A lot of players complain of 'lag' on various maps and servers, but often people aren't describing what they think they are experiencing. There are 2 things that cause 'lag' and they are quite different things. The aim of this guide is to help you learn the difference between them, how to identify which sort of 'lag' your are experiencing, and what you might be able to do about it.

Frames Per Second or 'FPS' is more or less the measure of how well a game runs on your computer. This is the number of new images your computer can generate each second to give the appearance of a smooth moving image. The higher the number, the smoother the image becomes, with low FPS appearing 'choppy' or 'stutter'. The maximum number of frames your PC can generate is determined by 2 things:

1. Your PC's specifications, notably your processor, graphics card and RAM.
   
2. Your graphics settings in game. Your PC may be able to run TF2, but you might not be able to run it at it's maximum settings.

You might also find this video helpful in explaining what FPS is:
https://youtu.be/zL5kOyHWI_E
As a rule of thumb, the more things happening on screen and the more detailed those things are then more computing power is required to generate them. More advanced games with more detailed models, environments, particles and other fancy stuff will take longer to process than a simpler game with less details.

If you notice a drop in your FPS, then is likely because there has been a sudden increase in the number of things your computer is trying to render, so something else is taking up CPU resources.

There are 2 console commands for measuring your FPS in the Source engine, as well as some other options.

• cl_showfps 1 - This command shows your current FPS in the top right of your screen, saying the maps file name and a number. That number is the FPS measurement.
  The text will also change colour depending on how hard your machine is having to work. It will either be Green (good), Yellow (fair) or Red (bad). If you find that you go into the yellow or red too often, then it means your graphics settings may be too many things for your computer to render at a time. Try lowering your graphic settings until you get more green readings.
  
• net_graph 1 - This option displaces a more advanced set of details, including your FPS and ping, which makes it handy for telling if a map is poorly optimized or your connection is. This my preferred choice for testing a maps performance.
  
• Steam in-game display - The Steam client has an option to enable a FPS counter in all games, not just TF2. Open Steam and go to your settings. On the 'In-game' tab, select an option from the 'In-game FPS counter' drop down. Click OK and load your game. Your FPS will be displayed in the
  
• Other software - Programs like FRAPs and nVidia GeForce Experience, or some software with that is provided with high end graphics cards have their own FPS counters which can be enabled or disabled as you wish. I will not include instructions on how to enable these here, instead consult Google with what ever program you have.

A very important part of a map makers job is to try make the map run as smooth as possible for players, by adjusting what is rendered when. A map has good optimisation when players on low end machines can play with high FPS. There is a limit to how much we can do to optimize a map, but we can still try make a map run smoother.

It can be that only certain parts of a map are poorly optimised while other parts are well done. If you get low FPS in one area or when looking in a given direction, then it probably means the area in question is poorly optimized. If however you are the only person experiencing the low FPS, then it could be your computer.

Latency and ping are two closely related concepts that have a huge impact on how fast or slow your Internet connection feels. This is quite an advanced subject, but for the purposes of this guide, it's how fast of an internet connection you have between your computer at home, us at GmodTech, and Valves servers.

In game your ping is measured in milliseconds. The lower the number the better. Most players find a ping of more than 100 to be laggy, though many competitive players dislike pings above 40-50.

When Internet speeds are quoted, figures are usually given in Megabits per second (Mbps), for example an 8 Mbps broadband connection, but this is really only half the picture. A figure in Mbps gives you an idea of the capacity (speed) of your Internet connection but is doesn’t tell you about latency, a measure of time delay from one networked point to another; the other half of the picture.

Consider the analogy of a car travelling at 100 mph from A to B. This might sound fast but gives no indication of whether the car has driven the most direct route; if direct, fine; if from A to C to D to B the journey is going to take longer. So with network traffic; you might have a fast Internet connection, but if the route between the user’s computer and the server being accessed is indirect, response times will be slower.

Our servers are based in London, UK. Players from the UK and Europe will generally have better connections than those who connect from the USA, Russia or further away. You may have very good internet where you live (such as Fiber Optic broadband) but that won't overcome the fact you are further way from our server.

Now I mentioned a moment ago that you have a connection between us and Valve. When you load up TF2 you have a automatically have a connection to Valves item servers, which is what allows you to access your backpack items. When you join a server you become the 3rd connection point in a triangle of computers, as we are also connected to Valve's VAC system.

There are other things that can make your connection feel slow. In most cases it is due to something else being downloaded to your computer while you are playing. This could be something you are doing intentionally like downloading a game off Steam, or it could be a background update for a program on your computer.

If you live with other people who have devices connected to the internet, you may find your connection slows down when they are also online.

Remember, the best case scenario is where you have high FPS with low ping. Conversely the worst case scenario is where you have low FPS with high ping.

The best way to identify check both as the same time is the net_graph 1 command entered into the console, as this displays your FPS and ping in real time. If you have this enabled by default, over time you will become familiar with your computers average FPS count. You ping will vary from server to server and often with the time of day (there can be a slowdown in the afternoons when everyone gets out of school / work and goes online).

When you are in game and suffer a bit of lag, check your FPS and ping counters. Look to see which one has changed.

Normal Ping, Normal FPS

• Everything is normal, nothing to worry about.

High Ping, Normal FPS

• Wait a few moments. Do other people complain of lag or latency issues in the chat? If so it could be the server having a lag spike.
  
• If other people aren't complaining, it may be just you.
  
• Check if you are connected to a server near you or in another country. Many servers include their region in the server name. If you are, try connecting to a different server
  
• Check your task manager for any programs using extra network resources. If you don't want them to run, you might be able to close them down. Or wait for them to finish their job and go back to playing after.

Normal Ping, Low FPS

• Go back to where you were. Does your FPS go back up, or stay the same?
  
• Look what is being displayed on screen, Is there a lot of things happening (lots of players, buildings, weapons on the floor, ect) or is it there nothing really happening.
  
• If you can, wait a few moments to see if it passes. It may be that another program on your computer is using some extra CPU power for a moment.

Low Ping, Low FPS

• See the above two sections. You may simply have the bad luck to be on a far away server while your computer is trying to update.