Betfair isn't purely a no deposit bonus casino, but from time to time you may find free spins no deposit offers. Or small cash drops, either through a casino bonus code or from leaderboard tournaments. However, you'll more commonly find deposit bonus offers rather than free casino bonus offers.
All new users need to do is create an account with Betfair, deposit and place a 5 qualifying bet on any of their sports betting markets with odds of 1/2 (1.50) or higher. Once this is settled, players will then receive their 20 in free bets, to be able to be used on any of Betfair's sports markets.