Apple has updated its USB-C Digital AV Multiport Adaptor, a dongle you plug into your Mac or (newer) iPad Pro so you can connect an external display or standard USB device. Here are the specs and details.
The newer version of its Multiport Adaptor adds support for HDMI 2.0, which includes:
4K UHD and 60 Hz video playback
HDR support (HDR10 and Dolby Vision)
These are excellent upgrades over the previous USB-C AV Multiport Adapters, which only supported HDMI 1.4b. While Apple has discontinued the older version of the adaptor, and now sells the new version at its official store (online or retail), it will take a bit of time before the older adapters are gone from other store shelves.
To ensure you’re picking up the newer dongle, make sure you check for model number A2119 on the packaging (older models are A1621).
While the adaptor will work with any Apple device that has a USB-C connection, you’ll only be able to max out the HDMI 2.0 connection (driving a 3840-by-2160 resolution display at 60Hz) if you have one of the following devices.
15-inch Mac Book Pro (2017 model or newer)
Retina iMac (2017 model or later)
Your device will also have to be running macOS Mojave (10.14.6 or later) or iOS 12.4 (or later).