Fix: ‘Dev Error 6634’ Call of Duty: Modern Warfare on PC, PS5 and Xbox

Dev Error Code 6634 is a commonly reported issue on PC, PS5, and Xbox Series X / Xbox Series S. This issue is caused by a bad cache of Call of Duty Modern Warfare on PC or It can be an issue with bad Installation of Multiplayer Packs on Consoles.

After checking various user reports and trying to replicate the issue locally, it turns out that there are several underlying scenarios that will cause the 6634. Here’s a shortlist of potential culprits:

Now that you are aware of every potential scenario that might be responsible for the apparition of the 6634 error code, here’s a shortlist of fixes that other users have successfully used to play Call of Duty Modern Warfare without seeing this error code again.

Unequip the Watch item

As it turns out, one of the most common instances that will 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 actions.

One infamous combination that is known to cause this problem is when players attempt to use the Stitch operator with ANY Cold War watch. 

If you find yourself in this particular scenario and your loadout currently contains an equipped watch, follow the instructions below to attempt to resolve the issue by unequipping your Call of Duty Modern Warfare watch item:

1. Open Call of Duty Modern Warfare and make sure you’re on the main menu of the game.
2. Next, select Weapons from the Ribbon menu at the top.

   

3. Once you’re inside the Weapons menu, go ahead and access the Watch Select sub-menu.

   

4. Inside the Watch Select menu, ensure that the toggle associated with the option is set to None before saving the changes.

   

5. Now that the watch is successfully unequipped, you can select any operation you want and it should no longer cause the same conflict that was triggering the error code.

If you made this adjustment and you still see the 6634 error when you attempt to join a multiplayer game, move down to the next potential fix below.

Uninstall the MutiPlayer Pack 2 and MultiPlayer Pack 3 (Consoles Only)

If the first potential fix was not effective in your case and you confirmed that Cold War content has nothing to do with this error, the next thing you should do is ensure that you’re not deal with a common cause of a broken MultiPlayer Pack 2 or MultiPlayer Pack 3 content.

This is very common on Xbox Series S, Xbox Series X, and PS5. (Consoles that allow you to partially install games)

What usually happens is one of those Multiplayer packs (or both) becomes corrupted when a new update is installed and up interfering with the stability of the game.

In case you find yourself in this particular situation, you should be able to fix the problem by temporarily uninstalling these 2 problematic Multiplayer packs from your Playstation or Xbox console before installing them back.

Depending on your console of choice, follow sub-guide 1 or sub-guide 2 to fix the problem in your case:

Reinstall MultiPlayer Pack 2 & 3 on Xbox Series X or Xbox Series S

1. From the main dashboard of your Xbox console, access the Settings menu (either via the Xbox button or directly from selecting the gearbox icon on your screen).

   

2. From the context menu that just appeared, select My Apps & Games from the list of available options and press A to access the menu.

   

3. From the next menu, select Apps and wait until your library of available games is fully loaded.
4. Next, ensure that Games is selected from the vertical menu on the left, then move over to the right-hand side pane and access the entry associated with your Call of Duty game.

   

5. From the context menu associated with Call of Duty Modern Warfare, go ahead and access the Manage game and add-ons menu.

   

6. From the Manage menu of your Call of Duty game, select the main interface at the top of the screen to get an overview of every game piece.

   

7. Once the list of game pieces is fully loaded, unselect everything first to make sure you’re not deleting anything by mistake.
8. Next, check the boxes associated with Call of Duty Modern Warfare – Multiplayer Pack 1 and Call of Duty Modern Warfare – Multiplayer Pack 2.

   

9. Once the problematic packages are selected, follow the on-screen prompts to uninstall them from your console, then restart your console.
10. After your console boots back up, launch the game normally and install the missing multiplayer packs when prompted to do so, and check if the Error Code 6634 error is now fixed.

Reinstall MultiPlayer Pack 2 & 3 on Playstation 5

1. From the main dashboard of your PlayStation 5 system, access the gearbox icon (settings) in the top-right corner of the screen.

   

2. Once you’re inside the Settings menu of your PlayStation 5 system, access the Storage submenu.
3. Inside the Storage sub-menu, select Console Storage from the menu on the left, then access the Games and Apps menu from the right-hand section of the screen.

   

4. Once you’re inside the Games and Apps menu, scroll down through the list of installed applications and locate the entry associated with Call of Duty.
5. When you locate the correct entry, access the Manage menu associated with the game (select it, then press X to access it).

   

6. Once you’re inside the Manage menu of Call of duty, go ahead and select Multiplayer Pack 2 and Multiplayer Pack 3 before clicking Ok to schedule them for deletion.

   

7. At the confirmation prompt, click Ok to confirm the uninstallation of the problematic Multiplayer packs, then reboot your console.
8. After your console boots back up, launch the game once again and see if the same problem is still occurring.

If the 6634 dev error is still an issue in your case, move down to the next potential fix below.

Cleaning the Battle.Net Cache (PC Only)

If you’re seeing the Dev Error 6634 on PC while booting the game using Blizzard’s launcher (Battle.Net), chances are you’re dealing with some type of corrupted cache issue.

This has been confirmed by several users that we’re unable to join or maintain a stable multiplayer connection. 

Some affected users have confirmed that they managed to fix the issue indefinitely by navigating to the location of the Blizzard Entertainment folder (the one that holds the cache folder) and delete every file there in order to clear the cache.

If this scenario is applicable to your current situation, here’s a quick guide on clearing the Battle.net cache in order to resolve the Dev Error 6634:

1. Start by ensuring that Battle.net any game opened through it is currently closed.
2. Press Windows key + R to open up a Run dialog box. Next, type ‘%ProgramData%‘ and press Enter to open up the ProgramData folder.

   

3. Once you get to the ProgramData folder, go ahead and access the Blizzard Entertainment folder, then navigate to Battle.net > Cache.
4. Inside the Cache folder, select everything inside with Ctrl + A (or by using your mouse cursor to select everything), then right-click on a selected item and choose Delete from the newly appeared context menu.

   

5. After the entire cache folder has been cleared, restart your computer and launch Call of Duty once again once the next startup is complete.

If your attempts at connecting to Multiplayer games (regular, competitive or Zombie Mode) end up with the same 6634 dev error, move down to the next potential fix below.

Reinstall Game Shaders (PC Only)

According to some users that we’re also dealing with this particular issue, it’s not uncommon for this issue to be caused by a glitched shader cache that is causing the game to crash.

Fortunately, you can resolve this issue fairly easily by accessing the game’s Options menu and forcing the reinstallation of the Shaders.

This procedure has been confirmed to be effective by a number of users that have been dealing with the dev error 6634.

If this scenario looks to be applicable to your particular situation, follow the instructions below for steps on clearing & reinstalling the Shaders Cache in Call of Duty Warzone:

1. Open the game normally and wait until you get to the initial screen.
2. From the list of available game modes, select Warzone and wait for the game to boot.

   

3. Inside the Warzone screen, access the Options screen, then select the Graphics tab from the horizontal ribbon menu at the top.
4. Next, scroll through the list of options and locate the entry named Restart Shaders Installation.

   

5. At the confirmation prompt, click on Restart and wait until the shader installation is complete.
   Note: Expect this operation to take several minutes and increasingly longer if you’re not using an ultra-fast SSD.
6. After the installation of the game shader is complete, launch Call of Duty once again and see if the problem is now resolved.

In case you are still seeing the 6634 dev error when attempting to join a multiplayer game, move down to the final potential fix below.

Uninstall the game and install Warzone ONLY

If none of the potential fixes above have worked in your case and you’re experiencing this issue with Warzone, you should be able to avoid the issue completely by uninstalling the game and strictly installing Warzone – without the single-player campaign, zombie mode, or multiplayer component.

This is certainly limiting if you enjoy playing multiple Call of Duty modes, but it’s a fix that a lot of Warzone players have successfully deployed on both PC and consoles.

Whether you’re a PC or console gamer, follow one of the sub-guides below to uninstall your current Call of Duty installation and install the standalone version of Warzone:

Uninstall COD and install Warzone (standalone) on PC via Battle.Net

1. Press Windows key + R to open up a Run dialog box. Next, type ‘appwiz.cpl’ inside the text box and press Enter to open up the Programs and Features menu.

   

   Note: If you are prompted by the UAC (User Account Control), click Yes to grant admin access.

2. Inside the Programs and Features menu, scroll down through the list of installed programs and locate the Call of Duty entry.
3. When you finally discover the Call of Duty entry, right-click on it and choose Uninstall from the context menu that just appeared.

   

4. Inside the uninstallation screen, follow the on-screen prompts to complete the process then restart your computer.
5. After your computer boots back up, open the Battle.Net app and sign up with your account credentials.
   Note: If you don’t have Battle.Net installed on your computer, you can download the latest version and create an account on this official Blizzard page.
    
6. Once you are successfully signed into the Battle.Net app, click on All games at the top of the screen, then click on Warzone from the available library of games.

   

7. Once you’re inside the correct listing of Warzone, click on the Install button in the bottom-left corner of the screen.

   

8. At the next screen, configure your Warzone installation and hit Start Install when you are ready to go.
9. After the installation is finally complete, open Warzone and see if you still get the same dev error when you attempt to join a multiplayer game.

Uninstall COD and Install Warzone (standalone) on PS5

1. From the main dashboard of your PS5 console, use the left thumbstick on your controller to select the Call of Duty listing.
2. Next,  press Options (on your DualSense Controller) and bring up the context menu.
3. Once you get to the next context menu, select Delete and confirm once asked to do so.
4. At the next management menu, select every sub-component of Call of Duty before clicking ok and starting the uninstallation.

   

5. Once the operation is complete, return to the main UI dashboard and access the Store component by navigating to the left corner of the dashboard menu.
6. Inside the Store, use the search function to find the standalone version of COD Warzone.
7. Once you’re inside the correct listing, hit the download button and wait until the process is complete.
8. Launch the standalone version of COD warzone and see if the problem is now fixed.

Uninstall COD and Install Warzone (standalone) on Xbox Series X / S

1. On your Xbox Series S or Xbox Series X console, press the Xbox button on your controller.
2. Using the guide menu that just appeared, access the My games & Apps menu.

   

3. Once you’re inside the Game & Apps menu, scroll down through the list of installed applications and locate Call of Duty.
4. After you discover the correct listing, press the Start button and choose Manage game from the newly appeared context menu.

   

5. Once you’re inside the game management menu, select Uninstall all.
6. Next,  follow the on-screen instructions to install Call of Duty + every associated addon.
   Note: Rest assured that data related to your character and online progress is safely backed up on Activision’s cloud and will not be touched by the reinstallation procedure.
7. After the uninstallation is complete, access the Microsoft Store component and download the standalone version of Warzone on your Xbox console.
8. Once the download and installation are complete, launch the game and see if the problem is now resolved.