The Witness is a first-person adventure game with a strong focus on puzzles and it is set on an abandoned island. It starts with an unnamed protagonist at the end of a tunnel. The exit leads to a large, uninhabited island with various modern structures. Almost immediately the island can be explored entirely and in any direction without restrictions. The small story elements are revealed indirectly, but the main goal is to regain memory and find a way off the island. Clues can often be found through elements in the environment and there are also some audio segments, usually with quotes from very different contexts, that can be found through left behind audio logs.
The main focus is the exploration of the island and solving more than 500 puzzles in different forms. No guidance or help is provided and the player has to figure out the mechanics through trial and error, logic or careful observation. The puzzle mode is accessed through a click or button, allowing the character to interact with electronic panels in the environment that usually represent a single puzzle. Most of these puzzles have a maze-like structure with a starting point and an end. A puzzle is solved by connecting start and end in a specific way. This often activates power, through cables, opening up a part of the environment or activating another panel. Through small effects or by following the cables, the effect can be traced. The general concept of the puzzles is largely the same for all of them, but many variants are introduced, such as separating maze items in a certain way, taking into account tetromino shapes, using colours and so on.
There are often panels in areas that gradually introduce new elements, but the player can still tackle them generally in any order. A large amount of puzzles cannot be solved through logic alone, but requires more thorough observation of the environment, similar to the Myst games. Some patterns can only be found on other locations or require the manipulation of parts in the environment that are not obvious. The puzzle mode can be accessed at any moment and this is often used in very different ways, but still according to the concept of the panels. Next to walking on foot, a boat is discovered soon to circle the island and get around quicker.