The PC, PS5, and Xbox One Series X and S frequently experience the development error 6634. On PC, this is caused by a corrupted copy of Call of Duty: Modern Warfare, whereas on consoles it is due to improper installation of the Multiplayer Packs.


Method 1: Remove it From Your Watch Equipment.

As it turns out, one of the most prevalent cases that would trigger the Dev code 6634 with Call of Duty Modern Warfare is a watch + operator combination that makes the game crash during certain in-map operations.

Dev Error 6634

There is a well-known bug that occurs when players try to use the Stitch operator on ANY Cold War watch.

If you find yourself in this predicament and have a watch equipped in your loadout, you can try removing it and resolving the issue by following the steps outlined below in Call of Duty: Modern Warfare.

Step 1: Start up Call of Duty: Modern Warfare, and head to the main menu.

Step 2: Click the top-right arrow and then choose Weapons from the Ribbon menu.

Step 3: Select the Watch Select option once you’re within the Weapons menu.

Step 4: To disable the feature, go to the Watch Select menu and toggle its corresponding button to None.

Step 5: Now that the watch has been unequipped successfully, choosing any action other than the one that was causing the problem code should work.

If you have already tried this and are still receiving the 6634 problem when trying to join a multiplayer game, continue reading below for another possible solution.

Method 2: Clearing Out the Cache On Battle.Net (PC Only)

When starting the game on PC via Blizzard’s launcher (Battle.Net), the Dev Error 6634 indicates a cache corruption. Multiple players have reported that they, too, are experiencing difficulties establishing and keeping an online multiplayer connection.

Users who had this problem say it can be permanently resolved by deleting all files in the Blizzard Entertainment folder (which contains the cache folder) and restarting the computer.

In case this is your situation, here is a quick rundown on deleting the cache to fix the Dev Error 6634:

Step 1: In the first place, you need to make sure that and any games you might have opened through it are closed.

Step 2: To access the Run dialogue box in Windows, use the Windows key plus R. The ProgramData folder can be accessed by typing %ProgramData% into the search bar and hitting Enter.

Step 3: Once you go to the ProgramData folder, go ahead and visit the Blizzard Entertainment folder, then navigate to > Cache.

Step 4: Select everything in the Cache folder by pressing Ctrl + A (or by selecting everything with the mouse), then right-click on a chosen item and select Delete from the context menu that appears.

Step 5: Clear the cache folder entirely, then restart the computer and start Call of Duty again after it has finished loading.

If you keep getting the 6634 dev error whenever you try to join a multiplayer game, whether it’s a standard game, a competitive one, or Zombie Mode, try the next solution.

Method 3: It’s Time To Reinstall The Game’s Shading Engine (PC Only)

Some of the players who are experiencing the same problem as us have suggested that the game crashing could be due to a corrupted shader cache. Thankfully, this is an easy problem to fix: just go into the game’s options menu and reinstall the Shaders.

Many people who have had the dev error 6634 have confirmed that this method works for them. If you believe that this is your circumstance, please read on for details on how to delete and reinstall the Shaders Cache in Call of Duty: Warzone.

Step 1: Simply launch the game as usual and hang tight till the main menu appears.

Step 2: Select Warzone from the list of available game modes and wait for the game to load.

Step 3: When in the Warzone area, go to the Options screen and from there, pick the Graphics option from the horizontal ribbon menu.

Step 4: Next, look for a menu item titled “Restart Shaders Installation” and click on it.

Step 5: If prompted, select Restart, and then wait for the shader installation to finish.

Step 1: Once the game shader has been installed, try starting Call of Duty again to see whether the issue has been fixed.