Watch Dogs is an action-adventure game played from a third-person perspective. Players complete missions—linear scenarios with set objectives—to progress through the story. Outside of missions, players can freely roam the open world of Chicago.
The world may be fully explored from the beginning of the game without restrictions, although story progress unlocks more gameplay content.
In the main game, players take control of Aiden Pearce, a vigilante who can hack into various electronic devices tied to the city’s central operating system (ctOS), allowing various methods for the player to solve numerous objectives. The hacking mechanic in the game is performed directly from Aiden’s in-game smartphone. The phone is also equipped with applications that interact directly with the environment around the player; for example, players can hack into NPC’s phones to retrieve bank data and steal funds as well as unlock new cars, weapons, and in-game music, or they can hack into traffic lights to cause collisions. Players can stop trains, raise security barriers, and black out the entire city and can slow down time to shoot.
The game’s combat utilises a combination of stealth components and limited parkour (there is no jumping up or across), along with the mechanics of a cover-based third-person shooter.
The game allows the players to use non-lethal attacks and avoid killing anyone should they decide to, except the three main antagonists of the game, Damien Brenks, Lucky Quinn and Delford “Iraq” Wade. The hacking element of the game can also be used in combat situations to eliminate opponents, create diversions, or create cover. It can also be used as a stealth tool to sneak past guards. In combat, auto-aim and a cover system are available as assistance against enemies. If players take damage, their health meter will gradually regenerate. If players commit crimes while playing, the police may respond, as indicated by a meter in the head-up display.
Alongside the single-player mode, Watch Dogs features an asynchronous online multiplayer mode. One element to the multiplayer mode is a one-on-one interaction, in which one player secretly joins the single-player experience of another player and attempts to install a “back-door virus” onto their smartphone. In addition, the game features an eight-player free roam mode. Other multiplayer modes include car races, competitive decryption combat, and a ctOS mobile challenge. A mobile application is also available for smartphones and tablets that allows players to challenge another player in-game and use hacks that triggers traps, in an attempt to stop them from succeeding.