Lag (video games)

In computers, lag is delay (latency) between the action of the user (input) and the reaction of the server supporting the task, which has to be sent back to the client.

The player's ability to tolerate lag depends on the type of game being played. For instance, a strategy game or a turn-based game with a slow pace may have a high threshold or even be mostly unaffected by high lag. A game with twitch gameplay such as a first-person shooter or a fighting game with a considerably faster pace may require a significantly lower lag to provide satisfying gameplay.

Lag is mostly measured in milliseconds (ms) and may be displayed in-game (sometimes called a lagometer). The most common causes of lag are expressed as ping time (or simply ping) and the frame rate (fps). Generally a lag below 100 ms (10 hz or fps) is considered to be necessary for playability. The lowest ping physically possible for a connection between opposite points on Earth crossing half of the planet is 133 ms. Other causes of lag result commonly in a lag below a playable 20 ms (50 Hz or fps), or in the loss, corruption or jitter of the game.

Causes

While a single-player game maintains the main game state on the local machine, an online game requires it to be maintained on a central server in order to avoid inconsistencies between individual clients.