General

Language

• The Language dropdown menu allows you to select the language for the entire BitTorrent Mainline interface. In order for this to work, you must have installed the language pack (utorrent.lng) into BitTorrent Mainline's settings directory, or in the same directory as the BitTorrent Mainline executable itself.
• The More... button opens the download page in your web browser, where you'll find the language pack available for download.

Windows Integration

• The Associate with .torrent files button tells Windows to open .torrent files in BitTorrent Mainline. If maindoc.ico is present in BitTorrent Mainline's settings directory, it will be used as the icon for .torrent files instead of making Windows attempt to generate an icon automatically.
• The Associate with .btsearch files button tells Windows to open .btsearch files in BitTorrent Mainline.
• The Associate with magnet URIs button tells Windows to open magnet URIs with BitTorrent Mainline.
• The Install IPv6/Teredo button makes BitTorrent Mainline install IPv6/Teredo support on the computer. Note that this option works only on operating systems released after Windows XP with at least Service Pack 2 (SP2) installed.
• Check association on startup will tell BitTorrent Mainline to check associations with anything it is associated with each time it is run. If the association no longer belongs to BitTorrent Mainline at start, the user will be prompted for further action.
• Start BitTorrent Mainline on system startup will make BitTorrent Mainline start when Windows starts up.

Privacy

• Check for updates automatically tells BitTorrent Mainline to connect to the BitTorrent Mainline servers to check for newer versions upon startup. Assuming BitTorrent Mainline is open for long enough, it will continue to check for updates periodically, waiting 24 hours between each update check (automatic or manual).
• Update to beta versions tells BitTorrent Mainline to inform the user about beta releases when it checks for updates. Otherwise, the user is only informed of newer stable builds.
• Send anonymous information when checking for updates allows BitTorrent Mainline to send an anonymous, non-private, randomly generated ID and the BitTorrent Mainline version and build numbers to the update server during update checks in order to count the number of people there are using BitTorrent Mainline.
• The Boss-Key field allows you to select a keyboard combination that, when pressed, will toggle the visibility of all traces BitTorrent Mainline on the immediate desktop. The main window and any open dialogs, the taskbar entry, and the system tray icon all disappear when hidden, and appear again when unhidden (by pressing the keyboard combination a second time). To set this field, you must press the keyboard combination you wish to set the boss-key to. To do so, press your choice of modifier keys (any combination of Ctrl, Alt, and Shift) and the key (letters, numbers, function keys, and so on). Make sure the key combination you select is not used by another application, as that can lead to conflicts.
• The Clear Private Data button clears previously used paths in various locations, such as the Add New Torrent dialog and the Create New Torrent dialog.

When Downloading

• Append .!ut to incomplete files tells BitTorrent Mainline to append the .!ut extension to any file in the torrent contents that still hasn't finished downloading. Once a file is completed, the extension gets removed from it. Note that the state of this option takes effect immediately after the preferences are saved, regardless of whether torrent jobs are started, stopped, paused, or queued.
• Pre-allocate all files tells BitTorrent Mainline to create and fully allocate every file you select to download immediately after starting the torrent job. Note that this option does not have an impact on hard drive fragmentation (advantageous or otherwise), as BitTorrent Mainline already allocates each file upon writing to disk even without this option.
• Prevent standby if there are active torrents is self-explanatory; if there are active torrent jobs, BitTorrent Mainline will attempt to keep the computer out of automatic standby mode.