Latency

Latency is the time it takes for your computer to communicate with the World of Warcraft server. A latency of 50ms means that it takes 50 milliseconds to send and receive a packet from the World of Warcraft server. For playing games online such as WoW, a low latency is desired as it means less communication time between control input and events happening on the player's screen. A high latency can become a hindrance for proper gameplay. Things that could be experienced are delayed messaging, out of sync battles and difficulty of performing tasks in-game that are required to advance. The terms "Lag" and "Ping" are often used when players refer to their current latency status.

Latency Bar
The Latency Bar measures the speed of your connection to the World of Warcraft server. A green bar means your connection is good. A yellow bar means you may experience intermittent delay, called lag. A red bar means your connection is poor and you will experience significant delay.''

The bar itself was eventually merged into the Game Menu button.

What can affect latency
World of Warcraft requires clients to connect to the Blizzard Servers to play the game. There are four possible breaking points in the transmission of the required communications, which are: the client's computer, the client's router, the client's ISP and finally Blizzard's Servers. In a network such as this, one faulty point causes the whole game experience to suffer. When trying to identify the cause of high latency, consider the following things:


 * The last time a piece of hardware was added to your computer.
 * The last time new software was installed on your computer.
 * The last time drivers have been updated on your computer.
 * The last time your router/modem has been reconfigured.
 * The last time a new patch has been installed for World of Warcraft.
 * The last time settings of the firewall were changed.

Any changes applied can cause devices to function slighly different than before, and as such, be the cause of elevated latency. Most likely, if problems ever do arise, something was done to alter the setup from how it worked before. The official World of Warcraft forums have a Technical Problem section where help can be found to more specifically pinpoint the cause and solve it.

Malware
Remember to keep the computer free from adware, spyware and other malware. These would fall under the category of new software. Since these are applied to a computer without notification or permission of the user, it is easy to overlook these as a possible cause of higher latency.

File-sharing software
Some ISPs punish users of file sharing software by lowering the quality of their connections, which can increase latency. However, this usually stops promptly once the software stops running. With Bell Canada at least, one can use the same connection for both a BitTorrent client and WoW, but not both at the same time.

4.0.6 Changes
In 4.0.6 Blizzard changed the way the latency is displayed. There is now a 'home' and a 'world' latency. The official explanation is the following.