Just spin the reels of the slots games at free online casinos that provide you real no deposit bonuses. Playing slots is the easiest way to play online casino games. Best Online Slots: Highest Paying Slots Explained Start with the high RTP Ugga Bugga video slot. Most of the world’s popular and high-paying online slots are accessible in legal US mobile casinos. Slots are hugely popular and players everywhere seek them for top payments and big cash wins. Online slots are the bread and butter of online casinos.