Online casinos can be divided into three groups based on their interface: web-based casinos, download-based casinos, and more recently live casinos. Some casinos offer multiple interfaces.

Web-based casinos: Web-based online casinos are websites where users may play casino games without downloading software to the local computer.

Download casinos: Download-based online casinos require the download of the software client in order to play and wager on the casino games offered. The online casino software connects to the casino service provider and handles contact without browser support. Download-based online casinos generally run faster than web-based online casinos since the graphics and sound programs are located within the software client, rather than having to be loaded from the Internet. On the other hand, the initial download and installation of a download-based online casino client does take time. As with any download from the Internet, the risk of the program containing a virus does exist.

Live casinos: Live-based online casino lets players interact with games played in a real world casino environment. Online players can see, hear, and interact with live dealers at tables in casino studios worldwide.

Some casinos offer multiple products such as poker, bingo, skill games, lotto, and sports betting. Many larger online casinos label themselves as sportsbook, racebook, and casino. Signaling that you can bet everything online.

Another big difference with online casino is the bonuses they offer. Most online casinos offer signup bonuses to new players making their initial deposit. Such bonuses usually equal a percentage of the player's deposit, and almost all online casino signup bonuses require a minimum rollover before a cash out.

There is a difference in the odds between the "play for fun" version and the real money versions of online games. Although it can't be confirmed, trying out the "play for fun" versions at several online casinos often results in hefty imaginary bank accounts. If the real money games also paid off that big, the casinos would quickly go bankrupt. Success in the "play for fun" games doesn't equal success when real money is on the line.