There are a variety of rule variations available for Blackjack. The different rules shift the odds either in favor of the player, or the house. After the hand has been dealt, players are allowed to double down as the first action of their hand. They can increase the value of their bet up to twice the original, but they only receive one more card, after which they must stand.
Another option that is available at the beginning of a player’s hand is to place an insurance bet. If a dealer has an ace showing the player can place an insurance bet of up to half of their original bet if they believe the dealer has a blackjack (total of 21 in just two cards). If the dealer does have a blackjack this insurance bet is won, usually paid out as 2:1 (saving their original bet if it is lost), if the dealer does not have blackjack the insurance bet is lost and the game proceeds as normal.
Finally, if a player receives two of the same card they can split their hand into two hands. A player proceeds by placing a bet of equal value to the first on the second hand and play the two hands to completion as they would a normal hand. Some casinos place restrictions on splitting aces in that each ace can only receive one card after splitting. Some casinos also allow the option of re-splitting if one of the split cards is again hit with another card of the same value.
The standard rules regarding the dealer can be modified. Modifications include having the dealer hit on a soft 17. A soft 17 is a 17 that includes an Ace as an 11. Games that require dealers to hit on soft 17s raise the odds in the house’s favour.
If the dealer and a player have hands of the same value at the end of play, then it is considered a push and the player’s bet is returned to them. Some casinos differentiate between a blackjack and a 21 acquired through another combination of cards, favoring the blackjack. In some rare cases casinos may not have a push and may instead count a tie as a player loss/house win. This also increases the odds in favour of the house and changes player strategy.