Watch Dogs is an open-ended game where players can play a genius hacker. The first part of the series is set in a fictionalised version of the Chicago area in 2013 and follows Aiden Pearce, a grey hat hacker and vigilante who seeks revenge after murdering his niece. He has done some criminal acts in the past and caused family tragedies. Now, he uses a so-called central control system (ctOS). Players use this system to track down the culprits who have harmed their families. By manipulating the web player, they can access the ubiquitous surveillance cameras, download personal data about their targets and their locations, and control traffic lights and public transport systems to deter their enemies.

The series combines elements of action, adventure and vehicle play. Players can freely roam the virtual world on foot or using transport and use a variety of weapons and mêlée based combat. Illegal activities such as attacks on civilians other than civilians and police officers provoke an aggressive and often fatal reaction from those in authority. In case of death, players will respawn near the area where they were killed.

In each game, the player will control a hacker who can hack various electronic devices connected to the fictional ctOS system via their in-game smartphone. While most of the abilities granted by ctOS are used to solve puzzles, players can also use it to create chaos and entertain themselves during free roaming at any given time, such as breaking into traffic lights or placing false evidence against NPCs to get the police to arrest them. In each game, players can upgrade and unlock new features and gadgets. The game contains many covert sections where the player must try to avoid detection by enemies and use non-lethal weapons to bring them out quietly. If the player fails to remain undetected, they can still try to kill all remaining enemies, although in most cases they will find themselves overwhelmed..