The following tables show the blackjack rules offered by some major software providers.
Some software providers allow their licensees to select their own rules.
The rules below for Real Time Gaming used to be standard but with a software update the number of decks may be set by the operator. Comments on Unified Gaming rule variations follow the tables. At Microgaming casinos the player may only double on 9 to 11. This next rule is too involved to explain in the table. In the United States if the dealer has a blackjack the player may lose no more than their original bet.