I am encountering lag problems when I play - what can I do?
For the purposes of this article, lag is defined as high network latency interfering with gameplay - it is recommended that you review the Troubleshooting Game Performance Issues - Software topic first to ensure that your machine is optimized for gaming before reviewing the steps below to reduce lag while playing online:
If you are attempting to connect to a server that is geographically distant or if you are not using a high-speed connection it is important to check the server's Latency (this will appear to the left of the window in the server browser).
Latency represents the amount of time it takes information to reach the server from your machine - higher latency means a greater likelihood of lag.
Games such as Left 4 Dead automaically detect which region you are in, helping to determine the best server to connect you to. You can double-check your region by starting Steam, going to Steam > Settings > Downloads tab and under Download region and selecting the region that you are in or the one closest to you.
Background applications - especially programs which require bandwidth (chat clients, FTP programs, web browsers, etc) - may contribute to choppy gameplay, a low framerate, and other symptoms of lag.
Please see the Programs Which May Interfere with Steam topic for instructions to disable any unnecessary background applications before loading Steam.
It is important to maintain an appropriate environment for your router and other electronics. Ideally, your router should be in a well-ventilated area where it will not overheat. Overheating routers have been reported to cause network connectivity issues and symptoms of lag.
In addition to ensuring your router is operating at optimum levels, it may be useful to forward gaming-related ports to your machine if you are the only user on your home network who will be playing Steam games. Please see the Required Ports for Steam list to see which Steam and game ports to forward.
The Client Rate setting determines how many packets the game server sends to your machine to keep it synchronized - if this rate is set too high you may be missing some of the game data (which will cause lag).
Please see the Setting Client Rates topic if you would like more information on experimenting with your Client Rate setting to determine if a lower rate will reduce lag over your connection.