Online casinos are okay with people playing for free because it doesn’t cost the casino anything. But at the same time it doesn’t bring any profit either, so they prefer if players eventually start wagering with real money. The reminders to convert to the other mode might get quite annoying.
It begins on the login screen. You need to choose if you want to play for free or with money. While some casinos make both options equal, others will make the real money one more prominent. Some even pre-select it, so that you have to change it in order to enter free play.
Some casinos will use pop-ups to remind you about switching to real money, especially if you just won big or if you’re generally lucky on a particular day. Others will have a message constantly floating around on the screen, which can get very irksome when it covers part of the game for a while, mostly the balance. If you want to learn how payouts work, you need to know your balance and it shouldn’t be covered.
Features will sometimes be missing when you play for free, for example progressive jackpots or Auto Play. Some games might be not available either, for example multi-player table games.
The reminders automatically go away when you switch to a real money account. If you don’t want to do that yet (or at all), you unfortunately have to deal with them to keep playing for free.