Advanced

Auto-away on Minimize: Switch to away mode whenever the client is minimized (and to back whenever restored).
Automatically Follow Redirects: A connected hub can send out a redirect request, asking your client to disconnect from the current hub and joining another one. Enable this to automatically join that other hub. (You will be disconnected from the current hub no matter what.) If you leave it disabled, you can use the Follow Redirect button to manually follow the redirect.
Clear Search Box After Each Search: After each search, your search terms will be cleared. The last 10 terms will be accessible through the drop-down.
Open the Public Hubs Window at Startup: Opens the Public Hub window at startup, and automatically downloads the configured public hub list.
Open the Download Queue Window at Startup: Shows the Download Queue window at startup.
Open the Favorite Hubs Window at Startup: Shows the Favorite Hubs window at startup.
Open the Finished Downloads Window at Startup: Shows the Finished Downloads window at startup.
Automatically Search for Alternative Download Locations: Every few minutes, the client will search for files in your Download Queue to find more download locations (more users/sources). If the download was started with a TTH root hash available, the autosearch will find exact matches by searching via hash. Otherwise, the autosearch will try to find matches by searching with a slightly modified version of the filename.
Automatically Match Queue for Auto Search Hits: Enable to automatically download a user's list and match them as sources for files in your Download Queue when they've been discovered as a source for one of the files you're downloading. If you download files in sets, that user is probably a source for many more files you're downloading.Enable if unsure. The drawbacks are that it might add slower sources, possibly increasing the time needed to complete a download, and that you'll download a lot of file lists.
Open Private Messages in Their Own Window: If you disable this option, a private message from a user appears as a status line in main chat instead of in a separate window. This could cause you to miss some messages if you don't check the chat regularly. You may not care much for private messages from other users. Ignoring them however, not only lessens the (user-friendly) Direct Connect experience, but is not always wise because failing to reply to a message from an Operator can get you kicked or, in the worst case, permanently banned from that hub.
Ignore Private Messages From Offline Users: Enable this if you wish to ignore private messages from users that are not online on the hub. These messages originate from hub bots and generally contain useful information, like hub specific rules or warnings.
Open Private Messages From Offline Users in Their Own Window: Enable this if you want messages from hub bots in their own window. When disabled they get sent as a status message in main chat instead which is less annoying yet still informative. This option only matters if you're not ignoring private messages from offline users (previous option).
Open New File List Windows in the Background: Keep this disabled if you want newly downloaded filelists to pop up in front of other windows. It can be very annoying to have a new window pop up when you're typing something.
Open New Private Message Windows in the Background: Keep this disabled if you want new private messages filelists to pop up in front of other windows.
Keep Duplicate Files in Your File List: Decides whether to remove duplicate files from your share or to list them but subtract their size from your total reported share size. Duplicate files never count towards your share size, no matter what this is set to.
Register with Windows to Handle dchub:// and adc:// URL Links: When set, DC++ will be the default handler for all dchub:// and adc:// links. These links can appear on web pages, internet shortcuts on your computer, or be typed and run as a program from the Start Menu. Disable this if you prefer for a different application to handle Direct Connect hub links. Disabling will make DC++ remove the keys from the register.
Register with Windows to Handle manget: URI Links: When set, DC++ will register itself to handle magnet: links. These links will let you search the Direct Connect network for a file matching a given file hash, given that the magnet link contains information appropriate for the Direct Connect network. DC++ uses Magnethandler to give a choice between supported P2P applications when magnet.exe is installed on the system or is located in the application's directory. Disabling will make DC++ remove the key from the register.
Use Small Send Buffer: Enable this option if download speeds slow down when uploading files. Users on asynchronous lines with less upstream than downstream will often notice this. Acknowledgement packets for incoming data have to wait in line between the outgoing data. This results in slower sending of acknowledgements packets resulting in a slowdown in the incoming data transfer. Enabling this option will break the outgoing data up into smaller packets so acknowledgement packets can get through more quickly.
Don't Delete File Lists When Exiting: If this option is disabled, DC++ will delete the contents of the FileLists directory, where file lists are stored, when exiting. However, you can open already downloaded filelists instead of downloading them again. These file lists have a chance of being out of date, but for users on slow connections, keeping file lists can save time. Since the file list isn't curent, don't be surprised if the files you enqueue to download have been removed by the user, or moved.
Automatically Disconnect Users Who Leave the Hub: The Direct Connect spirit is all about sharing. You are only sharing when you are connected to one or more hubs. In the past, users of questionable integrity and spirit logged onto a hub, selected a download, and disconnected from the hub again. If everyone did that, there would be nothing to download. Enable this option to avert that kind of behaviour. Note that you might need to disable this option if you're connected to a hub that has a bad connection. The user will regain his/her slot if he/she reconnects within 10 minutes, but you might have opened up another slot for another user in the mean time. This could cause a situation where you have way more upload slots in use than you selected in the settings. Also, if you quit the hub, people downloading from you will not be disconnected.
Show Progress Bars for Transfers: Enable this if you have CPU cycles to spare, and you will get colored progress bars in the Transfer View.
Enable Automatic SFV Checking: Simple File Verification (SFV) is a scheme in which a set of files are accompanied by a so-called sfv-file which contains CRC32 checksums of each file. If there is an sfv-file included, DC++ will check that your download is free of corruption and retry the download that wasn't the case.
Automatically Refresh Share List Every Hour: If you have a dynamic share (files getting added, moved or deleted all the time) enabling this option is a must. Your filelist will be refreshed every hour, keeping the users on the hub up to date with your current share. Disabling this option is really only needed for really large shares where refreshing takes so much time that the client is unusable in the mean time.
Use AntiFragmentation Method for Downloads: This option will try to reserve the full space needed for a file when starting the download. This should reduce the fragmentation of files on your hard drive. (Fragmentation is bad because reading files from your drive will take longer because the drive head has to hop from place to place instead of reading in a continuous fashion.) Enable if unsure. The drawbacks are a short pause at the start of every download during which the drive space is reserved, less drive space being available while you are downloading, and possibly losing progress on your download if Windows crashes and DC++ cannot exit cleanly.
Don't Send the Away Message to Bots: When in away mode, don't send the away message to users that appear to be bots. Having this option disabled is very annoying if you get messages from bots that link chat from multiple users (the most well known example is the Operator Chat facility found in many hubs). Users are judged to be bots if they have an empty Connection type. Enable if unsure.
Skip Zero-Byte Files: When this option is enabled, any zero byte files you try to download will be silently skipped. Sometimes empty files contain information through their naming. However every file, even an empty one, will consume some drive space.
Break on First ADLSearch Match: If you're using the ADLSearch features, keeping this option enabled will make a file show up in only the first search it matches. If disabled, it may appear multiple times, if it matches more than one search.Disable if unsure.
Tab Completion of Nicks in Chat: You can use the tab key to complete partial (beginnings) of nicknames from the main chat text input field (press tab multiple times to switch between multiple nicks). A partial nick will also match if comes after something between brackets (e.g. "arne<tab>" would match "[BBB]arnetheduck").
Enable Safe and Compressed Transfers: When transfering data with a compatible client, DC++ will try to use ZLIB compression with integrity checks. This uses some CPU cycles, but can dramatically speed up transfers of uncompressed files as well as ensure file integrity (reduce the chance of corruption to near zero).Enable if unsure.
Accept Custom User Command From Hub: This option lets you enable or disable DC++'s ability to retrieve custom commands from a remote hub. Custom User Commands may show when you click on the hub's tab, or on a user in the Transfer View, Search Window, or User List, and can enable you to read the rules, perform operator functions, interact with hub bots, etcetera.
Log Filelist transfers: Add successful file lists transfers to your upload and download logs. Otherwise only transferred files are logged. Enabled by default.
Send Unknown /commands to the Hub: Enable this to send /commands that DC++ does not recognize to the hub as normal chat.
Add Finished Files to Share Instantly: If you download files directly to a shared directory, enabling this option will add the files to your share as soon as they're finished. Searches will return the file, and users can download it. It will not appear in your file list until the next refresh.
Use UPnP Control: This option is available on Windows XP and above, with the proper services enabled. It will auto-configure the Windows Firewall and any UPnP (Universal Plug and Play) routers to enable DC++ to operate in active mode without configuring an IP address or port on the Connection settings page. A guide to setting up UPnP can be found here.
Don't download files already in share: This option will stop you from downloading files which already exist in one of your shared directories. Note that this only works with those files which have a TTH.
Use CTRL for line history: Press up arrow while holding down CTRL to scroll through line history. If not enabled, up arrow will be enough.
Open new window when using /join: When using /join >ip<, a new window with the hub will open.
Search for files with TTH root only as standard: Enables "Only results with TTH root" in the search window as standard. This option will cause search results that don't have a TTH to not be displayed.
Advanced resume using TTH: Enables a more advanced form of transfer resuming than the rollback method. The last block of the incomplete file will be checked for validity using the leaves, retrieved from the remote client, of the TTH. If the block fails verification, the previous block in the file will be tried, and so on, until a good block is found, or there is no more data in the file.
Toggle window when selecting an active tab: With this option enabled, clicking on an active tab will mimic the behavior of Windows 98+ and send the currently active window to the background. The most recently accessed window will become the new active window.

Advanced

Boolean Options