: You must have the official 1.4.382 update files (often found in legacy community archives).
Are you trying to install this patch on the older 2011 game or the new 2023 version?
As of 2025, official MW3 multiplayer on Steam is a ghost town of hacked lobbies and 200-ping European search queues. But is immortal. Here’s where you find it:
(Sizes are approximate and vary by platform)