A lot of blackjack players use shuffle tracking in addition to card counting in order to gain an advantage when playing at a brick and mortar casino. Shuffle trackers look for slugs, which are an unshuffled group of cards, tack them throughout the deck, and alter their bets when the dealer gets to those slugs, since they will know what cards are coming.
However, neither card counting nor shuffle tracking works when playing online blackjack. The reason for that is simple: There is no real deck. Sometimes the online blackjack games will show a deck on screen and other times they won’t and you will only see the cards in play. Even if you see a deck on screen, though, it’s impossible to track cards in the deck because the deck you see is only a representation and not a real deck. Also, the cards that are dealt are randomized by a computer program called a random number generator rather than an actual shuffle.
The random number generator can be set different ways. Sometimes it has the effect of shuffling a deck every few hands and sometimes after every hand. Sometimes the online casinos tell you when the deck is being shuffled while other times they don’t. Whatever the case, counting cards and shuffle tracking are impossible when playing online blackjack.
In fact, no strategy that players have devised to gain an advantage at blackjack will work at an online casino. All of the techniques are thwarted by the technology. Instead, the best you can do is play with perfect basic strategy and lower the house edge to 0.5%.