VAC, or the Valve Anti-Cheat System, was developed by Valve Corporation in 2002 in order to detect modified configuration files or installation files of over a hundred popular games like Counter Strike: Global Offensive, Call of Duty: Modern Warfare, Day of Defeat etc. The aim was to prevent malicious users from exploiting workarounds to get an unfair advantage while playing the game.
It may sometimes happen that even if the mal-users are not modifying the game or its configuration files, VAC may still generate a false positive when a user tries to initiate a matchmaking or an online game session and display a “VAC was unable to verify the game session” error message.
If you, as a malicious user, are using enhancements and/or modifications to exploit or cheat in the game, now might be the time to stop because along with not being able to initiate any more online game sessions or do any matchmaking, you might get blocked sooner or later.
How to Fix VAC Was Unable to Verify the Game Session Error
As a result, you might not be able to recover your progress or any saved data. However, if you are not using any such malpractices, listed below are some methods you can implement to try and avoid the “VAC was unable to verify the game session” error message.
Method #1 Log Out Of Steam And Log In Again
If some configuration files have been altered or modified by the operating system or the file management system of your computer, it may result in VAC not being able to verify them and as a result, it may display the error message.
The first step you can take to get rid of the issue is to log out of your Steam account and log back in with the same credentials. This will delete all the previous configuration files and recreate them upon your log in.
To log out and in again, follow the steps below:
Step 1- Click on the Steam icon on your taskbar, your desktop or your start menu and run the Steam application.
Step 2- Once Steam is running, click on the “Steam” option on the title bar (the topmost bar of the window). Select the “Change User…” option from the menu. In the dialogue box that pops up, follow the instructions.
Step 3- Log back in with your credentials. In case you don’t remember your password, click on the “I Can’t Sign In” option and reset the same.
This will probably fix the “VAC was unable to verify the game session” error and you will be able to start a game session given that the error was caused by any bad configuration or settings.
Remember that just re-installing the game will not resolve the issue because it will load the game with the same files and will not be able to rectify the error.
Re-installing Steam will solve the issue but logging in and logging out is more efficient. In fact in most cases, this method is as efficient as a fresh install. Hence this method is recommended more.
Method #2 Just Reboot Your Computer
If the files that are needed to be verified by the VAC are being accessed by other applications such as the system antivirus or the disk indexing service, the VAC service may be denied access by the operating system in order to avoid read-write conflicts.
This may result in the “VAC was unable to verify the game session” error message.In this case, a simple reboot of your system will do the job.
To reboot your computer, follow the steps below:
Step 1– Click on the Windows icon located at the bottom leftmost corner of your screen on the taskbar or press the Windows key on your keyboard which is generally located at the bottom row.
Step 2– In the Start Menu that appears, click on the power button and select “Restart”. If there are open applications you were working on, make sure to save those and only then reboot your system.
After the reboot, you can open your game and start a new session without the error.
Method #3 Verify Integrity of The Game Files
You can also manually check the integrity of the game files installed in your system to verify whether or not they are exactly as described by the game manufacturer and Steam distributors without any corruption or modifications.
To verify the integrity of the game files, follow the steps provided below:
Step 1– Run the Steam application on your system.
Step 2- Go to the Library tab and you will see a list of the installed games on your system there.
Step 3– Right click on the game you are facing the VAC verification issue with and go to “Properties”.
Step 4– In the local tab, click on the option that says “Verify Integrity of the Game Files”
Step 5– Depending on the size of the game and the type of storage your system has along with any ongoing background activity, the process might take some time.
It is advisable to close any background applications or services not related to Steam that are utilizing the CPU, RAM or Storage resources.
Upon completion of the check, run the game again. The issue will likely to have been fixed.
Method #4 Repair The Steam Client
It could be possible that the Steam client itself may have broken or damaged some files leading to the “VAC was unable to verify the game session” error.
To fix this, follow the steps below:
Step 1– Open up the Run dialogue box on your screen by pressing the Windows and R keys.
Step 2– Type “cmd” in command box and click on “OK”.
Step 3- In the command prompt, copy and paste the following: C:\Program Files (x86)\Steam\bin\SteamService.exe /repair and press enter.
Step 4– In case the path to the SteamService.exe is different in your system, you can replace it with the path of your SteamService.exe
Step 5– Upon completion of the repair, restart your system.
Step 6– After restarting, open the Steam application. It may reconfigure itself or download some files to update or reconfigure. Log in if prompted to.
Begin a game session. Repairing the Steam client may have resolved the VAC verification issue.
Method #5 Exclude Game Directory From Antivirus Scan
As mentioned in Method #3, as the antivirus of your system may try to scan the game directory in the background, it may lead to the VAC service failing to verify the game files.
To avoid this issue, you may opt to white-list the game and Steam directory so that they don’t get scanned automatically. This process, however, is different for different anti-virus software.
The basic procedure is to launch your antivirus software, going to the settings and adding the game directory in the excluded folders list.
Additionally, it is highly recommended that you use a PC Repair & Optimization Tool to rectify common system errors, protect your system from file and data loss, malware, Trojans and/or hardware failures.
You can also use the repair and optimization tool to boost your system for maximum performance.
Hopefully this article helps you in getting rid of the “VAC was unable to verify the game session” error and you can continue to seamlessly participate in online game sessions.