If your talking about going online on a Yu-Gi-Oh! DS game such as "Spirit Caller" or "World Tournament 2007," I suggust going here to get your answer:
http://www.nintendowifi.com/consumerservice/showFAQCategory.do
I hope this help you.
*Using a standard computer with an internet connection, there are a variety of ways to duel other people online using free programs. The best of these in my opinion is YVD 8.6. That stands for Yu-Gi-Oh Virtual Desktop. It lets you use any cards to make any deck and duel other people online. The community is pretty good, and new cards are added withing a month or so of their real life releases. It does take a tiny bit of getting used to, and the new card pictures have to be moved to the correct folder manually, but I find it to be very good. -Dragonheart91*
As of 2014, it is possible for a person to play Duel Masters online. The game is hosted on the website called Kaijudo.
Well speaking as a girl who does play duel monsters I can say yes!^^ There are many girls who watch yugioh, again I should know I met enough of them on youtube. xD I will admit they are hard to find but they do exist! Girls do play duel monsters! (3
Use AR codes to unlock CPU duel in World Championship mode.
no You can create an character without paying and duel 10 duels. Then you have to pay if you want to go on! It's something like this: At the begin, you have 10 duel points or something like that. With one duel point (DP) you can play 1 duel. After your DP are used, you won't be able to duel anymore. You can buy duel points, so you can duel again. You can restart and make new account, then you can duel again 10 duels. But the deck that you get at the begin, totally sucks.
kaijudo portal kaijudo portal
search yugioh online downnload it is not free to play
It doesn't matter the gba and the gbasp can play the same exact games.
duelingnetwork.com you can play other people around the world
KCVDS isn't very good, but you don't need to pay. But yugioh online is one of the greatest duel simulators, but it can be boring at times. It is free to download and play but to duel you will need a DP (Duel Pass), which costs money, but if you don't have any you can watch the other duels. You can download and sign-up for FREE, but Dueling costs real money, and there's no way outta it. I improved the grammar and wording of the original answer, because the meaning was unclear at times. Grammar fixed. Tradecardsonline is not a game site. It has game area but it was made for trading. And there can only be around 10 matches at a time and its hard to get one if u don't pay money. Okay, just so you know, tradecardsonline.com is a game website. That is what it's main focus is. You create a free account. Build a deck, and once you have built it you can go to "play online" and it opens another page where you can play other people if the tables are open.
yugioh network
You could play it on both. Any DS game can play on your DSi
LackeyCCG and Byond (Duel Monsters Genesis).