How-to
USB-C to HDMI adapter limits: port, cable and signal gaps
Your USB-C to HDMI adapter might not work for high-resolution displays. The issue is usually the port, the cable or the adapter itself.
USB-C ports have taken over data transfer and charging, but they have created a new problem: connecting to displays that lack a USB-C input. A USB-C to HDMI adapter can bridge mismatched ports, but Engadget reports that these adapters sometimes fail to send high-resolution video or just show a blank screen.
The problem is a relay. Your device's USB-C port must support video output. That requires DisplayPort Alternate Mode, an optional feature. Without it, the port can charge or transfer data but won't carry video. Thunderbolt ports, which use the same USB-C connector, include video by default. Check the manual or online specs to confirm what your port supports.
Even with a video-capable port, you need a fully-featured cable. A basic USB-C charging cable won't transmit video signals. Then the adapter or cable itself must convert the DisplayPort or Thunderbolt signal into HDMI. The weakest link in this chain -- port, cable, adapter or HDMI standard -- limits the final quality.
HDMI has gone through several generations. The highest widely available is HDMI 2.1 (Ultra High Speed), which delivers 8K at 60Hz or 4K at 120Hz with up to 48 Gbps bandwidth and support for variable refresh rates, HDR and eARC. HDMI 2.0 is a tier lower, still handling 4K at 60Hz but with only 18 Gbps bandwidth, which makes it less ideal for high-end gaming. Older HDMI 1.4 cables and adapters can reach 4K but at only 30Hz. Engadget advises against using earlier-generation HDMI adapters.
For permanent setups, Engadget recommends a top-rated USB-C hub or a single USB-C to HDMI cable instead of an adapter. The same port and cable requirements apply.
If your laptop has at least two USB-C ports, you can charge with one and power a display with the other.
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