Call of Duty: Black Ops Offline vs Online - What Requires Internet?

You don't need internet for all of Black Ops:

Playable Offline

• Single-Player Campaigns: Black Ops 1, 2, 3, Cold War, Black Ops 4—full story, missions, cutscenes.
• Zombies (Some Modes):
  • Black Ops 1 & 2: Certain maps offline.
  • Black Ops 4: Some maps/solo challenges offline.

Requires Internet

• Multiplayer: Team Deathmatch, Domination, etc. need connection.
• Most Zombies Co-op: Multiplayer Zombies requires internet.
• DLC: Downloading maps, weapons, characters.
• Updates: Game patches often need download.

Summary: Core campaign and some Zombies work offline. Multiplayer, co-op Zombies, DLC, and updates require internet.