Modern Warfare 4 campaign unlocks October 16, a week before multiplayer
Campaign pre-order access starts a week early, multiplayer waits until October 23

Activision announced Modern Warfare 4's campaign will be playable October 16 for anyone who pre-orders, a full week before the October 23 multiplayer launch. The early window applies to all editions and platforms, per IGN.
This is the third year running Call of Duty has used the staggered rollout. Black Ops 6 did the same thing last fall. The campaign sits on separate servers, so you can finish the story without touching multiplayer progression.
Pre-loading starts October 10. If you're planning to jump in on day one, that gives you six days to clear disk space and sort out shader compilation before the actual unlock. Campaign-only means no Warzone tie-ins yet — those usually come with Season 1 a few weeks post-launch.
Worth the pre-order for campaign alone? Depends how much you care about the story. If you're here for ranked or Warzone, you're waiting until the 23rd regardless.
Run a fresh optimization playbook before October 16 to make sure your rig is dialed in for launch day.