Call of Duty: Modern Warfare 3 (2011) — 2-Player Online Co-op Status

No official 2-player online co-op mode exists in MW3 (2011).

What MW3 Actually Offers

• Spec ops (2-player co-op): Offline splitscreen or online 2-player (separate consoles, each needs copy + Xbox Live Gold/PSN). Missions are standalone, not campaign.
• Survival mode (spec ops): 1-2 players, wave-based, online or splitscreen.
• Campaign: Single-player only.
• Multiplayer: Competitive 6v6+; no co-op.

Common Confusion

Players often conflate spec ops with campaign co-op. MW3 does not support 2-player story campaign online.

If You Want Campaign Co-op

• MW2 (2009) — no campaign co-op.
• MW2 (2022) — yes, 2-player online campaign co-op (post-launch update).
• Black ops 3 / cold war / MWII (2022) — 2-4 player campaign co-op.

For the 2011 title: grab a friend for spec ops/survival, but solo the campaign.