Connectivity includes six Thunderbolt 2 ports, one HDMI 1.4 UltraHD port, 4 USB 3.0 ports, and Dual Gigabit Ethernet ports in addition to 802.11ac and Bluetooth 4.0.

Originally, this model reportedly supported as many as three 4K displays or six Thunderbolt displays. However, on June 16, 2015, without updating the graphics cards themselves, Apple quietly increased the official support to as many as three 5K displays (5120×2880) — two using Thunderbolt 2 ports and one using the HDMI port. The support for as many as six 2560×1600 displays using all six Thunderbolt 2 ports remained unchanged.