Games developed on Macromedia (now Adobe) Flash's platform – which allows highly compressed animation – make them ideal for the internet. Since flash video games run in a web browser, they require no extra downloads to play. By the early 2000s, more and more were being developed and becoming available for free online.

Flash games remain hugely popular. There are a few main categories of free online games: original games, knock-off or spoof games, and casino-style games. But since they are designed to be easy to learn and play, all these types rely on gameplay developed for programs from the early days of console and PC gaming.

Original Flash-Based Online Games

Much of the flash-based games available online are original games put together by small developers or hobbyists. They are meant to be played like arcade games, with simple mouse- or keyboard-based controls, though some now have passwords which allow players to return to a game after closing the browser.