Here is a list of all documented variables with links to the class documentation for each member:

- u -

• udp_p2p_ : td::td_api::callProtocol
• udp_reflector_ : td::td_api::callProtocol
• unique_id_ : td::td_api::remoteFile
• unread_count_ : td::td_api::chat, td::td_api::forumTopic, td::td_api::updateChatReadInbox, td::td_api::updateUnreadChatCount, td::td_api::updateUnreadMessageCount
• unread_mention_count_ : td::td_api::chat, td::td_api::forumTopic, td::td_api::updateChatUnreadMentionCount, td::td_api::updateMessageMentionRead
• unread_message_count_ : td::td_api::messageThreadInfo
• unread_reaction_count_ : td::td_api::chat, td::td_api::forumTopic, td::td_api::updateChatUnreadReactionCount, td::td_api::updateMessageUnreadReactions
• unread_reactions_ : td::td_api::message, td::td_api::updateMessageUnreadReactions
• unread_unmuted_count_ : td::td_api::updateUnreadChatCount, td::td_api::updateUnreadMessageCount
• update_order_of_installed_sticker_sets_ : td::td_api::messageSendOptions
• update_recent_reactions_ : td::td_api::addMessageReaction, td::td_api::setStoryReaction
• updates_ : td::td_api::updates
• upgraded_from_basic_group_id_ : td::td_api::supergroupFullInfo
• upgraded_from_max_message_id_ : td::td_api::supergroupFullInfo
• upgraded_to_supergroup_id_ : td::td_api::basicGroup
• uploaded_size_ : td::td_api::remoteFile
• url_ : td::td_api::answerCallbackQuery, td::td_api::authenticationCodeTypeFragment, td::td_api::bankCardActionOpenUrl, td::td_api::botMenuButton, td::td_api::callbackQueryAnswer, td::td_api::getChatBoostLinkInfo, td::td_api::getMessageLinkInfo, td::td_api::getWebAppUrl, td::td_api::getWebPageInstantView, td::td_api::httpUrl, td::td_api::inlineKeyboardButtonTypeLoginUrl, td::td_api::inlineKeyboardButtonTypeUrl, td::td_api::inlineKeyboardButtonTypeWebApp, td::td_api::inlineQueryResultArticle, td::td_api::inlineQueryResultsButtonTypeWebApp, td::td_api::inputInlineQueryResultArticle, td::td_api::internalLinkTypeAttachmentMenuBot, td::td_api::internalLinkTypeChatBoost, td::td_api::internalLinkTypeInstantView, td::td_api::internalLinkTypeMessage, td::td_api::internalLinkTypeSideMenuBot, td::td_api::keyboardButtonTypeWebApp, td::td_api::loginUrlInfoOpen, td::td_api::loginUrlInfoRequestConfirmation, td::td_api::messageSponsorTypeWebsite, td::td_api::openWebApp, td::td_api::pageBlockEmbedded, td::td_api::pageBlockEmbeddedPost, td::td_api::pageBlockPhoto, td::td_api::pageBlockRelatedArticle, td::td_api::paymentOption, td::td_api::paymentProviderOther, td::td_api::richTextAnchorLink, td::td_api::richTextReference, td::td_api::richTextUrl, td::td_api::rtmpUrl, td::td_api::textEntityTypeTextUrl, td::td_api::tMeUrl, td::td_api::userLink, td::td_api::webAppInfo, td::td_api::webPage
• urls_ : td::td_api::tMeUrls
• use_chat_info_database_ : td::td_api::setTdlibParameters
• use_default_disable_mention_notifications_ : td::td_api::chatNotificationSettings
• use_default_disable_pinned_message_notifications_ : td::td_api::chatNotificationSettings
• use_default_mute_for_ : td::td_api::chatNotificationSettings
• use_default_mute_stories_ : td::td_api::chatNotificationSettings, td::td_api::scopeNotificationSettings
• use_default_show_preview_ : td::td_api::chatNotificationSettings
• use_default_show_story_sender_ : td::td_api::chatNotificationSettings
• use_default_sound_ : td::td_api::chatNotificationSettings
• use_default_story_sound_ : td::td_api::chatNotificationSettings
• use_file_database_ : td::td_api::setTdlibParameters
• use_less_data_for_calls_ : td::td_api::autoDownloadSettings
• use_message_database_ : td::td_api::setTdlibParameters
• use_portrait_orientation_ : td::td_api::startGroupCallRecording
• use_secret_chats_ : td::td_api::setTdlibParameters
• use_test_dc_ : td::td_api::setTdlibParameters
• used_sender_id_ : td::td_api::messageReaction
• user_ : td::td_api::updateUser
• user_administrator_rights_ : td::td_api::keyboardButtonTypeRequestChat
• user_chat_id_ : td::td_api::updateNewChatJoinRequest
• user_full_info_ : td::td_api::updateUserFullInfo
• user_id_ : td::td_api::addChatMember, td::td_api::addStickerToSet, td::td_api::botCommandScopeChatMember, td::td_api::call, td::td_api::chatAdministrator, td::td_api::chatBoost, td::td_api::chatEventMemberInvited, td::td_api::chatEventMemberPromoted, td::td_api::chatInviteLinkCount, td::td_api::chatInviteLinkMember, td::td_api::chatJoinRequest, td::td_api::chatStatisticsAdministratorActionsInfo, td::td_api::chatStatisticsInviterInfo, td::td_api::chatStatisticsMessageSenderInfo, td::td_api::chatTypePrivate, td::td_api::chatTypeSecret, td::td_api::contact, td::td_api::createCall, td::td_api::createNewSecretChat, td::td_api::createNewStickerSet, td::td_api::createPrivateChat, td::td_api::gameHighScore, td::td_api::getGameHighScores, td::td_api::getGroupsInCommon, td::td_api::getInlineGameHighScores, td::td_api::getMenuButton, td::td_api::getUser, td::td_api::getUserFullInfo, td::td_api::getUserProfilePhotos, td::td_api::getUserSupportInfo, td::td_api::inlineKeyboardButtonTypeUser, td::td_api::messageChatDeleteMember, td::td_api::messageSenderUser, td::td_api::messageUserShared, td::td_api::messageViewer, td::td_api::processChatJoinRequest, td::td_api::secretChat, td::td_api::setGameScore, td::td_api::setInlineGameScore, td::td_api::setMenuButton, td::td_api::setPassportElementErrors, td::td_api::setStickerSetThumbnail, td::td_api::setUserPersonalProfilePhoto, td::td_api::setUserSupportInfo, td::td_api::sharePhoneNumber, td::td_api::storePaymentPurposeGiftedPremium, td::td_api::storyViewer, td::td_api::suggestUserProfilePhoto, td::td_api::textEntityTypeMentionName, td::td_api::tMeUrlTypeUser, td::td_api::transferChatOwnership, td::td_api::updateUserFullInfo, td::td_api::updateUserStatus, td::td_api::uploadStickerFile
• user_ids_ : td::td_api::addChatMembers, td::td_api::chatJoinRequestsInfo, td::td_api::createNewBasicGroupChat, td::td_api::getChatEventLog, td::td_api::importedContacts, td::td_api::inviteGroupCallParticipants, td::td_api::messageInviteVideoChatParticipants, td::td_api::removeContacts, td::td_api::setCloseFriends, td::td_api::storyPrivacySettingsSelectedUsers, td::td_api::updateAddChatMembersPrivacyForbidden, td::td_api::userPrivacySettingRuleAllowUsers, td::td_api::userPrivacySettingRuleRestrictUsers, td::td_api::users
• user_is_bot_ : td::td_api::keyboardButtonTypeRequestUser
• user_is_premium_ : td::td_api::keyboardButtonTypeRequestUser
• user_location_ : td::td_api::getInlineQueryResults, td::td_api::updateNewChosenInlineResult, td::td_api::updateNewInlineQuery
• username_ : td::td_api::callServerTypeWebrtc, td::td_api::checkChatUsername, td::td_api::pageBlockChatLink, td::td_api::proxyTypeHttp, td::td_api::proxyTypeSocks5, td::td_api::searchPublicChat, td::td_api::setSupergroupUsername, td::td_api::setUsername, td::td_api::toggleBotUsernameIsActive, td::td_api::toggleSupergroupUsernameIsActive, td::td_api::toggleUsernameIsActive
• usernames_ : td::td_api::reorderActiveUsernames, td::td_api::reorderBotActiveUsernames, td::td_api::reorderSupergroupActiveUsernames, td::td_api::supergroup, td::td_api::user
• users_nearby_ : td::td_api::chatsNearby, td::td_api::updateUsersNearby
• utility_bill_ : td::td_api::inputPassportElementUtilityBill, td::td_api::passportElementUtilityBill