In the majority of online blackjack games that a player would encounter will have the dealer standing on all 17 hands, regardless of whether there is an Ace in the hand or not. However there are some online blackjack games and some blackjack variations in which the dealer is allowed to hit on a soft 17.
On the surface, a dealer hitting on a soft 17 does not sound like too bad of a house rule. In theory a dealer who has to hit on a soft 17 because the house rule makes me would be more likely to bust. But that is why it is a theory.
In reality the dealer is actually less likely to bust overall. The reason for this is that Ace. The Ace that is a friend to a blackjack player can also hurt when the dealer can hit on a soft 17. The dealer can reduce an Ace from 11 to 1 just as a blackjack player can. And because of that, the dealer has the chance to rebuild his hand to a stronger one.
For example, if the dealer has an Ace/6 he would have to hit. Let’s say that he hits and gets an 8. The Ace has to be reduced to 1, and he now has a hard 15, which he hits. If he receives anything less than a 7 he is still in the game. And there are more cards less than 7 than there are greater than.
It is because of the dealer’s increased chances of rebuilding his hand to be a stronger one that the house’s rule of a dealer hitting a soft 17 increases the house’s edge by 0.2%. That is a decent sized increase to the house’s edge. Which is why you should avoid any online blackjack games that allow the dealer to hit on a soft 17.