If you would like to turn on/off crossplay on your console, you can follow the steps below.
In the Fortnite lobby on Playstation:
- Go to the Menu by pressing Start and scrolling down to the gear icon.
- Click on Settings.
- In Settings, go to the Account And Privacy tab.
- Scroll down to Gameplay Privacy to find Allow Cross Platform Play.
- Set to Yes to turn crossplay on or No to turn it off.
on Xbox: refer to https://support.xbox.com/en-US/help/hardware-network/connect-network/multiplayer-cross-network-play