Which PlayStation 2 accessory allowed the console to play online games?

The PlayStation 2 Network Adapter allowed the console to play online games.

The accessory connected the PlayStation 2 to a broadband or dial-up network, depending on the regional model and setup. It attached to the console’s expansion bay and provided the network connection required by compatible online games.

Some later PlayStation 2 models, especially the slimline redesign, included built-in Ethernet networking rather than requiring a separate adapter. Games such as SOCOM: U.S. Navy SEALs and Final Fantasy XI used PlayStation 2 online functionality.

The Network Adapter is sometimes confused with the Multitap, which expanded the number of local controllers, or the EyeToy, which was a camera accessory. Those devices did not provide internet connectivity.