Fix: VAC was unable to verify your game session

There was a very disruptive behavior seen by CS: GO where players would get the error “VAC was unable to verify your game session”. Hence the players are unable to que for matchmaking and play any matches.

VAC is Valve Anti-Cheat System. Its main job is detecting installation files anomalies where files might be manipulated to provide unfair means for players to gain an edge over other people. If you are getting this error even if you didn’t do anything wrong, it means there are problems with the configuration of the files. Start with the first solution and work your way down.

Solution 1: Running Steam as Administrator

The first and foremost thing which we should check is if Steam has administrator access on your computer.

Steam requires full access in order to provide you with the optimal gaming experience. This means changing system configuration files and having a lot of resources and memory at its disposal. Be default, Steam doesn’t have full administrator access.

We can grant Steam full administrative privileges and check if the problem gets solved. First, we should make the changes to the Steam.exe file and later grant the whole Steam directory access as there are various configuration files present in the main directory.

Read our guide on how to grant Steam administrative access.

Solution 2: Verifying integrity of game files and repairing library

Most of the games available in Steam are very huge files consisting of several GB’s. It is possible that during the download/update, some of the data may have been corrupted. Steam has a feature within the client itself where you can verify the integrity of game files quite easily.

This feature compares your downloaded game with that of the latest version present in the Steam servers. Once it is done crosschecking, it removes any unwanted files or updates them if needed. There are manifests present in each computer where a game is installed. Instead of checking the files one by one (which take hours), Steam compares the manifest present on your PC with the one in the servers. This way the process takes place much more quickly and efficiently.

We can also try repairing Steam Library files. Steam Library is the place where all your games are present and you can only access them through it. It is possible that your Steam library isn’t in the correct configuration. There may also be a case where you have installed Steam on one drive and your games are on another one. In that case, you have to repair both the libraries before launching your game again.

Do note that this process takes some times as a lot of computation is going on. Don’t cancel the process in between to avoid any further errors. Furthermore, Steam may ask you to enter your credentials once it is done with the process. Don’t follow this solution if you don’t have your account information at hand.

You can check our detailed guide on how to verify the integrity of games and repair your Steam library.

Solution 3: Repairing Steam Client

If both the above methods don’t work, there is also a chance that your Steam client is either corrupt or has some bad files present. We can fix this by executing a command on the command line. Do note that you might require administrator privileges to perform this solution.

1. Press Windows + S, type “cmd” in the dialogue box, right-click on the application and select “Run as administrator”.
2. Once in elevated command prompt, execute the following command:

"C:\Program Files (x86)\Steam\bin\SteamService.exe" /repair

Here the path located within the colons indicate the location of Steam on your computer. You can change this if Steam is located elsewhere.

3. Wait for the whole process to complete. Then restart your computer and check if this solved the problem at hand.

Solution 4: Power Cycling your Computer

If all the above methods don’t bear any fruit, we can try power cycling your system.

Power cycling is an act of turning off a computer completely off and then on again. Reasons for power cycling include having an electronic device reinitialize its set of configurations parameters or recover from an unresponsive state or module. It is also used to reset all the network configurations as they are all lost when you turn the laptop completely off.

To power cycle your laptop shut it down properly and remove all the wires from it. Next remove the battery properly and detach it. Press the Power button for 1 minute. Now, wait for around 2-3 minutes before plugging the battery back in. The reason for taking out the battery is to make sure that all the capacitors are discharged correctly and all the current data stored in RAM is lost. After turning the laptop back on, check if the problem got solved.

In case of a PC, shut it down completely, disconnect all modules and take out the main power cable. Now after waiting for the required time, plug everything back in and check if this solved the problem.

In addition to the above you can also try:

• You can try restarting your Steam client properly. Go to Steam, change your username, and exit the client by clicking Steam > Exit. Now open Steam again and go into Offline mode. Now go back online and check.
• Make sure you don’t have any network anomalies and the network is running perfectly.
• Check your antivirus software or any third-party program (such as CCleaner). They are known to conflict with Steam.
• If all the above methods don’t work as expected, you can back up your data and reinstall Steam completely.