A speedrun is a play-through (or a recording thereof) of a video game performed with the intention of completing it as fast as possible. Speedruns may cover a whole game or a selected part, such as a single level. While all speedruns aim for quick completion, some speedruns are characterized by additional rules that players promise to obey, such as collecting all key items. Players attempt speedruns mainly to challenge themselves and to entertain and compete with others.
Players performing speedruns call themselves speedrunners and often record their attempts. These recordings can be seen through many streaming websites or seen on YouTube and are used to entertain others, to verify the completion time, to certify that all rules were followed and that no cheating took place, and to spot ways to improve the completion time further. The use of speedruns as entertainment stems from their conception by game enthusiasts, who would often compare each other's playing skills via videos exchanged over the Internet. As speedruns have grown more competitive, however, enthusiasts often demanded more proper speedrun recordings, so that anyone could verify that a play-through went by the rules it claimed to follow. This verifiability is needed to count a speedrun as an official attempt to beat any previous records.
In order to reach the highest possible quality of play in a speedrun, the player usually has to reason about the game differently from the way that ordinary players might. Speedruns are usually planned out carefully before they are attempted, because the separate areas in which gameplay takes place are often complex and demand skillful play to complete quickly. Speedrunners often exploit imperfectly designed game mechanics to do unexpected and unusual things that save time. Although game mechanics differ widely between games, they often share common traits in the speedrunning context. Many have opportunities to disarrange the intended sequence of events in a game and skip entire parts of it — often called sequence breaking — and many more have programming mistakes, or glitches, that a skillful player can exploit to their advantage.
Some games are considered to be particularly suited to speedrunning and have online communities dedicated to them, which can provide an active platform for discussing, publishing and improving speedruns. Speedruns can be viewed on a variety of platforms, including live streams where players can carry out and share their attempts in real-time. Although speedrunning was originally not a widespread phenomenon, it has since grown to involve several active websites and an increasingly expansive assortment of speedrun videos that are freely and widely circulated on the Internet.