Box art - Call of Duty: Black Ops Cold War

Call of Duty Modern Warfare Warzone dev error 6661 fix

Getting a Call of Duty game to run well seems to be a dodgy proposition for many players. Especially with Call of Duty: Warzone, various error codes often prevent players from joining online matchmaking. One of the latest is dev error 6661, and it seems to affect Warzone, Modern Warfare, and Black Ops Cold War. What does this code mean, and what can you do to fix dev error 6661? Here’s what we know.

Call of Duty | How to fix dev error 6661

Call of Duty - How to fix dev error 6661

While there’s no definitive cause for dev error 6661 yet, it typically appears during Call of Duty online multiplayer sessions. It seems to be a new problem introduced in the latest update for Season One. In most cases, players have reported that they were able to fix dev error 6661 by reinstalling the game.

Given how big Warzone, Modern Warfare, and Black Ops Cold War are, this is not a quick and easy fix. Before you attempt to delete and reinstall the game, it’s worth going through some more basic troubleshooting steps.

  1. Close the game completely, then restart your console or PC
    • Go for a full power cycle — don’t just put the console into rest mode
  2. Double check that your internet connection is working and stable
  3. On PC, try to scan and repair the game through the Battle.net launcher
  4. Where possible, wait for the developers to issue a fix via patch
  5. If all else fails, uninstall and then reinstall the game

The Call of Duty series is no stranger to various error codes, but dev error 6661 is among the most frustrating. It is without any formal definition, and seems to appear at random. No one knows for sure what it means or what causes it. All we do know is that it first surfaced following the recent December 2020 update. As such, we can only assume that the error was caused by the update, and that a patch should fix the problem.

By all accounts, you can fix Call of Duty dev error 6661 by reinstalling the game. Nearly everyone who reported encountering this error code was able to fix it with a fresh install. Still, that’s a lengthy solution for only temporary piece of mind. Until a patch can remove code 6661 for good, it’s worth opening a ticket with Activision Support.