Merge PR #1058: DEFAULT_FOLDER pre-selects a download folder

__is_channel_extraction keyed on id == channel_id. That holds for a channel
tab - /channel/UC..., and the videos, streams, shorts and playlists tabs of a
/@handle URL - but not for a channel addressed on its own: yt-dlp reports the
id in the form the channel was asked for, so a bare handle URL yields '@handle'
and a legacy /c/ URL yields the vanity name.

Neither matched, so both fell through to OUTPUT_TEMPLATE_PLAYLIST and the
folder came out as the feed's title. That is why e2c7778 fixed the reporter's
tab URLs while a bare channel URL - what you get copying the address bar - went
on ignoring OUTPUT_TEMPLATE.

Both forms match uploader_id, which is the handle either way, so compare
against that as well, without case: a legacy vanity name and the handle it
became need not agree on it. A real playlist carries its owner's channel_id and
uploader_id but keeps an id of its own, so it still reads as a playlist; no
playlist id can collide with a handle, since those are 'PL...', 'OLAK...' and
the like.

Verified against the live extractor for all six channel URL forms and a real
playlist.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

README.md

@@ -62,6 +62,7 @@ Certain values can be set via environment variables, using the `-e` parameter on
 * __CUSTOM_DIRS__: Whether to enable downloading videos into custom directories within the __DOWNLOAD_DIR__ (or __AUDIO_DOWNLOAD_DIR__). When enabled, a dropdown appears next to the Add button to specify the download directory. Defaults to `true`.
 * __CREATE_CUSTOM_DIRS__: Whether to support automatically creating directories within the __DOWNLOAD_DIR__ (or __AUDIO_DOWNLOAD_DIR__) if they do not exist. When enabled, the download directory selector supports free-text input, and the specified directory will be created recursively. Defaults to `true`.
 * __CUSTOM_DIRS_EXCLUDE_REGEX__: Regular expression to exclude some custom directories from the dropdown. Empty regex disables exclusion. Defaults to `(^|/)[.@].*$`, which means directories starting with `.` or `@`.
+* __DEFAULT_FOLDER__: Custom directory to pre-select in the download folder field, relative to __DOWNLOAD_DIR__ (or __AUDIO_DOWNLOAD_DIR__), for when most downloads go to the same place. It is only a starting value — the field stays editable, so any other folder can still be picked per download. Requires __CUSTOM_DIRS__; ignored with a warning otherwise. Defaults to empty, i.e. the base download directory.
 * __DOWNLOAD_DIRS_INDEXABLE__: If `true`, the download directories (__DOWNLOAD_DIR__ and __AUDIO_DOWNLOAD_DIR__) are indexable on the web server. Defaults to `false`.
 * __STATE_DIR__: Path to where MeTube will store its persistent state files (`queue.json`, `pending.json`, `completed.json`, `subscriptions.json`). Defaults to `/downloads/.metube` in the Docker image, and `.` otherwise.
 * __TEMP_DIR__: Path where intermediary download files will be saved. Defaults to `/downloads` in the Docker image, and `.` otherwise.
@@ -83,6 +84,8 @@ Certain values can be set via environment variables, using the `-e` parameter on
 * __ALLOW_PRIVATE_ADDRESSES__: Whether to allow downloads from private, loopback, link-local and other non-global addresses. Defaults to `false`, which protects against SSRF by refusing URLs that resolve to internal hosts. Set to `true` only in trusted environments — for example when routing traffic through a proxy/VPN client in Fake-IP mode (sing-box, Clash, Mihomo), which resolves hosts to the `198.18.0.0/15` range. Enabling this disables the SSRF protection entirely, so only use it when you control the network. You do **not** need this to use a proxy on an internal address: a proxy configured through the `proxy` option in `YTDL_OPTIONS` (or the `*_proxy` environment variables) is always reachable at its own host and port, wherever it lives.
 * __YTDL_NIGHTLY_UPDATE_TIME__: If set, will cause MeTube to use [nightly yt-dlp builds](https://github.com/yt-dlp/yt-dlp-nightly-builds) instead of the stable releases. Set to the time (`HH:MM`, 24-hour) when you want the daily upgrades and MeTube restart to happen. Defaults to empty (disabled).
 
+A filename that would exceed the limit the filesystem accepts is shortened to fit, keeping its extension, with room left for the suffixes yt-dlp adds while downloading. Sites that put a long description in the title would otherwise fail the download outright with `File name too long`. Use `trim_file_name` in `YTDL_OPTIONS` if you want names shorter than the filesystem's own limit, or `restrictfilenames` to strip non-ASCII characters.
+
 Enabling `writeinfojson` or `writethumbnail` in `YTDL_OPTIONS` also writes a feed-level `.info.json` and thumbnail when you add a playlist or channel. These reuse the template of the items they belong to — `OUTPUT_TEMPLATE_CHANNEL` or `OUTPUT_TEMPLATE_PLAYLIST` — evaluated against the feed itself, so with the defaults they land in the same folder as the videos, named after the feed. Set `allow_playlist_files` to `false` in `YTDL_OPTIONS` to skip them.
 
 ### 🌐 Web Server & URLs

app/main.py

@@ -62,6 +62,7 @@ class Config:
         'CUSTOM_DIRS': 'true',
         'CREATE_CUSTOM_DIRS': 'true',
         'CUSTOM_DIRS_EXCLUDE_REGEX': r'(^|/)[.@].*$',
+        'DEFAULT_FOLDER': '',
         'DELETE_FILE_ON_TRASHCAN': 'false',
         'STATE_DIR': '.',
         'URL_PREFIX': '',
@@ -127,6 +128,18 @@ class Config:
             if val and not val.endswith('/'):
                 setattr(self, attr, val + '/')
 
+        # DEFAULT_FOLDER only pre-fills the form's folder field, which the UI
+        # does not even show without CUSTOM_DIRS. Sending one anyway would fail
+        # every download on the server's own folder check, so drop it and say so
+        # rather than leaving the user with a form that cannot submit.
+        self.DEFAULT_FOLDER = self.DEFAULT_FOLDER.strip().strip('/')
+        if self.DEFAULT_FOLDER and not self.CUSTOM_DIRS:
+            log.warning(
+                'Ignoring DEFAULT_FOLDER "%s" because CUSTOM_DIRS is not enabled',
+                self.DEFAULT_FOLDER,
+            )
+            self.DEFAULT_FOLDER = ''
+
         # Convert relative addresses to absolute addresses to prevent the failure of file address comparison
         if self.YTDL_OPTIONS_FILE and self.YTDL_OPTIONS_FILE.startswith('.'):
             self.YTDL_OPTIONS_FILE = str(Path(self.YTDL_OPTIONS_FILE).resolve())
@@ -187,6 +200,7 @@ class Config:
     _FRONTEND_KEYS = (
         'CUSTOM_DIRS',
         'CREATE_CUSTOM_DIRS',
+        'DEFAULT_FOLDER',
         'OUTPUT_TEMPLATE_CHAPTER',
         'PUBLIC_HOST_URL',
         'PUBLIC_HOST_AUDIO_URL',

app/tests/test_config.py

@@ -115,6 +115,28 @@ class ConfigTests(unittest.TestCase):
         self.assertNotIn("HOST", safe)
         self.assertEqual(safe["ALLOW_YTDL_OPTIONS_OVERRIDES"], False)
 
+    def test_default_folder_empty_by_default(self):
+        with patch.dict(os.environ, _base_env(), clear=False):
+            c = Config()
+        self.assertEqual(c.DEFAULT_FOLDER, "")
+
+    def test_default_folder_is_trimmed_and_reaches_the_frontend(self):
+        with patch.dict(os.environ, _base_env(DEFAULT_FOLDER=" /youtube/ "), clear=False):
+            c = Config()
+        self.assertEqual(c.DEFAULT_FOLDER, "youtube")
+        self.assertEqual(c.frontend_safe()["DEFAULT_FOLDER"], "youtube")
+
+    def test_default_folder_ignored_without_custom_dirs(self):
+        # The folder field is not shown at all without CUSTOM_DIRS, and sending
+        # a folder anyway is rejected by the download path check.
+        with patch.dict(
+            os.environ,
+            _base_env(DEFAULT_FOLDER="youtube", CUSTOM_DIRS="false"),
+            clear=False,
+        ):
+            c = Config()
+        self.assertEqual(c.DEFAULT_FOLDER, "")
+
     def test_allow_ytdl_options_overrides_boolean_loaded(self):
         with patch.dict(os.environ, _base_env(ALLOW_YTDL_OPTIONS_OVERRIDES="true"), clear=False):
             c = Config()

app/tests/test_download_queue.py

@@ -625,6 +625,82 @@ async def test_playlist_download_not_treated_as_channel(dq_env):
     assert download.output_template.startswith("My Playlist/")
 
 
+def _channel_extraction(entry_id, **extra):
+    """A channel yt-dlp reported as a playlist, addressed by *entry_id*."""
+    return {
+        "_type": "playlist",
+        "id": entry_id,
+        "channel_id": "UCabcd123",
+        "channel": "Odin",
+        "title": "Odin",
+        **extra,
+        "entries": [
+            {
+                "id": "vid1",
+                "title": "Salvia Plath - Pondering",
+                "url": "https://example.com/watch?v=1",
+                "webpage_url": "https://example.com/watch?v=1",
+                "channel": "Odin",
+                "upload_date": "20130804",
+            },
+        ],
+    }
+
+
+async def _add_and_get_template(dq_env, extraction, url):
+    dq_env.OUTPUT_TEMPLATE = "%(channel)s [YT]/%(title)s.%(ext)s"
+    dq_env.OUTPUT_TEMPLATE_CHANNEL = ""
+    dq_env.OUTPUT_TEMPLATE_PLAYLIST = "%(playlist_title)s/%(title)s.%(ext)s"
+
+    def fake_extract(self, _url, *_args, **_kwargs):
+        return extraction
+
+    dq = DownloadQueue(dq_env, AsyncMock())
+    with patch.object(DownloadQueue, "_DownloadQueue__extract_info", fake_extract):
+        result = await dq.add(url, "video", "auto", "any", "best", "", "", 0, auto_start=False)
+    assert result["status"] == "ok"
+    return dq.pending.get("https://example.com/watch?v=1").output_template
+
+
+@pytest.mark.asyncio
+async def test_bare_handle_channel_url_is_treated_as_a_channel(dq_env):
+    """A channel addressed as /@handle reports its id as the handle, not the
+    channel id, and was falling through to OUTPUT_TEMPLATE_PLAYLIST."""
+    template = await _add_and_get_template(
+        dq_env,
+        _channel_extraction("@odin", uploader_id="@odin"),
+        "https://www.youtube.com/@odin",
+    )
+
+    assert template.startswith("Odin [YT]/")
+
+
+@pytest.mark.asyncio
+async def test_legacy_vanity_channel_url_is_treated_as_a_channel(dq_env):
+    """A legacy /c/Name URL reports the vanity name as its id, while
+    uploader_id is still the handle."""
+    template = await _add_and_get_template(
+        dq_env,
+        _channel_extraction("Odin", uploader_id="@odin"),
+        "https://www.youtube.com/c/Odin",
+    )
+
+    assert template.startswith("Odin [YT]/")
+
+
+@pytest.mark.asyncio
+async def test_playlist_with_owner_uploader_id_is_still_a_playlist(dq_env):
+    """A real playlist carries its owner's channel_id and uploader_id, but its
+    own id matches neither, so it must keep the playlist template."""
+    template = await _add_and_get_template(
+        dq_env,
+        _channel_extraction("PLxyz789", uploader_id="@odin", title="My Playlist"),
+        "https://www.youtube.com/playlist?list=PLxyz789",
+    )
+
+    assert template.startswith("My Playlist/")
+
+
 @pytest.mark.asyncio
 async def test_add_merges_global_preset_and_override_options(dq_env):
     notifier = AsyncMock()

app/tests/test_ytdl_utils.py

@@ -50,6 +50,7 @@ class _YoutubeDL:
 
 
 fake_utils.DownloadError = type("DownloadError", (Exception,), {})
+fake_utils.YoutubeDLError = fake_utils.DownloadError
 fake_yt_dlp.YoutubeDL = _YoutubeDL
 fake_impersonate.ImpersonateTarget = _ImpersonateTarget
 fake_networking.impersonate = fake_impersonate
@@ -376,6 +377,49 @@ class ConfinedYoutubeDLTests(unittest.TestCase):
         self.assertEqual(self._prepared_path(""), "")
         self.assertEqual(self._prepared_path("-"), "-")
 
+    def test_overlong_name_is_trimmed_to_fit_the_filesystem(self):
+        # A title long enough to blow the filename limit is what made these
+        # downloads fail outright with [Errno 36] File name too long.
+        long_path = os.path.join(self.base, "a" * 400 + ".mp4")
+
+        result = self._prepared_path(long_path)
+
+        name = os.path.basename(result)
+        self.assertTrue(name.endswith(".mp4"))
+        self.assertLessEqual(len(name.encode("utf-8")), 255 - 32)
+        self.assertEqual(os.path.dirname(result), self.base)
+        # The file must still be writable once yt-dlp adds its own suffixes.
+        self.assertLessEqual(len(f"{name}.f1229065279304024v.part".encode("utf-8")), 255)
+
+    def test_name_within_the_limit_is_left_alone(self):
+        ok = os.path.join(self.base, "Ordinary Title.mp4")
+        self.assertEqual(self._prepared_path(ok), ok)
+
+    def test_limit_counts_bytes_not_characters(self):
+        # 200 CJK characters are 600 bytes: a character count would pass this.
+        long_path = os.path.join(self.base, "音" * 200 + ".mp4")
+
+        name = os.path.basename(self._prepared_path(long_path))
+
+        self.assertLessEqual(len(name.encode("utf-8")), 255 - 32)
+        # A trim landing mid-character must not leave a broken byte sequence.
+        self.assertEqual(name, name.encode("utf-8").decode("utf-8"))
+        self.assertTrue(name.endswith(".mp4"))
+
+    def test_a_long_tail_is_not_mistaken_for_an_extension(self):
+        # os.path.splitext on a title containing a dot late in the string would
+        # otherwise "preserve" a 100-character extension and trim nothing.
+        long_path = os.path.join(self.base, "b" * 300 + "." + "c" * 100)
+
+        name = os.path.basename(self._prepared_path(long_path))
+
+        self.assertLessEqual(len(name.encode("utf-8")), 255 - 32)
+
+    def test_trimming_still_cannot_escape_the_download_directory(self):
+        escaping = os.path.join(self.base, "..", "..", "d" * 400 + ".mp4")
+        with self.assertRaises(ytdl.yt_dlp.utils.DownloadError):
+            self._prepared_path(escaping)
+
 
 class SanitizeEntryForPickleTests(unittest.TestCase):
     def test_nested(self):
@@ -434,6 +478,206 @@ def _make_test_download() -> Download:
     return Download("/tmp", "/tmp", "%(title)s.%(ext)s", "%(title)s.%(ext)s", "best", "any", {}, info)
 
 
+class DownloadLoggerTests(unittest.TestCase):
+    def test_routes_messages_and_retains_only_non_empty_warnings(self):
+        logger = ytdl._DownloadYtdlLogger()
+
+        with self.assertLogs('ytdl', level='DEBUG') as logs:
+            logger.debug('debug detail')
+            logger.warning(' useful warning ')
+            logger.warning('   ')
+            logger.error('error detail')
+
+        self.assertEqual(logger.warnings, ['useful warning'])
+        self.assertIn('DEBUG:ytdl:debug detail', logs.output)
+        self.assertIn('WARNING:ytdl: useful warning ', logs.output)
+        self.assertIn('ERROR:ytdl:error detail', logs.output)
+
+    def test_retains_only_the_last_distinct_warnings(self):
+        logger = ytdl._DownloadYtdlLogger()
+        cap = ytdl._MAX_RETAINED_WARNINGS
+
+        with self.assertLogs('ytdl', level='WARNING') as logs:
+            for index in range(cap + 3):
+                logger.warning(f'fragment {index} not found')
+
+        self.assertEqual(
+            logger.warnings,
+            [f'fragment {index} not found' for index in range(3, cap + 3)],
+        )
+        # Every warning still reaches the log; only the retained list is bounded.
+        self.assertEqual(len(logs.output), cap + 3)
+
+    def test_repeated_warning_is_retained_once(self):
+        logger = ytdl._DownloadYtdlLogger()
+
+        with self.assertLogs('ytdl', level='WARNING'):
+            logger.warning('Requested format is not available')
+            logger.warning('Only images are available for download')
+            logger.warning('Requested format is not available')
+
+        self.assertEqual(
+            logger.warnings,
+            ['Requested format is not available', 'Only images are available for download'],
+        )
+
+    def test_failure_message_puts_the_error_last(self):
+        logger = ytdl._DownloadYtdlLogger()
+
+        with self.assertLogs('ytdl', level='WARNING'):
+            logger.warning('Only images are available for download')
+
+        self.assertEqual(
+            logger.failure_message('ERROR: [youtube] u2HSc2Ym1Vk: No video formats found!'),
+            'Only images are available for download\n'
+            'ERROR: [youtube] u2HSc2Ym1Vk: No video formats found!',
+        )
+
+    def test_failure_message_skips_a_last_warning_that_repeats_the_error(self):
+        logger = ytdl._DownloadYtdlLogger()
+
+        with self.assertLogs('ytdl', level='WARNING'):
+            logger.warning('Video unavailable')
+            # yt-dlp labels errors but hands warnings to the logger unlabelled,
+            # so the same text can arrive through both routes.
+            logger.warning('Requested format is not available')
+
+        self.assertEqual(
+            logger.failure_message('ERROR: Requested format is not available'),
+            'Video unavailable\nERROR: Requested format is not available',
+        )
+
+    def test_failure_message_without_warnings_is_the_error_alone(self):
+        logger = ytdl._DownloadYtdlLogger()
+
+        self.assertEqual(logger.failure_message('ERROR: boom'), 'ERROR: boom')
+
+
+class DownloadResultTests(unittest.TestCase):
+    def _run_download(self, result=0, warnings=(), error=None):
+        download = _make_test_download()
+        statuses = []
+        download.status_queue = types.SimpleNamespace(put=statuses.append)
+        captured_params = {}
+
+        class FakeYoutubeDL:
+            def download(self, urls):
+                self.urls = urls
+                for warning in warnings:
+                    captured_params['logger'].warning(warning)
+                if error is not None:
+                    raise error
+                return result
+
+        def make_youtube_dl(params):
+            captured_params.update(params)
+            return FakeYoutubeDL()
+
+        with patch.object(download, '_make_youtube_dl', side_effect=make_youtube_dl), \
+             patch('ytdl.install_socket_guard'), \
+             patch('ytdl.os.setpgrp'):
+            download._download()
+
+        return statuses, captured_params
+
+    def test_nonzero_result_includes_warning_context_and_forwards_logs(self):
+        warnings = [
+            'The uploader has blocked this video in your country',
+            'No video formats found',
+        ]
+
+        with self.assertLogs('ytdl', level='WARNING') as logs:
+            statuses, params = self._run_download(result=1, warnings=warnings)
+
+        self.assertEqual(
+            statuses[-1],
+            {'status': 'error', 'msg': '\n'.join(warnings)},
+        )
+        self.assertIs(params['logger'].__class__, ytdl._DownloadYtdlLogger)
+        for warning in warnings:
+            self.assertTrue(any(warning in entry for entry in logs.output))
+
+    def test_nonzero_result_without_warning_uses_fallback_message(self):
+        statuses, _ = self._run_download(result=2)
+
+        self.assertEqual(
+            statuses[-1],
+            {'status': 'error', 'msg': 'yt-dlp failed with exit code 2'},
+        )
+
+    def test_warning_does_not_change_success_status(self):
+        statuses, _ = self._run_download(result=0, warnings=['A recoverable warning'])
+
+        self.assertEqual(statuses[-1], {'status': 'finished'})
+
+    def test_youtube_dl_error_carries_the_warnings_that_explain_it(self):
+        # The sequence from issue #1047: yt-dlp raises DownloadError, so the
+        # warnings naming the real cause only reach the user if the exception
+        # branch carries them too.
+        statuses, _ = self._run_download(
+            warnings=[
+                '[youtube] Video unavailable. This video contains content from bryhuangpub,'
+                ' who has blocked it from display on this website or application',
+                'Only images are available for download. use --list-formats to see them',
+                'Requested format is not available',
+            ],
+            error=ytdl.yt_dlp.utils.YoutubeDLError(
+                'ERROR: [youtube] u2HSc2Ym1Vk: No video formats found!'
+            ),
+        )
+
+        self.assertEqual(
+            statuses[-1],
+            {
+                'status': 'error',
+                'msg': '[youtube] Video unavailable. This video contains content from bryhuangpub,'
+                ' who has blocked it from display on this website or application\n'
+                'Only images are available for download. use --list-formats to see them\n'
+                'Requested format is not available\n'
+                'ERROR: [youtube] u2HSc2Ym1Vk: No video formats found!',
+            },
+        )
+
+    def test_youtube_dl_error_drops_a_last_warning_that_repeats_it(self):
+        statuses, _ = self._run_download(
+            warnings=['Earlier warning', 'Requested format is not available'],
+            error=ytdl.yt_dlp.utils.YoutubeDLError('ERROR: Requested format is not available'),
+        )
+
+        self.assertEqual(
+            statuses[-1],
+            {
+                'status': 'error',
+                'msg': 'Earlier warning\nERROR: Requested format is not available',
+            },
+        )
+
+    def test_youtube_dl_error_message_is_bounded(self):
+        cap = ytdl._MAX_RETAINED_WARNINGS
+        statuses, _ = self._run_download(
+            warnings=[f'fragment {index} not found' for index in range(cap + 4)],
+            error=ytdl.yt_dlp.utils.YoutubeDLError('ERROR: giving up'),
+        )
+
+        msg = statuses[-1]['msg']
+        self.assertEqual(
+            msg.split('\n'),
+            [f'fragment {index} not found' for index in range(4, cap + 4)] + ['ERROR: giving up'],
+        )
+
+    def test_nonzero_result_message_is_bounded(self):
+        cap = ytdl._MAX_RETAINED_WARNINGS
+        statuses, _ = self._run_download(
+            result=1,
+            warnings=[f'fragment {index} not found' for index in range(cap + 4)],
+        )
+
+        self.assertEqual(
+            statuses[-1]['msg'].split('\n'),
+            [f'fragment {index} not found' for index in range(4, cap + 4)],
+        )
+
+
 class ProgressThrottleTests(unittest.TestCase):
     def test_downloading_ticks_are_throttled(self):
         dl = _make_test_download()

app/ytdl.py

@@ -32,6 +32,55 @@ from urllib.parse import urlsplit
 
 log = logging.getLogger('ytdl')
 
+
+# Fragmented and live downloads can emit a warning per fragment, and the joined
+# text is persisted with the completed queue and broadcast to every client, so
+# only the last few distinct warnings are kept.
+_MAX_RETAINED_WARNINGS = 5
+
+_REPORT_LABEL_RE = re.compile(r'^(?:ERROR|WARNING):\s*')
+
+
+def _report_body(message):
+    """yt-dlp labels errors with an ``ERROR:`` prefix but hands warnings to the
+    logger unlabelled, so compare the two with any such label removed."""
+    return _REPORT_LABEL_RE.sub('', message).strip()
+
+
+class _DownloadYtdlLogger:
+    """Forward yt-dlp output while retaining warnings for failed downloads."""
+
+    def __init__(self):
+        self._warnings = collections.deque(maxlen=_MAX_RETAINED_WARNINGS)
+
+    @property
+    def warnings(self):
+        return list(self._warnings)
+
+    def debug(self, msg):
+        log.debug('%s', msg)
+
+    def warning(self, msg):
+        log.warning('%s', msg)
+        if msg is not None and (warning := str(msg).strip()) and warning not in self._warnings:
+            self._warnings.append(warning)
+
+    def error(self, msg):
+        log.error('%s', msg)
+
+    def failure_message(self, error_text):
+        """Retained warnings followed by *error_text*, kept last so the actual
+        error stays prominent under the context that explains it."""
+        lines = self.warnings
+        error_text = (error_text or '').strip()
+        if not error_text:
+            return '\n'.join(lines)
+        if lines and _report_body(lines[-1]) == _report_body(error_text):
+            lines.pop()
+        lines.append(error_text)
+        return '\n'.join(lines)
+
+
 # Python 3.14 switches the default multiprocessing start method on Linux
 # (this app's only supported deployment target, per the Dockerfile) from fork
 # to forkserver. Download._download relies on inheriting process state the
@@ -147,6 +196,56 @@ def _sanitize_path_component(value: Any) -> Any:
     return value.lstrip('.').strip() or '_'
 
 
+# Room left for the suffixes yt-dlp appends after prepare_filename has run:
+# '.part' and '.ytdl' while the download is in flight, '.f<format_id>' for a
+# stream fetched on its own before merging, '-Frag<n>' for fragmented
+# downloads. A name trimmed to exactly the limit would still fail the moment
+# one of those is added, which is what the '.part' in the reported errors is.
+_NAME_SUFFIX_RESERVE_BYTES = 32
+# POSIX guarantees at least this much, and it is what ext4/xfs/btrfs allow.
+_FALLBACK_NAME_MAX_BYTES = 255
+# Keep a recognisable stem even on a filesystem with a very short limit.
+_MIN_STEM_BYTES = 16
+# Longer than this is not really an extension (a title ending in '.something'),
+# so the whole name is treated as the stem rather than preserving it.
+_MAX_EXT_BYTES = 16
+
+
+def _name_max_bytes(directory: str) -> int:
+    """The filesystem's filename limit, in bytes, for *directory*."""
+    try:
+        return int(os.pathconf(directory or '.', 'PC_NAME_MAX'))
+    except (OSError, ValueError, AttributeError):
+        # The directory may not exist yet (CREATE_CUSTOM_DIRS makes it during
+        # the download), and pathconf is not available on every platform.
+        return _FALLBACK_NAME_MAX_BYTES
+
+
+def _trim_to_name_max(path: str) -> str:
+    """Shorten the final component of *path* to what the filesystem accepts.
+
+    The limit is a byte count, not a character count: a title of accented or
+    CJK characters hits it in half as many characters, or fewer. The extension
+    is preserved, since it is what decides how the file is handled afterwards.
+    """
+    directory, name = os.path.split(path)
+    if not name:
+        return path
+    encoded = name.encode('utf-8', 'surrogatepass')
+    limit = _name_max_bytes(directory) - _NAME_SUFFIX_RESERVE_BYTES
+    if len(encoded) <= limit:
+        return path
+
+    stem, ext = os.path.splitext(name)
+    ext_bytes = ext.encode('utf-8', 'surrogatepass')
+    if len(ext_bytes) > _MAX_EXT_BYTES:
+        stem, ext, ext_bytes = name, '', b''
+    stem_limit = max(limit - len(ext_bytes), _MIN_STEM_BYTES)
+    # 'ignore' drops a multi-byte character the cut landed inside of.
+    trimmed = stem.encode('utf-8', 'surrogatepass')[:stem_limit].decode('utf-8', 'ignore').rstrip()
+    return os.path.join(directory, (trimmed or '_') + ext)
+
+
 class _ConfinedYoutubeDL(yt_dlp.YoutubeDL):
     """A ``YoutubeDL`` that refuses to emit any output path outside the allowed roots.
 
@@ -170,6 +269,12 @@ class _ConfinedYoutubeDL(yt_dlp.YoutubeDL):
 
     def prepare_filename(self, *args, **kwargs):
         filename = super().prepare_filename(*args, **kwargs)
+        # Titles long enough to exceed the filesystem's filename limit are
+        # common on some sites, and the download fails outright when they do.
+        # Every output path comes through here, so trimming once keeps the
+        # main file, its chapter files, thumbnails and subtitles consistent.
+        if filename and filename != '-':
+            filename = _trim_to_name_max(filename)
         if filename and filename != '-' and self._allowed_roots:
             resolved = os.path.realpath(filename)
             if not any(_is_within_directory(root, resolved) for root in self._allowed_roots):
@@ -664,6 +769,9 @@ class Download:
         # anything else. Skipped when ALLOW_PRIVATE_ADDRESSES trusts the environment.
         install_socket_guard(self.allow_private, proxy_urls=(self.ytdl_opts.get('proxy'),))
         log.info(f"Starting download for: {self.info.title} ({self.info.url})")
+        # Bound outside the try so the except branch can read what was captured
+        # before the error was raised.
+        ytdl_logger = _DownloadYtdlLogger()
         try:
             debug_logging = logging.getLogger().isEnabledFor(logging.DEBUG)
             put_status = self._make_progress_hook()
@@ -710,6 +818,9 @@ class Download:
                 'postprocessor_hooks': [put_status_postprocessor],
                 **self.ytdl_opts,
             }
+            # Set after the ytdl_opts merge: the failure messages below depend on
+            # this logger, so a user-supplied one must not replace it.
+            ytdl_params['logger'] = ytdl_logger
 
             # Add chapter splitting options if enabled
             if self.info.split_by_chapters:
@@ -732,11 +843,15 @@ class Download:
                 )
 
             ret = self._make_youtube_dl(ytdl_params).download([self.info.url])
-            self.status_queue.put({'status': 'finished' if ret == 0 else 'error'})
+            if ret == 0:
+                self.status_queue.put({'status': 'finished'})
+            else:
+                msg = '\n'.join(ytdl_logger.warnings) or f'yt-dlp failed with exit code {ret}'
+                self.status_queue.put({'status': 'error', 'msg': msg})
             log.info(f"Finished download for: {self.info.title}")
         except yt_dlp.utils.YoutubeDLError as exc:
             log.error(f"Download error for {self.info.title}: {str(exc)}")
-            self.status_queue.put({'status': 'error', 'msg': str(exc)})
+            self.status_queue.put({'status': 'error', 'msg': ytdl_logger.failure_message(str(exc))})
 
     async def start(self, notifier, executor=None):
         log.info(f"Preparing download for: {self.info.title}")
@@ -1063,13 +1178,33 @@ class DownloadQueue:
 
     @staticmethod
     def __is_channel_extraction(entry):
-        """Return True when yt-dlp reported a channel tab as a playlist.
+        """Return True when yt-dlp reported a channel as a playlist.
 
-        YouTube channel tabs are extracted with ``_type: 'playlist'`` but set
-        ``id`` equal to ``channel_id``; real playlists keep a distinct id.
+        A channel *tab* -- ``/channel/UC...``, ``/@handle/videos``, and the
+        streams, shorts and playlists tabs -- is extracted with ``id`` equal to
+        ``channel_id``. A channel addressed without a tab keeps the form it was
+        asked for instead: ``@handle`` for a handle URL and the vanity name for
+        a legacy ``/c/`` URL. Both of those match ``uploader_id``, which is the
+        handle either way, so compare against it as well.
+
+        A real playlist has an id of its own and matches neither, even though
+        it also carries its owner's ``channel_id``.
         """
         channel_id = entry.get('channel_id')
-        return bool(channel_id) and entry.get('id') == channel_id
+        entry_id = entry.get('id')
+        if not channel_id or not entry_id:
+            return False
+        if entry_id == channel_id:
+            return True
+        uploader_id = entry.get('uploader_id')
+        if not uploader_id:
+            return False
+        # Compared without case because a legacy vanity name and the handle it
+        # became need not agree on it. No playlist id can collide here: those
+        # are 'PL...', 'OLAK...' and the like, never a handle.
+        handle = uploader_id.casefold()
+        entry_id = entry_id.casefold()
+        return handle in (entry_id, f'@{entry_id}')
 
     async def __import_queue(self):
         for k, v in self.queue.saved_items():

ui/src/app/app.html

@@ -693,6 +693,7 @@
             <app-select-all-checkbox #queueMasterCheckboxRef [id]="'queue'" [list]="downloads.queue" (changed)="queueSelectionChanged($event)" />
           </th>
           <th scope="col">Video</th>
+          <th scope="col" style="width: 7rem;">Format</th>
           <th scope="col" style="width: 8rem;">Speed</th>
           <th scope="col" style="width: 7rem;">ETA</th>
           <th scope="col" style="width: 6rem;"></th>
@@ -726,6 +727,7 @@
                 }
               </div>
             </td>
+            <td class="text-nowrap">{{ formatLabel(download.value) }}</td>
             <td>{{ download.value.speed | speed }}</td>
             <td>{{ download.value.eta | eta }}</td>
             <td>
@@ -757,7 +759,7 @@
       <thead>
         <tr>
           <th scope="col" style="width: 1rem;">
-            <app-select-all-checkbox #doneMasterCheckboxRef [id]="'done'" [list]="downloads.done" (changed)="doneSelectionChanged($event)" />
+            <app-select-all-checkbox #doneMasterCheckboxRef [id]="'done'" [list]="downloads.done" [orderedIds]="cachedSortedDoneIds" (changed)="doneSelectionChanged($event)" />
           </th>
           <th scope="col">Video</th>
           <th scope="col">Type</th>

ui/src/app/app.spec.ts

@@ -6,6 +6,7 @@ import { DownloadsService } from './services/downloads.service';
 import { SubscriptionsService } from './services/subscriptions.service';
 import { ToastService } from './services/toast.service';
 import { CookieService } from 'ngx-cookie-service';
+import { Download } from './interfaces';
 
 class DownloadsServiceStub {
   loading = false;
@@ -148,6 +149,25 @@ describe('App', () => {
     expect(app).toBeTruthy();
   });
 
+  it('pre-fills the download folder from DEFAULT_FOLDER', () => {
+    const fixture = TestBed.createComponent(App);
+    fixture.detectChanges();
+
+    downloads.configurationChanged.next({ DEFAULT_FOLDER: 'youtube' });
+
+    expect(fixture.componentInstance.folder).toBe('youtube');
+  });
+
+  it('does not overwrite a folder the user already typed', () => {
+    const fixture = TestBed.createComponent(App);
+    fixture.detectChanges();
+    fixture.componentInstance.folder = 'music';
+
+    downloads.configurationChanged.next({ DEFAULT_FOLDER: 'youtube' });
+
+    expect(fixture.componentInstance.folder).toBe('music');
+  });
+
   it('asIsOrder returns a stable comparator value (insertion order preserved)', () => {
     const fixture = TestBed.createComponent(App);
     const app = fixture.componentInstance;
@@ -229,6 +249,46 @@ describe('App', () => {
     expect(root.textContent).toContain('starts in');
   });
 
+  it('shows the queued format in the Downloading table', () => {
+    downloads.queue.set('https://example.com/v', {
+      id: 'v1',
+      title: 'Some Video',
+      url: 'https://example.com/v',
+      download_type: 'audio',
+      quality: 'best',
+      format: 'flac',
+      folder: '',
+      custom_name_prefix: '',
+      playlist_item_limit: 0,
+      status: 'downloading',
+      msg: '',
+      percent: 10,
+      speed: 0,
+      eta: 0,
+      filename: '',
+      checked: false,
+    });
+    downloads.queueChanged.next();
+
+    const fixture = TestBed.createComponent(App);
+    fixture.detectChanges();
+
+    const row = (fixture.nativeElement as HTMLElement).querySelector('tbody tr');
+    expect(row?.textContent).toContain('FLAC');
+  });
+
+  it('labels formats the way the form does, and copes with an unknown one', () => {
+    const app = TestBed.createComponent(App).componentInstance;
+    const base = { format: '' } as Download;
+
+    expect(app.formatLabel({ ...base, format: 'any' })).toBe('Auto');
+    expect(app.formatLabel({ ...base, format: 'mp4' })).toBe('MP4');
+    expect(app.formatLabel({ ...base, format: 'srt' })).toBe('SRT');
+    // A format from a record older than the option list still reads sensibly.
+    expect(app.formatLabel({ ...base, format: 'mkv' })).toBe('MKV');
+    expect(app.formatLabel(base)).toBe('-');
+  });
+
   it('includes titleRegex in subscribe payload', () => {
     const fixture = TestBed.createComponent(App);
     const app = fixture.componentInstance;

ui/src/app/app.ts

@@ -137,6 +137,9 @@ export class App implements AfterViewInit, OnInit, OnDestroy {
   sortAscending = false;
   expandedErrors: Set<string> = new Set<string>();
   cachedSortedDone: [string, Download][] = [];
+  // The done ids in rendered order, so a shift-click range follows the sort
+  // the user is looking at rather than the map's insertion order.
+  cachedSortedDoneIds: string[] = [];
   lastCopiedErrorId: string | null = null;
   private previousDownloadType = 'video';
   private addRequestSub?: Subscription;
@@ -434,6 +437,12 @@ export class App implements AfterViewInit, OnInit, OnDestroy {
         if (!Number.isNaN(playlistItemLimit) && playlistItemLimit > 0) {
           this.playlistItemLimit = playlistItemLimit;
         }
+        // Pre-fill the download folder, unless the user has already typed one
+        // this session. The server drops DEFAULT_FOLDER when CUSTOM_DIRS is
+        // off, so there is nothing to guard against here.
+        if (!this.folder) {
+          this.folder = String(config['DEFAULT_FOLDER'] ?? '');
+        }
         // Set chapter template from backend config if not already set by cookie
         if (!this.chapterTemplate) {
           this.chapterTemplate = config['OUTPUT_TEMPLATE_CHAPTER'];
@@ -909,6 +918,22 @@ export class App implements AfterViewInit, OnInit, OnDestroy {
     return type.charAt(0).toUpperCase() + type.slice(1);
   }
 
+  // The format the download was queued with, labelled the way the form labels
+  // it, so a queued item can be told apart while it is still downloading.
+  formatLabel(download: Download): string {
+    const format = (download.format || '').trim();
+    if (!format) {
+      return '-';
+    }
+    const options: Option[] = [
+      ...this.videoFormats,
+      ...this.audioFormats,
+      ...this.captionFormats,
+      ...this.thumbnailFormats,
+    ];
+    return options.find(o => o.id === format)?.text ?? format.toUpperCase();
+  }
+
   formatCodecLabel(download: Download): string {
     if (download.download_type !== 'video') {
       const format = (download.format || '').toUpperCase();
@@ -1532,6 +1557,7 @@ export class App implements AfterViewInit, OnInit, OnDestroy {
       result.reverse();
     }
     this.cachedSortedDone = result;
+    this.cachedSortedDoneIds = result.map(([key]) => key);
   }
 
   toggleErrorDetail(id: string) {

ui/src/app/components/master-checkbox.component.spec.ts

@@ -2,6 +2,38 @@ import { TestBed } from '@angular/core/testing';
 import { SelectAllCheckboxComponent } from './master-checkbox.component';
 import { Checkable } from '../interfaces';
 
+function makeList(ids: string[]): Map<string, Checkable> {
+  const list = new Map<string, Checkable>();
+  for (const id of ids) {
+    list.set(id, { checked: false });
+  }
+  return list;
+}
+
+function makeMaster(list: Map<string, Checkable>, orderedIds: string[] | null = null) {
+  const fixture = TestBed.createComponent(SelectAllCheckboxComponent);
+  fixture.componentRef.setInput('id', 'queue');
+  fixture.componentRef.setInput('list', list);
+  if (orderedIds) {
+    fixture.componentRef.setInput('orderedIds', orderedIds);
+  }
+  fixture.detectChanges();
+  return fixture;
+}
+
+// Simulates what the item checkbox does: ngModel writes the new state, then
+// the change handler reports the click to the master.
+function clickItem(
+  master: SelectAllCheckboxComponent,
+  list: Map<string, Checkable>,
+  id: string,
+  shift = false,
+) {
+  const item = list.get(id)!;
+  item.checked = !item.checked;
+  master.selectionChanged(id, shift);
+}
+
 describe('SelectAllCheckboxComponent', () => {
   beforeEach(async () => {
     await TestBed.configureTestingModule({
@@ -20,4 +52,87 @@ describe('SelectAllCheckboxComponent', () => {
     fixture.componentInstance.clicked();
     expect(list.get('u1')?.checked).toBe(true);
   });
+
+  it('shift-click checks every item between the two clicks', () => {
+    const list = makeList(['u1', 'u2', 'u3', 'u4', 'u5']);
+    const master = makeMaster(list).componentInstance;
+
+    clickItem(master, list, 'u2');
+    clickItem(master, list, 'u4', true);
+
+    expect([...list.values()].map((i) => i.checked)).toEqual([false, true, true, true, false]);
+  });
+
+  it('extends upwards as well as downwards', () => {
+    const list = makeList(['u1', 'u2', 'u3', 'u4']);
+    const master = makeMaster(list).componentInstance;
+
+    clickItem(master, list, 'u4');
+    clickItem(master, list, 'u2', true);
+
+    expect([...list.values()].map((i) => i.checked)).toEqual([false, true, true, true]);
+  });
+
+  it('shift-clicking a checked box clears the range', () => {
+    const list = makeList(['u1', 'u2', 'u3']);
+    list.forEach((item) => (item.checked = true));
+    const master = makeMaster(list).componentInstance;
+
+    clickItem(master, list, 'u1');
+    clickItem(master, list, 'u3', true);
+
+    expect([...list.values()].map((i) => i.checked)).toEqual([false, false, false]);
+  });
+
+  it('follows the rendered order, not the map order', () => {
+    // The done list renders newest-first, so its rendered order is not the
+    // order the entries sit in the map. u2 lies inside the range on screen
+    // and outside it in the map, which is what separates the two.
+    const list = makeList(['u1', 'u2', 'u3', 'u4']);
+    const master = makeMaster(list, ['u4', 'u2', 'u3', 'u1']).componentInstance;
+
+    clickItem(master, list, 'u4');
+    clickItem(master, list, 'u3', true);
+
+    // u1 (rendered last) stays clear; u2 is swept up with the range.
+    expect([...list.values()].map((i) => i.checked)).toEqual([false, true, true, true]);
+  });
+
+  it('a plain click after a range starts a new anchor', () => {
+    const list = makeList(['u1', 'u2', 'u3', 'u4']);
+    const master = makeMaster(list).componentInstance;
+
+    clickItem(master, list, 'u1');
+    clickItem(master, list, 'u2', true);
+    clickItem(master, list, 'u4');
+
+    expect([...list.values()].map((i) => i.checked)).toEqual([true, true, false, true]);
+  });
+
+  it('select-all clears the anchor so the next shift-click is a plain toggle', () => {
+    const list = makeList(['u1', 'u2', 'u3']);
+    const fixture = makeMaster(list);
+    const master = fixture.componentInstance;
+
+    clickItem(master, list, 'u1');
+    master.selected = true;
+    master.clicked();
+    master.selected = false;
+    master.clicked();
+    clickItem(master, list, 'u3', true);
+
+    expect([...list.values()].map((i) => i.checked)).toEqual([false, false, true]);
+  });
+
+  it('ignores a range whose anchor row is gone', () => {
+    const list = makeList(['u1', 'u2', 'u3']);
+    const master = makeMaster(list).componentInstance;
+
+    clickItem(master, list, 'u1');
+    // The anchor finishes downloading and leaves the queue.
+    list.delete('u1');
+    clickItem(master, list, 'u3', true);
+
+    expect([...list.values()].map((i) => i.checked)).toEqual([false, true]);
+  });
 });

ui/src/app/components/master-checkbox.component.ts

@@ -20,17 +20,33 @@ import { FormsModule } from "@angular/forms";
 export class SelectAllCheckboxComponent {
   readonly id = input.required<string>();
   readonly list = input.required<Map<string, Checkable>>();
+  // The ids in the order the rows are rendered. The done list is sorted for
+  // display, so its order is not the map's insertion order, and a range
+  // selection has to follow what the user sees. Left unset, the map order is
+  // the rendered order.
+  readonly orderedIds = input<string[] | null>(null);
   readonly changed = output<number>();
 
   readonly masterCheckbox = viewChild.required<ElementRef>('masterCheckbox');
   selected!: boolean;
 
+  // The item a range extends from: the last one toggled on its own.
+  private anchorId: string | null = null;
+
   clicked() {
     this.list().forEach(item => item.checked = this.selected);
+    // Select-all is not a position, so there is nothing to extend from next.
+    this.anchorId = null;
     this.selectionChanged();
   }
 
-  selectionChanged() {
+  selectionChanged(id?: string, extend = false) {
+    if (id !== undefined) {
+      if (extend && this.anchorId !== null && this.anchorId !== id) {
+        this.applyRange(this.anchorId, id);
+      }
+      this.anchorId = id;
+    }
     const masterCheckbox = this.masterCheckbox();
     if (!masterCheckbox)
       return;
@@ -40,4 +56,27 @@ export class SelectAllCheckboxComponent {
     masterCheckbox.nativeElement.indeterminate = checked > 0 && checked < this.list().size;
     this.changed.emit(checked);
   }
+
+  // Everything between the anchor and the just-clicked row takes the state the
+  // click produced, so shift-clicking a checked box clears the range and
+  // shift-clicking an unchecked one fills it.
+  private applyRange(fromId: string, toId: string) {
+    const ids = this.orderedIds() ?? Array.from(this.list().keys());
+    const from = ids.indexOf(fromId);
+    const to = ids.indexOf(toId);
+    // A row can disappear between two clicks (a download finishing moves it
+    // from the queue to the done list); without both ends there is no range.
+    if (from < 0 || to < 0) {
+      return;
+    }
+    const target = this.list().get(toId)?.checked ?? false;
+    const start = Math.min(from, to);
+    const end = Math.max(from, to);
+    for (let i = start; i <= end; i++) {
+      const item = this.list().get(ids[i]);
+      if (item) {
+        item.checked = target;
+      }
+    }
+  }
 }

ui/src/app/components/slave-checkbox.component.spec.ts

@@ -22,4 +22,33 @@ describe('ItemCheckboxComponent', () => {
     itemFixture.detectChanges();
     expect(itemFixture.componentInstance).toBeTruthy();
   });
+
+  it('reports the shift modifier from the click to the master', () => {
+    const masterFixture = TestBed.createComponent(SelectAllCheckboxComponent);
+    masterFixture.componentRef.setInput('id', 'q');
+    masterFixture.componentRef.setInput('list', new Map());
+    masterFixture.detectChanges();
+    const master = masterFixture.componentInstance;
+    const reported: [string | undefined, boolean | undefined][] = [];
+    master.selectionChanged = (id?: string, extend?: boolean) => {
+      reported.push([id, extend]);
+    };
+
+    const itemFixture = TestBed.createComponent(ItemCheckboxComponent);
+    itemFixture.componentRef.setInput('id', 'row1');
+    itemFixture.componentRef.setInput('master', master);
+    itemFixture.componentRef.setInput('checkable', { checked: false });
+    itemFixture.detectChanges();
+    const item = itemFixture.componentInstance;
+
+    item.clicked(new MouseEvent('click', { shiftKey: true }));
+    item.changed();
+    // The modifier must not stick to the next toggle.
+    item.changed();
+
+    expect(reported).toEqual([
+      ['row1', true],
+      ['row1', false],
+    ]);
+  });
 });

ui/src/app/components/slave-checkbox.component.ts

@@ -7,7 +7,7 @@ import { FormsModule } from '@angular/forms';
     selector: 'app-item-checkbox',
     template: `
   <div class="form-check">
-    <input type="checkbox" class="form-check-input" id="{{master().id()}}-{{id()}}-select" [(ngModel)]="checkable().checked" (change)="master().selectionChanged()" [attr.aria-label]="'Select item ' + id()">
+    <input type="checkbox" class="form-check-input" id="{{master().id()}}-{{id()}}-select" [(ngModel)]="checkable().checked" (click)="clicked($event)" (change)="changed()" [attr.aria-label]="'Select item ' + id()">
     <label class="form-check-label visually-hidden" for="{{master().id()}}-{{id()}}-select">Select item</label>
   </div>
 `,
@@ -22,4 +22,19 @@ export class ItemCheckboxComponent {
   readonly id = input.required<string>();
   readonly master = input.required<SelectAllCheckboxComponent>();
   readonly checkable = input.required<Checkable>();
+
+  // click fires before change, so the modifier is recorded here and read once
+  // ngModel has written the new state into the checkable. Keyboard activation
+  // fires change without a click, which is a plain toggle.
+  private extend = false;
+
+  clicked(event: MouseEvent) {
+    this.extend = event.shiftKey;
+  }
+
+  changed() {
+    const extend = this.extend;
+    this.extend = false;
+    this.master().selectionChanged(this.id(), extend);
+  }
 }