Glitching is an activity in which a person finds and exploits flaws or glitches in video games to achieve something that was not intended by the game designers. Gamers who engage in this practice are known as glitchers. Glitches can help or disable the player.
"Glitching" is also used to describe the state of a video game undergoing a glitch. The frequency in which a game undergoes glitching is often used by reviewers when examining the overall gameplay, or specific game aspects such as graphics. Some games such as Metroid have lower review scores today because in retrospect, the game may be very prone to glitches and be below what would be acceptable today.
Video game glitches that go "out of bounds" are mostly performed by either moving through walls or corners or jumping to places in the map that do not have invisible walls. For example, in Tony Hawk's Underground 2, in the L.A. level there is a glitch that can allow players to leave the provided play area and pass through the background. Another example of this is a glitch on the Nürburgring track in Gran Turismo 5 where if the player squeezes through any gap between the walls, the car can drive through the scenery and under the paved course and can finish a lap or the race faster than usual by driving directly under the finish line in the direction of the race's path. Another example in the Need for Speed series is Need for Speed: World. In Rockport there is a spot where you can glitch in Point Camden near Bay Bridge.
In "out of bounds" areas, many maps have hollow objects that the player can move through freely. These objects usually are in the distance and are for decoration. The floor or terrain can also be hollow. The floor can appear the same as a normal floor, but moving over it will cause the player to fall as if it does not exist. Depending on the game, after falling a certain distance the player will freeze, die, respawn on the map again or just keep falling. Two good examples are the Nintendo 64 games The Legend of Zelda: Ocarina of Time and The Legend of Zelda: Majora's Mask. In the former, there is a section of "wall" at the entrance to the water temple that will allow players to fall through the ground. Eventually players respawn rather than the game crashing. In the latter, there is a 3-day cycle (after which the moon will fall) that can be surpassed by going to the observatory and looking out the telescope on the last minutes of the final day. If you look out the telescope while the timer is counting down and exit the telescope when the timer hits 0, (if you're lucky) the timer will be gone and you can continue the game without it. The glitch is removed when you play the Song of Time.
Many other glitches may also include background music being played at the time it was not intended to play, such as the Western Super Mario Bros. 2 (based on the Japan-only game Doki Doki Panic) has a glitch where the Subspace music (the Overworld background music from the original Super Mario Bros.) can be played outside of Subspace after the player becomes invincible and enters Subspace and leaves before invincibility drains away (this was fixed for Super Mario All-Stars and Super Mario Advance so Subspace music can only be played in Subspace). One of the best known examples for glitching in an online game is Grand Theft Auto: IV, where people can glitch into rooms they're not supposed to, or get under the map (for example by glitching a helicopter to spawn under the map and fly into beta rooms). Transformers: War for Cybertron is also known for glitching and hacking. Glitching Players are able to edit the classes far beyond regular players. The two almost make the game unplayable because of the cheating from the glitching and hacking.
Sometimes these glitches involve strange A.I. behaviors and mannerisms. Extreme Paintbrawl, often considered by many as one of the worst video games ever produced, featured an A.I. that often ran against the walls and appeared to moonwalk across maps instead of realistically walk. Another such glitch can be found in Big Rigs: Over the Road Racing, where there is no script programmed for the computer opponent A.I. to carry out. Therefore, the opponent never moves at all.
Some games you can take advantage of the programmers only assuming that you will have positive values for things like money and when a negative value is acquired you can then get near-unlimited money. An example of this is in FIFA 11 where if you have a player on loan and no money left in the transfer budget, you can cancel the contract and the game will not check for a negative value. Once the loan is cancelled, the money is subtracted from the player resulting in a negative money value that then overflows back to the top of the positive value possibilities, resulting in the player having near the highest amount of money possible.
There are also physics glitches, such as the glitch with the swingset in Grand Theft Auto: IV, where if the player climbs on top of the swingset, the shaking of its chains will cause the physics to oversell the impact and send the player flying a great distance away. Since GTA III, if the player stands in a Gate or if you're in Car (but still in an gate) and the Gate is closed, then you will be jumped to the Sky.
Some glitches occur randomly, as with a glitch in NCAA Football 11 which will cause the football game to run longer than the time indicated on the clock and, most often, indefinitely.