Fix: Dev Error 6635 on COD Warzone and Modern Warfare

Some Call of Duty Modern Warfare players are reporting that they regularly see the Dev Error 6635 error when launching the game, when spectating an online game or when equipping certain skins. This issue is reported to occur on both PC and consoles (PS4, PS5, Xbox One, and Xbox Series X).

Dev Error 6635 on COD Warzone and Modern Warfare
Call of Duty Modern Warfare Dev Error 6635

As it turns out, there are several viable reasons that might trigger this error code on both consoles and PC configurations. Here’s a shortlist of potential culprits that might be responsible for the apparition of this error code when playing COD: Modern Warfare:

  • Ongoing server issue – As it turns out, this issue is often reported whenever there’s an ongoing server issue affecting Activision servers or a platform that the game is launched from. In this case, all you can do is investigate the issue and wait for the involved developers to get the server issue resolved.
  • Permission issue – One of the most common causes of this error code that is entirely within your control is a permission issue. Most likely, the launcher you’re using to launch Call of Duty Modern Warfare doesn’t have admin access so the game files cannot be modified when a new update is available. To fix this issue, you’ll need to run the game in admin mode by re-configuring the game launcher (most likely Battle.Net).
  • Character loadout contains Cold War items – Keep in mind that there’s also an unresolved glitch that might trigger this error if you’re trying to join a game session while using a character that’s using Cold War weapons or skins. In this case, you can avoid the issue entirely by removing these problematic items from your loadout.
  • Corrupted game files – As it turns out, you can also expect to see this error due to a scenario where some of your internal games files are corrupted to the point where the launcher cannot replace or update them. This is reported to happen on both PC and consoles. In this case, you’ll need to reinstall the game and ensure that you leave no remnant files behind before installing the latest version.

Now that you know every potential fix that might be triggering this error code, here’s a list of potential fixes that at least one other affected user has successfully used to fix the issue and play the game normally:

1. Check for server issues

Before you move on to other potential fixes that will resolve the problem locally, our recommendation is to start by checking if this issue is not caused by an ongoing server outage.

The dev error 6635 error code is often times associated with a widespread server issue that is currently affecting matchmaking.

Before you dismiss a scenario like this, you should take a few minutes to confirm or infirm if it’s applicable. This is very likely if you see this error code every time you attempt to connect to Activision’s servers when launching the game.

Fortunately, Activision has a dedicated status page where you can see if the game is currently experiencing server issues.

Checking for Server issues

When you get to the correct page, use the drop-down menu in the top-right corner of the screen to change the current game to Call of Duty Modern Warfare.

Once you select the correct game, see if the status page is currently reporting any issues. If every aspect of the game currently has a green checkmark, that’s probably not the case.

Note: It’s also possible that the platform you’re using to play the game (Steam, Epic Games, or Battle.Net) is currently experiencing issues. You can check if this is applicable by clicking on the platform icon under Server Status by Network.

Checking for a platform issue

Note: If the status page is reporting a server issue, you can also check directories like DownDetector or IsItDownRightNow to see if other users are currently reporting the same kinds of problems.

If you have successfully investigated every possible server issue and found no evidence of a server problem, you can move down to the following fixes presented below.

Else – If you managed to find evidence of a server problem, the issue is entirely beyond your control and you’ll have to wait for the involved developers to fix the problem.

2. Run the game in admin mode (PC Only)

As it turns out, one of the most common causes that will cause this problem when attempting to launch the game is a permission issue. This problem can be facilitated by a strict UAC (User Account Control) policy.

As Activision themselves acknowledge, you’ll need to ensure that the launcher you’re using to launch the game (most likely Battle.Net) has admin access.

If this scenario is applicable to your current situation, you’re most likely seeing the Dev Error 6635 error because Battle.Net doesn’t receive enough permissions to update or change the COD: Modern Warfare game files.

Some users that we’re encountering the same problem have confirmed that the issue was resolved after they modified the main Battle.Net executable in order to ensure that the game always launches with admin access.

Before you get to the actual modifications, you can test if this method is effective before actually enforcing it by right-clicking the Battle.Net executable and choosing Run as Administrator from the newly appeared context menu.

Running Battle.Net with admin access

Next, launch Call of Duty Modern Warfare through the elevated Battle.Net interface and see if the error code is resolved.

If the error doesn’t occur anymore when while it’s launched with admin access, follow the instructions below to ensure that the same problem doesn’t happen in the future:

  1. Right-click on the main Battle.Net executable (or shortcut) and choose Properties from the newly appeared context menu.
  2. After you get to the Battle.Net properties screen, select the Compatibility tab at the top, then check the box associated with Run this program as an administrator.

    Running the program as administrator
  3. Click Apply to save the changes, then close the Properties window and launch Battle.Net again.
  4. Launch Call of Duty Modern Warfare through Battle.Net and play the game normally and see if the problem is now fixed.

If the issue is still not resolved even after you’ve ensured that Battle.Net + COD Advanced Warfare is running with Admin access, move down to the next potential fix below.

3. Remove Cold War Content

If you previously ensured that the problem is not related to a permission issue, the next thing you should check is if your current loadout contains any Cold War skins, guns, or other types of limited content.

This error is commonly reported with cold war weapons with dark matter skin.

In case this scenario is applicable and you only see this error when you attempt to join an online game or spectate it, try removing any Cold War loadout item first.

Modifying the loadout in COD

After you do it, exit the game and launch it again (with admin access) and see if the problem is now fixed.

If the error stops occurring after you have removed any crossed-over Cold War items, you can incrementally add them back to your loadout until you see exactly what loadout item is causing the issue.

4. Reinstall the game

If none of the fixes above have proven to be effective in your case, there’s a big chance that the issue is rooted in some kind of system file corruption that is preventing the game from loading certain UI elements. In this case, you should be able to resolve the Dev Error error by repairing the game (on PC) or reinstalling the game (on consoles).

We’ve created different sub-guides to cover every platform where the game is available, so follow the applicable sub-guide below to treat a corruption-issue problem by repairing or reinstalling Call of Duty: Modern Warfare:

4.1 Repairing the game on PC ( Battle.Net)

  1. Start by making sure that that Call of Duty Modern Warfare is completely closed and no background process belonging to it is running.
  2. Next, open up the Battle.Net application and click on the Games tab from the menu at the top.
  3. With the Games tab selected, click on the Call of Duty Modern Warfare to select it.
  4. After you do this, move over to the right-hand section of the screen and click on Options > Scan & Repair.
    Scan and repair the game
  5. At the confirmation prompt, click on Begin Scan and wait for the operation to complete.
  6. Wait until the operation is complete, then restart your computer and launch Call of Duty Modern Warfare once again to see if the same error code is still occurring when you try to join an online game or when trying to spectate one.

4.2 Reinstalling the game on Ps4

  1. From the main dashboard menu of your PS4 console, go ahead and access the Library menu.
    Accessing the Library menu
  2. Inside the Library menu of your PS4 console, select Games (from the left-hand section of the screen), then move over to the right-hand section of the screen and locate the entry associated with Call of Duty Modern Warfare and press the Options button on your computer.
  3. Next, from the context menu that just appeared, use the Delete option and confirm the operation when asked to.
    Deleting the game
  4. Once the uninstallation procedure is finally complete, reboot your console, then reinstall Call of Duty Modern Warfare once again once the next startup is complete.
  5. After the game gets reinstalled and every relevant update is applied to it, launch it to see if the error is now resolved.

4.3 Reinstalling the game on PS5

  1. Make your way to the main dashboard of your PS5, then select Call of Duty Modern Warfare and press Options (on your DualSense Controller) to bring up the context menu.
  2. From the context menu that appeared on screen, select Delete and confirm at the final confirmation prompt.
  3. Next, select every sub-component of Call of Duty Modern Warfare before clicking ok and starting the uninstallation.
    Uninstalling call of Duty
  4. After the operation is complete, use the main dashboard once again to navigate all the way to the right end of your list of items and access the Game Library menu.
    Uninstalling call of duty modern warfare
  5. Once the list of Library games is fully loaded again, navigate to the game you’ve just reinstalled, select it by pressing X, then hit the Download button and wait for the operation to complete.
  6. Once the game is re-downloaded and installed once again, restart your system before opening it for the first time and see if the error is now fixed.

4.4 Reinstalling the game on Xbox One / Xbox Series X

  1. From the main dashboard of your Xbox One console. Start by clicking on the Xbox button on your controller, then use the guide menu that just appeared to access the My games & Apps menu.
    Accessing the Games & Apps menu
  2. Once you’re inside the Game & Apps menu, scroll down through the list of installed applications and locate Call of Duty: Modern Warfare.
  3. After you discover the listing associated with Overwatch, press the Start button and choose Manage game from the newly appeared context menu.
    Managing the game
  4. Once you reach the next menu, select Uninstall all, then follow the on-screen instructions to uninstall both the base COD: Modern Warfare game + every add-on.
    Note: Don’t worry about this operation affecting your character data, load-outs, etc. This data is safely backed up on Activision’s cloud and will not be touched by the reinstallation procedure.
  5. After the uninstallation is complete, reboot your console the go-ahead and reinstall Call of Duty Modern Warfare from scratch using its store listing.
  6. Launch the game once again and see if the problem is now fixed.

Kevin Arrows

Kevin Arrows is a highly experienced and knowledgeable technology specialist with over a decade of industry experience. He holds a Microsoft Certified Technology Specialist (MCTS) certification and has a deep passion for staying up-to-date on the latest tech developments. Kevin has written extensively on a wide range of tech-related topics, showcasing his expertise and knowledge in areas such as software development, cybersecurity, and cloud computing. His contributions to the tech field have been widely recognized and respected by his peers, and he is highly regarded for his ability to explain complex technical concepts in a clear and concise manner.