Note: This guide is for the current 21.5-inch and 27-inch iMac. If you’re not sure which iMac you have or want to find information and documentation for other models, see the Apple Support article Connect an external display to your iMac.
Gigabit Ethernet port or 10 Gigabit Ethernet (RJ-45) port: Connect a router or modem to join the internet, or connect to another computer to transfer files without using Wi-Fi. The 27-inch iMac has the option to configure a 10 Gigabit Ethernet port, which provides faster link speeds.
Display: The 21.5-inch iMac has either a Retina 4K display or an LED-backlit display, depending on the model. The 27-inch iMac has a Retina 5K display with True Tone® capability. True Tone technology automatically adapts the color of your display to match the light in your environment for a more natural viewing experience. Turn True Tone on or off in the Displays pane of FaceTime.
Speakers and microphones: The 21.5-inch and 27-inch models include built-in stereo speakers and mics for FaceTime, Siri, and videoconferencing. On the 27-inch iMac, a microphone array delivers studio-quality recordings for podcasts, voice memos, live music, and much more.