerializer(json.JSONEncoder):
     def default(self, obj):
         # First try to use __dict__ for custom objects
@@ -228,10 +433,56 @@ class ObjectSerializer(json.JSONEncoder):
         return json.JSONEncoder.default(self, obj)
 
 serializer = ObjectSerializer()
-app = web.Application()
+_PROTECTED_PATHS = {
+    config.URL_PREFIX + 'add',
+    config.URL_PREFIX + 'presets',
+    config.URL_PREFIX + 'cancel-add',
+    config.URL_PREFIX + 'subscribe',
+    config.URL_PREFIX + 'subscriptions',
+    config.URL_PREFIX + 'subscriptions/update',
+    config.URL_PREFIX + 'subscriptions/delete',
+    config.URL_PREFIX + 'subscriptions/check',
+    config.URL_PREFIX + 'delete',
+    config.URL_PREFIX + 'start',
+    config.URL_PREFIX + 'upload-cookies',
+    config.URL_PREFIX + 'delete-cookies',
+    config.URL_PREFIX + 'cookie-status',
+    config.URL_PREFIX + 'history',
+    config.URL_PREFIX + 'version',
+}
+_PROTECTED_PREFIXES = (
+    config.URL_PREFIX + 'download',
+    config.URL_PREFIX + 'audio_download',
+    config.URL_PREFIX + 'socket.io',
+)
+
+
+def _requires_auth_for_path(path: str) -> bool:
+    if path in _PROTECTED_PATHS:
+        return True
+    return any(path.startswith(prefix) for prefix in _PROTECTED_PREFIXES)
+
+
+def _unauthorized_response(request: web.Request | None = None) -> web.Response:
+    response = web.json_response({'status': 'error', 'msg': 'Authentication required'}, status=401)
+    if request is not None and request.cookies.get(auth_manager.COOKIE_NAME):
+        auth_manager.clear_cookie(response)
+    return response
+
+
+@web.middleware
+async def auth_middleware(request: web.Request, handler):
+    if request.method == 'OPTIONS' or not auth_manager.enabled or not _requires_auth_for_path(request.path):
+        return await handler(request)
+    if auth_manager.is_authenticated(request):
+        return await handler(request)
+    return _unauthorized_response(request)
+
+app = web.Application(middlewares=[auth_middleware])
 _cors_origins = [o.strip() for o in config.CORS_ALLOWED_ORIGINS.split(',') if o.strip()] if config.CORS_ALLOWED_ORIGINS else []
 sio = socketio.AsyncServer(cors_allowed_origins=_cors_origins if _cors_origins else [])
 sio.attach(app, socketio_path=config.URL_PREFIX + 'socket.io')
+auth_manager.set_socket_disconnect_callback(sio.disconnect)
 routes = web.RouteTableDef()
 VALID_SUBTITLE_FORMATS = {'srt', 'txt', 'vtt', 'ttml', 'sbv', 'scc', 'dfxp'}
 VALID_SUBTITLE_MODES = {'auto_only', 'manual_only', 'prefer_manual', 'prefer_auto'}
@@ -446,6 +697,21 @@ async def _read_json_request(request: web.Request) -> dict:
     return post
 
 
+async def _disconnect_auth_session(session_id: str) -> None:
+    for sid in auth_manager.revoke_session(session_id):
+        try:
+            await sio.disconnect(sid)
+        except Exception:
+            log.debug('Socket for revoked session already disconnected: %s', sid)
+
+
+def _auth_status_response(request: web.Request) -> web.Response:
+    response = web.json_response(auth_manager.status_payload(request))
+    if request.cookies.get(auth_manager.COOKIE_NAME) and not auth_manager.is_authenticated(request):
+        auth_manager.clear_cookie(response)
+    return response
+
+
 def parse_download_options(post: dict) -> dict:
     """Validate add/subscribe body; raise HTTPBadRequest on invalid input."""
     post = _migrate_legacy_request(dict(post))
@@ -598,6 +864,47 @@ async def add(request):
     return web.Response(text=serializer.encode(status))
 
 
+@routes.get(config.URL_PREFIX + 'auth/status')
+async def auth_status(request):
+    return _auth_status_response(request)
+
+
+@routes.post(config.URL_PREFIX + 'auth/login')
+async def auth_login(request):
+    if not auth_manager.enabled:
+        return _auth_status_response(request)
+
+    post = await _read_json_request(request)
+    password = post.get('password')
+    if password is None:
+        password = ''
+    if not isinstance(password, str):
+        password = str(password)
+
+    if not auth_manager.authenticate(password):
+        log.warning('Rejected UI login with invalid password')
+        return web.json_response(
+            {'status': 'error', 'enabled': True, 'authenticated': False, 'msg': 'Invalid password'},
+            status=401,
+        )
+
+    session_id = auth_manager.create_session()
+    response = web.json_response({'status': 'ok', 'enabled': True, 'authenticated': True})
+    auth_manager.set_cookie(response, session_id)
+    log.info('Authenticated UI session created')
+    return response
+
+
+@routes.post(config.URL_PREFIX + 'auth/logout')
+async def auth_logout(request):
+    session_id = auth_manager.get_session_id(request)
+    if session_id:
+        await _disconnect_auth_session(session_id)
+    response = web.json_response({'status': 'ok', 'enabled': auth_manager.enabled, 'authenticated': False})
+    auth_manager.clear_cookie(response)
+    return response
+
+
 @routes.get(config.URL_PREFIX + 'presets')
 async def presets(request):
     return web.Response(
@@ -789,6 +1096,12 @@ async def history(request):
 
 @sio.event
 async def connect(sid, environ):
+    request = environ.get('aiohttp.request')
+    session_id = auth_manager.get_session_id(request)
+    if auth_manager.enabled and not session_id:
+        log.info('Rejected socket connection for unauthenticated client: %s', sid)
+        raise ConnectionRefusedError('Authentication required')
+    auth_manager.register_socket(sid, session_id)
     log.info(f"Client connected: {sid}")
     await sio.emit('all', serializer.encode(dqueue.get()), to=sid)
     await sio.emit('subscriptions_all', serializer.encode([s.to_public_dict() for s in submgr.list_all()]), to=sid)
@@ -798,6 +1111,12 @@ async def connect(sid, environ):
     if config.YTDL_OPTIONS_FILE:
         await sio.emit('ytdl_options_changed', serializer.encode(get_options_update_time()), to=sid)
 
+
+@sio.event
+async def disconnect(sid):
+    auth_manager.unregister_socket(sid)
+    log.info('Client disconnected: %s', sid)
+
 def get_custom_dirs():
     cache_ttl_seconds = 5
     now = asyncio.get_running_loop().time()
diff --git a/app/tests/test_api.py b/app/tests/test_api.py
index e7fb8ae..5d1d21d 100644
--- a/app/tests/test_api.py
+++ b/app/tests/test_api.py
@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import json
+import time
 from unittest.mock import AsyncMock, MagicMock
 
 import pytest
@@ -30,6 +31,23 @@ def mock_dqueue(monkeypatch):
     return d
 
 
+@pytest.fixture(autouse=True)
+def reset_auth_state(monkeypatch):
+    monkeypatch.setattr(main.auth_manager, "password", "")
+    monkeypatch.setattr(main.auth_manager, "session_max_age", 86400)
+    for task in list(main.auth_manager._expiry_tasks.values()):
+        task.cancel()
+    main.auth_manager._sessions.clear()
+    main.auth_manager._sid_to_session.clear()
+    main.auth_manager._expiry_tasks.clear()
+    yield
+    for task in list(main.auth_manager._expiry_tasks.values()):
+        task.cancel()
+    main.auth_manager._sessions.clear()
+    main.auth_manager._sid_to_session.clear()
+    main.auth_manager._expiry_tasks.clear()
+
+
 def _valid_video_add_body(**kwargs):
     base = {
         "url": "https://example.com/watch?v=1",
@@ -47,6 +65,15 @@ def _valid_video_add_body(**kwargs):
 def _json_request(body: dict | None):
     req = MagicMock(spec=web.Request)
     req.json = AsyncMock(return_value=body)
+    req.cookies = {}
+    req.path = "/"
+    return req
+
+
+def _request_with_cookies(cookies: dict[str, str] | None = None, *, path: str = "/"):
+    req = MagicMock(spec=web.Request)
+    req.cookies = cookies or {}
+    req.path = path
     return req
 
 
@@ -242,6 +269,93 @@ async def test_presets_endpoint_returns_names(mock_dqueue, monkeypatch):
     assert json.loads(resp.text) == {"presets": ["Preset A", "Preset B"]}
 
 
+@pytest.mark.asyncio
+async def test_auth_status_disabled_reports_disabled(mock_dqueue):
+    req = _request_with_cookies()
+    resp = await main.auth_status(req)
+    assert resp.status == 200
+    assert json.loads(resp.text) == {"status": "ok", "enabled": False, "authenticated": False}
+
+
+@pytest.mark.asyncio
+async def test_auth_login_and_logout_roundtrip(mock_dqueue, monkeypatch):
+    monkeypatch.setattr(main.auth_manager, "password", "secret")
+    monkeypatch.setattr(main.auth_manager, "session_max_age", 300)
+
+    login_req = _json_request({"password": "secret"})
+    login_resp = await main.auth_login(login_req)
+    assert login_resp.status == 200
+    login_body = json.loads(login_resp.text)
+    assert login_body == {"status": "ok", "enabled": True, "authenticated": True}
+
+    cookie = login_resp.cookies[main.auth_manager.COOKIE_NAME]
+    session_id = cookie.value
+    assert cookie["max-age"] == "300"
+    status_req = _request_with_cookies({main.auth_manager.COOKIE_NAME: session_id})
+    status_resp = await main.auth_status(status_req)
+    assert json.loads(status_resp.text) == {"status": "ok", "enabled": True, "authenticated": True}
+
+    logout_req = _request_with_cookies({main.auth_manager.COOKIE_NAME: session_id})
+    logout_resp = await main.auth_logout(logout_req)
+    assert logout_resp.status == 200
+    assert json.loads(logout_resp.text) == {"status": "ok", "enabled": True, "authenticated": False}
+    assert session_id not in main.auth_manager._sessions
+
+
+@pytest.mark.asyncio
+async def test_auth_login_rejects_invalid_password(mock_dqueue, monkeypatch):
+    monkeypatch.setattr(main.auth_manager, "password", "secret")
+    req = _json_request({"password": "wrong"})
+    resp = await main.auth_login(req)
+    assert resp.status == 401
+    assert json.loads(resp.text) == {
+        "status": "error",
+        "enabled": True,
+        "authenticated": False,
+        "msg": "Invalid password",
+    }
+
+
+@pytest.mark.asyncio
+async def test_auth_middleware_rejects_protected_requests_without_session(mock_dqueue, monkeypatch):
+    monkeypatch.setattr(main.auth_manager, "password", "secret")
+    req = _request_with_cookies(path=main.config.URL_PREFIX + "history")
+    handler = AsyncMock(return_value=web.Response(text="ok"))
+    resp = await main.auth_middleware(req, handler)
+    assert resp.status == 401
+    handler.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_auth_middleware_rejects_expired_session_and_clears_cookie(mock_dqueue, monkeypatch):
+    monkeypatch.setattr(main.auth_manager, "password", "secret")
+    monkeypatch.setattr(main.auth_manager, "session_max_age", 60)
+
+    session_id = main.auth_manager.create_session()
+    session = main.auth_manager._sessions[session_id]
+    session.expires_at = time.time() - 1
+
+    req = _request_with_cookies(
+        {main.auth_manager.COOKIE_NAME: session_id},
+        path=main.config.URL_PREFIX + "history",
+    )
+    handler = AsyncMock(return_value=web.Response(text="ok"))
+    resp = await main.auth_middleware(req, handler)
+
+    assert resp.status == 401
+    assert resp.cookies[main.auth_manager.COOKIE_NAME]["max-age"] == "0"
+    assert session_id not in main.auth_manager._sessions
+    handler.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_socket_connect_rejects_unauthenticated_client(mock_dqueue, monkeypatch):
+    monkeypatch.setattr(main.auth_manager, "password", "secret")
+    req = _request_with_cookies()
+    with pytest.raises(ConnectionRefusedError):
+        await main.connect("sid-1", {"aiohttp.request": req})
+
+
 @pytest.mark.asyncio
 async def test_cookie_status(mock_dqueue):
     req = MagicMock(spec=web.Request)
diff --git a/app/tests/test_config.py b/app/tests/test_config.py
index 6b096bf..7886d63 100644
--- a/app/tests/test_config.py
+++ b/app/tests/test_config.py
@@ -19,7 +19,7 @@ def _base_env(**overrides: str) -> dict[str, str]:
 
 class ConfigTests(unittest.TestCase):
     def test_url_prefix_gets_trailing_slash(self):
-        with patch.dict(os.environ, _base_env(URL_PREFIX="foo"), clear=False):
+        with patch.dict(os.environ, _base_env(URL_PREFIX="foo"), clear=True):
             c = Config()
         self.assertEqual(c.URL_PREFIX, "foo/")
 
@@ -69,7 +69,7 @@ class ConfigTests(unittest.TestCase):
         with patch.dict(
             os.environ,
             _base_env(YTDL_OPTIONS=json.dumps(opts)),
-            clear=False,
+            clear=True,
         ):
             c = Config()
         self.assertEqual(c.YTDL_OPTIONS["quiet"], True)
@@ -79,36 +79,37 @@ class ConfigTests(unittest.TestCase):
         with patch.dict(
             os.environ,
             _base_env(YTDL_OPTIONS_PRESETS=json.dumps(presets)),
-            clear=False,
+            clear=True,
         ):
             c = Config()
         self.assertEqual(c.YTDL_OPTIONS_PRESETS["Audio extras"]["embed_thumbnail"], True)
 
     def test_invalid_ytdl_options_exits(self):
-        with patch.dict(os.environ, _base_env(YTDL_OPTIONS="not-json"), clear=False):
+        with patch.dict(os.environ, _base_env(YTDL_OPTIONS="not-json"), clear=True):
             with self.assertRaises(SystemExit):
                 Config()
 
     def test_invalid_boolean_env_exits(self):
-        with patch.dict(os.environ, _base_env(CUSTOM_DIRS="maybe"), clear=False):
+        with patch.dict(os.environ, _base_env(CUSTOM_DIRS="maybe"), clear=True):
             with self.assertRaises(SystemExit):
                 Config()
 
     def test_frontend_safe_excludes_secrets(self):
-        with patch.dict(os.environ, _base_env(), clear=False):
+        with patch.dict(os.environ, _base_env(), clear=True):
             c = Config()
         safe = c.frontend_safe()
         self.assertNotIn("YTDL_OPTIONS", safe)
         self.assertNotIn("HOST", safe)
+        self.assertNotIn("METUBE_PASSWORD", safe)
         self.assertEqual(safe["ALLOW_YTDL_OPTIONS_OVERRIDES"], False)
 
     def test_allow_ytdl_options_overrides_boolean_loaded(self):
-        with patch.dict(os.environ, _base_env(ALLOW_YTDL_OPTIONS_OVERRIDES="true"), clear=False):
+        with patch.dict(os.environ, _base_env(ALLOW_YTDL_OPTIONS_OVERRIDES="true"), clear=True):
             c = Config()
         self.assertTrue(c.ALLOW_YTDL_OPTIONS_OVERRIDES)
 
     def test_runtime_override_roundtrip(self):
-        with patch.dict(os.environ, _base_env(), clear=False):
+        with patch.dict(os.environ, _base_env(), clear=True):
             c = Config()
             c.set_runtime_override("cookiefile", "/tmp/c.txt")
             self.assertEqual(c.YTDL_OPTIONS.get("cookiefile"), "/tmp/c.txt")
@@ -123,7 +124,7 @@ class ConfigTests(unittest.TestCase):
             with patch.dict(
                 os.environ,
                 _base_env(YTDL_OPTIONS="{}", YTDL_OPTIONS_FILE=path),
-                clear=False,
+                clear=True,
             ):
                 c = Config()
             self.assertIn("extractor_args", c.YTDL_OPTIONS)
@@ -138,13 +139,50 @@ class ConfigTests(unittest.TestCase):
             with patch.dict(
                 os.environ,
                 _base_env(YTDL_OPTIONS_PRESETS="{}", YTDL_OPTIONS_PRESETS_FILE=path),
-                clear=False,
+                clear=True,
             ):
                 c = Config()
             self.assertIn("With subtitles", c.YTDL_OPTIONS_PRESETS)
         finally:
             os.unlink(path)
 
+    def test_metube_password_loaded_from_env(self):
+        with patch.dict(os.environ, _base_env(METUBE_PASSWORD="secret"), clear=True):
+            c = Config()
+        self.assertEqual(c.METUBE_PASSWORD, "secret")
+
+    def test_metube_password_loaded_from_file(self):
+        with tempfile.NamedTemporaryFile("w", delete=False) as f:
+            f.write("secret\n")
+            path = f.name
+        try:
+            with patch.dict(os.environ, _base_env(METUBE_PASSWORD_FILE=path), clear=True):
+                c = Config()
+            self.assertEqual(c.METUBE_PASSWORD, "secret")
+        finally:
+            os.unlink(path)
+
+    def test_metube_password_and_file_conflict_exits(self):
+        with tempfile.NamedTemporaryFile("w", delete=False) as f:
+            f.write("secret")
+            path = f.name
+        try:
+            with patch.dict(os.environ, _base_env(METUBE_PASSWORD="secret", METUBE_PASSWORD_FILE=path), clear=True):
+                with self.assertRaises(SystemExit):
+                    Config()
+        finally:
+            os.unlink(path)
+
+    def test_metube_session_max_age_loaded(self):
+        with patch.dict(os.environ, _base_env(METUBE_SESSION_MAX_AGE="300"), clear=True):
+            c = Config()
+        self.assertEqual(c.METUBE_SESSION_MAX_AGE, 300)
+
+    def test_invalid_metube_session_max_age_exits(self):
+        with patch.dict(os.environ, _base_env(METUBE_SESSION_MAX_AGE="soon"), clear=True):
+            with self.assertRaises(SystemExit):
+                Config()
+
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/ui/src/app/app.html b/ui/src/app/app.html
index 9ec0472..c214fe7 100644
--- a/ui/src/app/app.html
+++ b/ui/src/app/app.html
@@ -48,7 +48,19 @@
       </ul>
     </div>
     -->
-    <div class="navbar-nav ms-auto">
+    <div class="navbar-nav ms-auto align-items-center gap-2">
+      @if (authEnabled && isAuthenticated) {
+        <button type="button" class="btn btn-outline-light btn-sm"
+          (click)="logout()"
+          [disabled]="logoutInProgress">
+          @if (logoutInProgress) {
+            <span class="spinner-border spinner-border-sm me-2" role="status" aria-hidden="true"></span>
+            Logging out...
+          } @else {
+            Logout
+          }
+        </button>
+      }
       <div class="nav-item dropdown" ngbDropdown placement="bottom-end">
         <button class="btn btn-link nav-link py-2 px-0 px-sm-2 dropdown-toggle d-flex align-items-center"
           id="theme-select"
@@ -83,6 +95,50 @@
   </div>
 </nav>
 
+@if (authStatusLoading) {
+  <div class="auth-modal-backdrop">
+    <section class="auth-modal card shadow-lg" aria-live="polite" aria-busy="true">
+      <div class="card-body p-4 p-md-5 text-center">
+        <div class="spinner-border text-primary mb-3" role="status" aria-hidden="true"></div>
+        <h1 class="h4 mb-2">Loading MeTube</h1>
+        <p class="text-body-secondary mb-0">Checking authentication status...</p>
+      </div>
+    </section>
+  </div>
+} @else if (authEnabled && !isAuthenticated) {
+  <div class="auth-modal-backdrop">
+    <section class="auth-modal card shadow-lg" role="dialog" aria-modal="true" aria-labelledby="auth-modal-title">
+      <div class="card-body p-4 p-md-5">
+        <h1 id="auth-modal-title" class="h3 mb-2">Sign in</h1>
+        <p class="text-body-secondary mb-4">Enter the configured MeTube password to continue.</p>
+        @if (authError) {
+          <div class="alert alert-danger py-2" role="alert">{{authError}}</div>
+        }
+        <form (ngSubmit)="submitLogin()">
+          <div class="mb-3">
+            <label class="form-label" for="login-password">Password</label>
+            <input id="login-password"
+              name="password"
+              type="password"
+              autocomplete="current-password"
+              class="form-control form-control-lg"
+              [(ngModel)]="loginPassword"
+              [disabled]="loginInProgress">
+          </div>
+          <button class="btn btn-primary btn-lg w-100" type="submit"
+            [disabled]="loginInProgress || !loginPassword">
+            @if (loginInProgress) {
+              <span class="spinner-border spinner-border-sm me-2" role="status" aria-hidden="true"></span>
+              Signing in...
+            } @else {
+              Sign in
+            }
+          </button>
+        </form>
+      </div>
+    </section>
+  </div>
+} @else {
 <main role="main" class="container container-xl">
   <form #f="ngForm">
     <div class="container add-url-box">
@@ -952,6 +1008,7 @@
     </table>
   </div>
 </main><!-- /.container -->
+}
 
 <footer class="footer navbar-dark bg-dark py-3 mt-5">
   <div class="container text-center">
diff --git a/ui/src/app/app.sass b/ui/src/app/app.sass
index 7232aaf..93b72a3 100644
--- a/ui/src/app/app.sass
+++ b/ui/src/app/app.sass
@@ -208,3 +208,24 @@ main
 
   &.active
     color: var(--bs-success-text-emphasis)
+
+.auth-modal-backdrop
+  position: fixed
+  inset: 0
+  z-index: 1080
+  display: flex
+  align-items: center
+  justify-content: center
+  padding: 1.5rem
+  background: rgba(15, 23, 42, 0.48)
+  backdrop-filter: blur(10px)
+
+.auth-modal
+  width: min(100%, 28rem)
+  border: 1px solid var(--bs-border-color)
+  border-radius: 1rem
+  box-shadow: 0 1.5rem 3rem rgba(15, 23, 42, 0.24)
+
+@media (max-width: 575.98px)
+  .auth-modal-backdrop
+    padding: 1rem
diff --git a/ui/src/app/app.spec.ts b/ui/src/app/app.spec.ts
index 3b83aeb..588f719 100644
--- a/ui/src/app/app.spec.ts
+++ b/ui/src/app/app.spec.ts
@@ -1,9 +1,10 @@
 import { TestBed } from '@angular/core/testing';
 import { HttpClient } from '@angular/common/http';
-import { Subject, of } from 'rxjs';
+import { BehaviorSubject, Subject, of } from 'rxjs';
 import { App } from './app';
 import { DownloadsService } from './services/downloads.service';
 import { SubscriptionsService } from './services/subscriptions.service';
+import { AuthService, AuthState } from './services/auth.service';
 import { CookieService } from 'ngx-cookie-service';
 
 class DownloadsServiceStub {
@@ -77,6 +78,41 @@ class SubscriptionsServiceStub {
   }
 }
 
+class AuthServiceStub {
+  private stateSubject = new BehaviorSubject<AuthState>({
+    enabled: false,
+    authenticated: false,
+    loading: false,
+  });
+
+  state$ = this.stateSubject.asObservable();
+
+  setState(state: AuthState) {
+    this.stateSubject.next(state);
+  }
+
+  loadStatus() {
+    const state = this.stateSubject.value;
+    return of({ status: 'ok', enabled: state.enabled, authenticated: state.authenticated });
+  }
+
+  login() {
+    this.stateSubject.next({ enabled: true, authenticated: true, loading: false });
+    return of({ status: 'ok', enabled: true, authenticated: true });
+  }
+
+  logout() {
+    const state = this.stateSubject.value;
+    this.stateSubject.next({ ...state, authenticated: false, loading: false });
+    return of({ status: 'ok', enabled: state.enabled, authenticated: false });
+  }
+
+  markUnauthorized() {
+    const state = this.stateSubject.value;
+    this.stateSubject.next({ ...state, authenticated: false, loading: false });
+  }
+}
+
 class CookieServiceStub {
   private cookies = new Map<string, string>();
 
@@ -95,6 +131,7 @@ class CookieServiceStub {
 
 describe('App', () => {
   let downloads: DownloadsServiceStub;
+  let auth: AuthServiceStub;
 
   beforeEach(async () => {
     Object.defineProperty(window, 'matchMedia', {
@@ -110,11 +147,13 @@ describe('App', () => {
       })),
     });
     downloads = new DownloadsServiceStub();
+    auth = new AuthServiceStub();
     await TestBed.configureTestingModule({
       imports: [App],
       providers: [
         { provide: DownloadsService, useValue: downloads },
         { provide: SubscriptionsService, useClass: SubscriptionsServiceStub },
+        { provide: AuthService, useValue: auth },
         { provide: CookieService, useClass: CookieServiceStub },
         {
           provide: HttpClient,
@@ -132,6 +171,17 @@ describe('App', () => {
     expect(app).toBeTruthy();
   });
 
+  it('shows the login form when authentication is enabled and user is signed out', () => {
+    auth.setState({ enabled: true, authenticated: false, loading: false });
+
+    const fixture = TestBed.createComponent(App);
+    fixture.detectChanges();
+
+    const root = fixture.nativeElement as HTMLElement;
+    expect(root.querySelector('#login-password')).not.toBeNull();
+    expect(root.querySelector('button[type="submit"]')?.textContent).toContain('Sign in');
+  });
+
   it('hides manual override input when disabled', () => {
     const fixture = TestBed.createComponent(App);
     fixture.componentInstance.isAdvancedOpen = true;
@@ -175,4 +225,4 @@ describe('App', () => {
 
     expect(payload.ytdlOptionsOverrides).toBe('');
   });
-});
+});
\ No newline at end of file
diff --git a/ui/src/app/app.ts b/ui/src/app/app.ts
index d2a5110..6b8c2be 100644
--- a/ui/src/app/app.ts
+++ b/ui/src/app/app.ts
@@ -12,6 +12,7 @@ import { faGithub } from '@fortawesome/free-brands-svg-icons';
 import { CookieService } from 'ngx-cookie-service';
 import { AddDownloadPayload, DownloadsService } from './services/downloads.service';
 import { SubscriptionsService } from './services/subscriptions.service';
+import { AuthService } from './services/auth.service';
 import { SubscriptionRow } from './interfaces/subscription';
 import { Themes } from './theme';
 import {
@@ -59,6 +60,7 @@ export class App implements AfterViewInit, OnInit, OnDestroy {
   subscriptionsSvc = inject(SubscriptionsService);
   private cookieService = inject(CookieService);
   private http = inject(HttpClient);
+  private authSvc = inject(AuthService);
   private cdr = inject(ChangeDetectorRef);
   private destroyRef = inject(DestroyRef);
 
@@ -109,6 +111,13 @@ export class App implements AfterViewInit, OnInit, OnDestroy {
   ytDlpOptionsUpdateTime: string | null = null;
   ytDlpVersion: string | null = null;
   metubeVersion: string | null = null;
+  authEnabled = false;
+  isAuthenticated = false;
+  authStatusLoading = true;
+  loginPassword = '';
+  loginInProgress = false;
+  logoutInProgress = false;
+  authError: string | null = null;
   isAdvancedOpen = false;
   sortAscending = false;
   expandedErrors: Set<string> = new Set<string>();
@@ -125,6 +134,7 @@ export class App implements AfterViewInit, OnInit, OnDestroy {
   }> = {};
   private readonly selectionCookiePrefix = 'metube_selection_';
   private readonly settingsCookieExpiryDays = 3650;
+  private canAccessApp = false;
   private lastFocusedElement: HTMLElement | null = null;
   private colorSchemeMediaQuery = window.matchMedia('(prefers-color-scheme: dark)');
   private onColorSchemeChanged = () => {
@@ -286,17 +296,42 @@ export class App implements AfterViewInit, OnInit, OnDestroy {
   }
 
   ngOnInit() {
-    this.downloads.getCookieStatus().pipe(takeUntilDestroyed(this.destroyRef)).subscribe(data => {
-      this.hasCookies = !!(data && typeof data === 'object' && 'has_cookies' in data && data.has_cookies);
+    this.authSvc.state$.pipe(takeUntilDestroyed(this.destroyRef)).subscribe((state) => {
+      const canAccessApp = !state.loading && (!state.enabled || state.authenticated);
+      const becameAccessible = canAccessApp && !this.canAccessApp;
+
+      this.authEnabled = state.enabled;
+      this.isAuthenticated = state.authenticated;
+      this.authStatusLoading = state.loading;
+      this.canAccessApp = canAccessApp;
+
+      if (becameAccessible) {
+        this.authError = null;
+        this.loginPassword = '';
+        this.refreshProtectedData();
+      } else if (!canAccessApp) {
+        this.ytDlpVersion = null;
+        this.metubeVersion = null;
+        this.hasCookies = false;
+        this.activeDownloads = 0;
+        this.queuedDownloads = 0;
+        this.completedDownloads = 0;
+        this.failedDownloads = 0;
+        this.totalSpeed = 0;
+        this.hasCompletedDone = false;
+        this.hasFailedDone = false;
+      }
+
       this.cdr.markForCheck();
     });
+
     this.getConfiguration();
     this.getYtdlOptionsUpdateTime();
-    this.getYtdlOptionPresets();
     this.customDirs$ = this.getMatchingCustomDir();
     this.setTheme(this.activeTheme!);
 
     this.colorSchemeMediaQuery.addEventListener('change', this.onColorSchemeChanged);
+    this.authSvc.loadStatus().pipe(takeUntilDestroyed(this.destroyRef)).subscribe();
   }
 
   ngAfterViewInit() {
@@ -311,7 +346,6 @@ export class App implements AfterViewInit, OnInit, OnDestroy {
     });
     // Initialize action button states for already-loaded entries.
     this.updateDoneActionButtons();
-    this.fetchVersionInfo();
   }
 
   ngOnDestroy() {
@@ -319,6 +353,64 @@ export class App implements AfterViewInit, OnInit, OnDestroy {
     this.colorSchemeMediaQuery.removeEventListener('change', this.onColorSchemeChanged);
   }
 
+  submitLogin() {
+    if (this.loginInProgress || !this.authEnabled) {
+      return;
+    }
+    if (!this.loginPassword) {
+      this.authError = 'Please enter the configured password.';
+      return;
+    }
+
+    this.authError = null;
+    this.loginInProgress = true;
+    this.authSvc.login(this.loginPassword)
+      .pipe(
+        takeUntilDestroyed(this.destroyRef),
+        finalize(() => {
+          this.loginInProgress = false;
+          this.cdr.markForCheck();
+        }),
+      )
+      .subscribe((response) => {
+        if (response.status === 'error' || !response.authenticated) {
+          this.authError = this.formatErrorMessage(response.msg || 'Login failed');
+          return;
+        }
+        this.loginPassword = '';
+      });
+  }
+
+  logout() {
+    if (this.logoutInProgress) {
+      return;
+    }
+
+    this.logoutInProgress = true;
+    this.authError = null;
+    this.authSvc.logout()
+      .pipe(
+        takeUntilDestroyed(this.destroyRef),
+        finalize(() => {
+          this.logoutInProgress = false;
+          this.cdr.markForCheck();
+        }),
+      )
+      .subscribe((response) => {
+        if (response.status === 'error') {
+          alert(`Error logging out: ${this.formatErrorMessage(response.msg)}`);
+          return;
+        }
+        this.loginPassword = '';
+      });
+  }
+
+  private refreshProtectedData() {
+    this.refreshCookieStatus();
+    this.getYtdlOptionPresets();
+    this.fetchVersionInfo();
+  }
+
   // workaround to allow fetching of Map values in the order they were inserted
   //  https://github.com/angular/angular/issues/31420
     
@@ -428,9 +520,13 @@ export class App implements AfterViewInit, OnInit, OnDestroy {
   getYtdlOptionPresets() {
     this.downloads.getPresets().pipe(takeUntilDestroyed(this.destroyRef)).subscribe({
       next: (data) => {
-        this.ytdlOptionPresetNames = Array.isArray(data?.presets)
-          ? data.presets.filter((preset): preset is string => typeof preset === 'string')
-          : [];
+        this.ytdlOptionPresetNames =
+          data &&
+          typeof data === 'object' &&
+          'presets' in data &&
+          Array.isArray(data.presets)
+            ? data.presets.filter((preset: unknown): preset is string => typeof preset === 'string')
+            : [];
         if (this.ytdlOptionsPresets?.length) {
           const valid = new Set(this.ytdlOptionPresetNames);
           const filtered = this.ytdlOptionsPresets.filter((p) => valid.has(p));
@@ -1314,7 +1410,10 @@ export class App implements AfterViewInit, OnInit, OnDestroy {
           this.ytDlpVersion = data['yt-dlp'];
           this.metubeVersion = data.version;
         },
-        error: () => {
+        error: (error) => {
+          if (error?.status === 401) {
+            this.authSvc.markUnauthorized();
+          }
           this.ytDlpVersion = null;
           this.metubeVersion = null;
         }
@@ -1452,6 +1551,7 @@ export class App implements AfterViewInit, OnInit, OnDestroy {
   private refreshCookieStatus() {
     this.downloads.getCookieStatus().subscribe(data => {
       this.hasCookies = !!(data && typeof data === 'object' && 'has_cookies' in data && data.has_cookies);
+      this.cdr.markForCheck();
     });
   }
 
diff --git a/ui/src/app/services/auth.service.spec.ts b/ui/src/app/services/auth.service.spec.ts
new file mode 100644
index 0000000..e33746e
--- /dev/null
+++ b/ui/src/app/services/auth.service.spec.ts
@@ -0,0 +1,88 @@
+import { TestBed } from '@angular/core/testing';
+import { provideHttpClient } from '@angular/common/http';
+import { provideHttpClientTesting, HttpTestingController } from '@angular/common/http/testing';
+import { AuthService } from './auth.service';
+import { MeTubeSocket } from './metube-socket.service';
+
+class MeTubeSocketStub {
+  ioSocket = {
+    connected: false,
+    active: false,
+    on: vi.fn(),
+  };
+
+  connect = vi.fn(() => {
+    this.ioSocket.active = true;
+  });
+
+  disconnect = vi.fn(() => {
+    this.ioSocket.active = false;
+    this.ioSocket.connected = false;
+  });
+
+  connectIfNeeded() {
+    if (!this.ioSocket.connected && !this.ioSocket.active) {
+      this.connect();
+    }
+  }
+
+  disconnectIfConnected() {
+    if (this.ioSocket.connected || this.ioSocket.active) {
+      this.disconnect();
+    }
+  }
+}
+
+describe('AuthService', () => {
+  let socket: MeTubeSocketStub;
+  let httpMock: HttpTestingController;
+  let service: AuthService;
+
+  beforeEach(async () => {
+    socket = new MeTubeSocketStub();
+
+    await TestBed.configureTestingModule({
+      providers: [
+        AuthService,
+        provideHttpClient(),
+        provideHttpClientTesting(),
+        { provide: MeTubeSocket, useValue: socket },
+      ],
+    }).compileComponents();
+
+    service = TestBed.inject(AuthService);
+    httpMock = TestBed.inject(HttpTestingController);
+  });
+
+  it('loads auth status and connects the socket for authorized clients', () => {
+    service.loadStatus().subscribe((response) => {
+      expect(response).toEqual({ status: 'ok', enabled: true, authenticated: true });
+    });
+
+    const req = httpMock.expectOne('auth/status');
+    expect(req.request.method).toBe('GET');
+    req.flush({ status: 'ok', enabled: true, authenticated: true });
+
+    expect(socket.connect).toHaveBeenCalled();
+  });
+
+  it('disconnects the socket when markUnauthorized is called', () => {
+    socket.ioSocket.connected = true;
+    service.markUnauthorized();
+    expect(socket.disconnect).toHaveBeenCalled();
+  });
+
+  it('returns a typed error payload on login failure', () => {
+    service.login('bad-password').subscribe((response) => {
+      expect(response.status).toBe('error');
+      expect(response.authenticated).toBe(false);
+      expect(response.msg).toBe('Invalid password');
+    });
+
+    const req = httpMock.expectOne('auth/login');
+    expect(req.request.method).toBe('POST');
+    req.flush({ msg: 'Invalid password' }, { status: 401, statusText: 'Unauthorized' });
+
+    expect(socket.disconnect).toHaveBeenCalled();
+  });
+});
\ No newline at end of file
diff --git a/ui/src/app/services/auth.service.ts b/ui/src/app/services/auth.service.ts
new file mode 100644
index 0000000..e21e3db
--- /dev/null
+++ b/ui/src/app/services/auth.service.ts
@@ -0,0 +1,115 @@
+import { inject, Injectable } from '@angular/core';
+import { HttpClient, HttpErrorResponse } from '@angular/common/http';
+import { BehaviorSubject, Observable, of } from 'rxjs';
+import { catchError, tap } from 'rxjs/operators';
+import { MeTubeSocket } from './metube-socket.service';
+
+export interface AuthResponse {
+  status: string;
+  enabled: boolean;
+  authenticated: boolean;
+  msg?: string;
+}
+
+export interface AuthState {
+  enabled: boolean;
+  authenticated: boolean;
+  loading: boolean;
+}
+
+@Injectable({
+  providedIn: 'root',
+})
+export class AuthService {
+  private http = inject(HttpClient);
+  private socket = inject(MeTubeSocket);
+
+  private stateSubject = new BehaviorSubject<AuthState>({
+    enabled: false,
+    authenticated: false,
+    loading: true,
+  });
+
+  readonly state$ = this.stateSubject.asObservable();
+
+  constructor() {
+    this.socket.ioSocket.on('connect_error', (error: { message?: string }) => {
+      if (error?.message === 'Authentication required') {
+        this.markUnauthorized();
+      }
+    });
+  }
+
+  loadStatus(): Observable<AuthResponse> {
+    return this.http.get<AuthResponse>('auth/status').pipe(
+      tap((response) => this.applyResponse(response)),
+      catchError((error) => of(this.handleError(error))),
+    );
+  }
+
+  login(password: string): Observable<AuthResponse> {
+    return this.http.post<AuthResponse>('auth/login', { password }).pipe(
+      tap((response) => this.applyResponse(response)),
+      catchError((error) => of(this.handleError(error))),
+    );
+  }
+
+  logout(): Observable<AuthResponse> {
+    return this.http.post<AuthResponse>('auth/logout', {}).pipe(
+      tap((response) => this.applyResponse(response)),
+      catchError((error) => of(this.handleError(error, { authenticated: false }))),
+    );
+  }
+
+  markUnauthorized() {
+    const current = this.stateSubject.value;
+    this.stateSubject.next({
+      ...current,
+      authenticated: false,
+      loading: false,
+    });
+    this.socket.disconnectIfConnected();
+  }
+
+  private applyResponse(response: AuthResponse) {
+    this.stateSubject.next({
+      enabled: !!response.enabled,
+      authenticated: !!response.authenticated,
+      loading: false,
+    });
+
+    if (!response.enabled || response.authenticated) {
+      this.socket.connectIfNeeded();
+      return;
+    }
+
+    this.socket.disconnectIfConnected();
+  }
+
+  private handleError(error: HttpErrorResponse, overrides: Partial<AuthState> = {}): AuthResponse {
+    const current = this.stateSubject.value;
+    const enabled = overrides.enabled ?? current.enabled;
+    const authenticated = overrides.authenticated ?? false;
+
+    this.stateSubject.next({
+      enabled,
+      authenticated,
+      loading: false,
+    });
+    this.socket.disconnectIfConnected();
+
+    const msg =
+      error.error instanceof ErrorEvent
+        ? error.error.message
+        : typeof error.error === 'string'
+          ? error.error
+          : error.error?.msg || error.message || 'Request failed';
+
+    return {
+      status: 'error',
+      enabled,
+      authenticated,
+      msg,
+    };
+  }
+}
\ No newline at end of file
diff --git a/ui/src/app/services/downloads.service.spec.ts b/ui/src/app/services/downloads.service.spec.ts
index f07b768..43f2c2b 100644
--- a/ui/src/app/services/downloads.service.spec.ts
+++ b/ui/src/app/services/downloads.service.spec.ts
@@ -4,6 +4,7 @@ import { provideHttpClientTesting, HttpTestingController } from '@angular/common
 import { Subject } from 'rxjs';
 import { DownloadsService, AddDownloadPayload } from './downloads.service';
 import { MeTubeSocket } from './metube-socket.service';
+import { AuthService } from './auth.service';
 import { Download } from '../interfaces';
 
 class MeTubeSocketStub {
@@ -24,6 +25,10 @@ class MeTubeSocketStub {
   }
 }
 
+class AuthServiceStub {
+  markUnauthorized = vi.fn();
+}
+
 function basePayload(): AddDownloadPayload {
   return {
     url: 'https://example.com/v',
@@ -46,17 +51,20 @@ function basePayload(): AddDownloadPayload {
 
 describe('DownloadsService', () => {
   let socket: MeTubeSocketStub;
+  let auth: AuthServiceStub;
   let httpMock: HttpTestingController;
   let service: DownloadsService;
 
   beforeEach(async () => {
     socket = new MeTubeSocketStub();
+    auth = new AuthServiceStub();
     await TestBed.configureTestingModule({
       providers: [
         DownloadsService,
         provideHttpClient(),
         provideHttpClientTesting(),
         { provide: MeTubeSocket, useValue: socket },
+        { provide: AuthService, useValue: auth },
       ],
     }).compileComponents();
 
@@ -88,6 +96,17 @@ describe('DownloadsService', () => {
     req.flush({ status: 'ok' });
   });
 
+  it('marks auth as unauthorized on 401 responses', () => {
+    service.getCookieStatus().subscribe((result) => {
+      expect(result).toEqual({ status: 'error', msg: 'Authentication required' });
+    });
+
+    const req = httpMock.expectOne('cookie-status');
+    req.flush({ msg: 'Authentication required' }, { status: 401, statusText: 'Unauthorized' });
+
+    expect(auth.markUnauthorized).toHaveBeenCalled();
+  });
+
   it('getPresets() fetches configured preset names', () => {
     service.getPresets().subscribe((result) => {
       expect(result).toEqual({ presets: ['Preset A'] });
@@ -275,18 +294,4 @@ describe('DownloadsService', () => {
     socket.emit('cleared', JSON.stringify('u1'));
     expect(service.done.has('u1')).toBe(false);
   });
-
-  it('socket configuration updates configuration', () => {
-    socket.emit('configuration', JSON.stringify({ CUSTOM_DIRS: true }));
-    expect(service.configuration['CUSTOM_DIRS']).toBe(true);
-  });
-
-  it('socket custom_dirs updates customDirs', () => {
-    socket.emit('custom_dirs', JSON.stringify({ download_dir: [''] }));
-    expect(service.customDirs['download_dir']).toEqual(['']);
-  });
-
-  afterEach(() => {
-    httpMock.verify();
-  });
-});
+});
\ No newline at end of file
diff --git a/ui/src/app/services/downloads.service.ts b/ui/src/app/services/downloads.service.ts
index 5a0f1e8..0b13c76 100644
--- a/ui/src/app/services/downloads.service.ts
+++ b/ui/src/app/services/downloads.service.ts
@@ -3,6 +3,7 @@ import { HttpClient, HttpErrorResponse } from '@angular/common/http';
 import { of, Subject } from 'rxjs';
 import { catchError } from 'rxjs/operators';
 import { MeTubeSocket } from './metube-socket.service';
+import { AuthService } from './auth.service';
 import { Download, Status, State } from '../interfaces';
 import { takeUntilDestroyed } from '@angular/core/rxjs-interop';
 
@@ -29,6 +30,7 @@ export interface AddDownloadPayload {
 export class DownloadsService {
   private http = inject(HttpClient);
   private socket = inject(MeTubeSocket);
+  private auth = inject(AuthService);
   loading = true;
   queue = new Map<string, Download>();
   done = new Map<string, Download>();
@@ -99,7 +101,7 @@ export class DownloadsService {
     .pipe(takeUntilDestroyed())
     .subscribe((strdata: string) => {
       const data = JSON.parse(strdata);
-      console.debug("got configuration:", data);
+      console.debug('got configuration:', data);
       this.configuration = data;
       this.configurationChanged.next(data);
     });
@@ -107,7 +109,7 @@ export class DownloadsService {
     .pipe(takeUntilDestroyed())
     .subscribe((strdata: string) => {
       const data = JSON.parse(strdata);
-      console.debug("got custom_dirs:", data);
+      console.debug('got custom_dirs:', data);
       this.customDirs = data;
       this.customDirsChanged.next(data);
     });
@@ -120,6 +122,9 @@ export class DownloadsService {
   }
 
   handleHTTPError(error: HttpErrorResponse) {
+    if (error.status === 401) {
+      this.auth.markUnauthorized();
+    }
     const msg = error.error instanceof ErrorEvent
       ? error.error.message
       : (typeof error.error === 'string'
@@ -146,18 +151,20 @@ export class DownloadsService {
       ytdl_options_presets: payload.ytdlOptionsPresets,
       ytdl_options_overrides: payload.ytdlOptionsOverrides,
     }).pipe(
-      catchError(this.handleHTTPError)
+      catchError(this.handleHTTPError.bind(this))
     );
   }
 
   public getPresets() {
     return this.http.get<{ presets: string[] }>('presets').pipe(
-      catchError(() => of({ presets: [] }))
+      catchError(this.handleHTTPError.bind(this))
     );
   }
 
   public startById(ids: string[]) {
-    return this.http.post('start', {ids: ids});
+    return this.http.post('start', {ids: ids}).pipe(
+      catchError(this.handleHTTPError.bind(this))
+    );
   }
 
   public delById(where: State, ids: string[]) {
@@ -170,7 +177,9 @@ export class DownloadsService {
         }
       }
     }
-    return this.http.post('delete', {where: where, ids: ids});
+    return this.http.post('delete', {where: where, ids: ids}).pipe(
+      catchError(this.handleHTTPError.bind(this))
+    );
   }
 
   public startByFilter(where: State, filter: (dl: Download) => boolean) {
@@ -186,7 +195,7 @@ export class DownloadsService {
   }
   public cancelAdd() {
     return this.http.post<Status>('cancel-add', {}).pipe(
-      catchError(this.handleHTTPError)
+      catchError(this.handleHTTPError.bind(this))
     );
   }
 
@@ -194,19 +203,19 @@ export class DownloadsService {
     const formData = new FormData();
     formData.append('cookies', file);
     return this.http.post<{ status: string; msg?: string }>('upload-cookies', formData).pipe(
-      catchError(this.handleHTTPError)
+      catchError(this.handleHTTPError.bind(this))
     );
   }
 
   deleteCookies() {
     return this.http.post<{ status: string; msg?: string }>('delete-cookies', {}).pipe(
-      catchError(this.handleHTTPError)
+      catchError(this.handleHTTPError.bind(this))
     );
   }
 
   getCookieStatus() {
     return this.http.get<{ status: string; has_cookies: boolean }>('cookie-status').pipe(
-      catchError(this.handleHTTPError)
+      catchError(this.handleHTTPError.bind(this))
     );
   }
-}
+}
\ No newline at end of file
diff --git a/ui/src/app/services/metube-socket.service.ts b/ui/src/app/services/metube-socket.service.ts
index a6c49bf..372be7b 100644
--- a/ui/src/app/services/metube-socket.service.ts
+++ b/ui/src/app/services/metube-socket.service.ts
@@ -12,6 +12,18 @@ export class MeTubeSocket extends Socket {
 
     const path =
       document.location.pathname.replace(/share-target/, '') + 'socket.io';
-    super({ url: '', options: { path } }, appRef);
+    super({ url: '', options: { path, autoConnect: false, withCredentials: true } }, appRef);
   }
-}
+
+  connectIfNeeded() {
+    if (!this.ioSocket.connected && !this.ioSocket.active) {
+      this.connect();
+    }
+  }
+
+  disconnectIfConnected() {
+    if (this.ioSocket.connected || this.ioSocket.active) {
+      this.disconnect();
+    }
+  }
+}
\ No newline at end of file
diff --git a/ui/src/app/services/subscriptions.service.ts b/ui/src/app/services/subscriptions.service.ts
index 2a95fb2..dd861dd 100644
--- a/ui/src/app/services/subscriptions.service.ts
+++ b/ui/src/app/services/subscriptions.service.ts
@@ -4,6 +4,7 @@ import { of, Subject } from 'rxjs';
 import { catchError, tap } from 'rxjs/operators';
 import { takeUntilDestroyed } from '@angular/core/rxjs-interop';
 import { MeTubeSocket } from './metube-socket.service';
+import { AuthService } from './auth.service';
 import { SubscriptionRow } from '../interfaces/subscription';
 import { Status } from '../interfaces';
 import { AddDownloadPayload } from './downloads.service';
@@ -18,6 +19,7 @@ export interface SubscribePayload extends AddDownloadPayload {
 export class SubscriptionsService {
   private http = inject(HttpClient);
   private socket = inject(MeTubeSocket);
+  private auth = inject(AuthService);
   private destroyRef = inject(DestroyRef);
 
   subscriptions = new Map<string, SubscriptionRow>();
@@ -69,6 +71,9 @@ export class SubscriptionsService {
   }
 
   handleHTTPError(error: HttpErrorResponse) {
+    if (error.status === 401) {
+      this.auth.markUnauthorized();
+    }
     const msg =
       error.error instanceof ErrorEvent
         ? error.error.message
@@ -118,7 +123,7 @@ export class SubscriptionsService {
   }
 
   fetchList() {
-    return this.http.get<SubscriptionRow[]>('subscriptions').pipe(catchError(() => of([])));
+    return this.http.get<SubscriptionRow[]>('subscriptions').pipe(catchError((err) => this.handleHTTPError(err)));
   }
 
   refreshList() {
@@ -127,4 +132,4 @@ export class SubscriptionsService {
       catchError((err) => this.handleHTTPError(err)),
     );
   }
-}
+}
\ No newline at end of file