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 terms will be accessible through the drop-down. You can set how many terms that you want to save by using Search history.
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 Windows registry.
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 Windows registry.
Don't Delete File Lists When Exiting: If this option is disabled, DC++ will delete the contents of the file list directory, where file lists are stored, when exiting. However, you can open already downloaded file lists 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 These file lists have a chance of being out of date, but for users on slow connections, keeping file lists can save time.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.
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.
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.
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.
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 CTRL for line history: Press up arrow while holding down CTRL to scroll through line history. If not enabled, up arrow will be enough.
Don't automatically disconnect favorite users who leave the hub: With this option enabled, and Automatically disconnect users who leave the hub, users who are in your Favorite users page are not disconnected.