Diep.io is a browser-based action-shooter released in 2016, known for its simple but addictive gameplay and popularity among casual gamers. While its peak was years ago, it retains a niche audience due to easy access (browser/mobile) and support from publishers like Miniclip and Addicting Games. Modern estimates suggest that around 10,000-20,000 players still play daily across web and mobile, typical for older .io titles.