Engadget Guide: How to Tell Whether a USB-C Port Supports Video

Since USB-C was introduced in 2014, it has become the primary connection method for laptops, phones, tablets, game controllers and other devices, Engadget said. The standard has simplified cabling, but the publication noted that some USB-C connections can carry a video signal while others only charge a device. Ideally, every USB-C port would handle data transfer, charging and audiovisual output, but that is not realistic, according to the report.

The key indicator is DisplayPort Alternate Mode, or DP Alt Mode. Engadget said DP Alt Mode is built into many USB-C accessories and allows a USB-C cable to carry video signals using the DisplayPort protocol, a digital display interface that supports high resolutions and fast refresh rates. A single cable can then transfer both data and audiovisual displays. DP Alt Mode requires all three parts, the device, the display and the cable connecting them, to be compatible.

Older USB standards often do not support DP Alt Mode, Engadget reported. USB 3.1 and USB 3.2 devices may support it, but support depends on the manufacturer. Newer connection standards mandate built-in support: USB4 supports both power transfer and video. All generations of Thunderbolt that use USB-C, from Thunderbolt 3 through Thunderbolt 5 and marked by a lightning icon, offer high-speed data and video transfers including DP Alt Mode, according to Engadget. Thunderbolt 3 offers capabilities similar to USB4, while Thunderbolt 4 and 5 provide performance upgrades. The newer versions are more expensive than Thunderbolt 3, but Engadget said they can enhance the experience by powering multiple monitors with better refresh rates and higher resolutions.

Identifying DP Alt Mode compatibility can be difficult. Engadget said some manufacturers label the port type on the device, such as a lightning symbol next to Thunderbolt ports, while others add a DP icon beside a USB-C port. If there are no clues on the device or cable, users should check the manual or search product specifications online to confirm support for DisplayPort Alternate Mode.

If a USB-C port or cable does not support video, Engadget described several workarounds. A device with an HDMI port can use an HDMI cable compatible with both the device and display. Engadget said most modern HDMI cables support up to 8K visuals and high dynamic range, likely producing visual results comparable to USB-C. However, not all HDMI ports and cables are equal; for the highest resolutions and refresh rates, users should choose at least HDMI 2.0, with HDMI 2.1 or later best for modern setups.

For displays without HDMI input, Engadget said an active adapter such as the StarTech USB-A 3.0 to Dual HDMI Adapter can run HDMI output from a USB port that is not normally capable of doing so. Because such adapters rely on internal software and bandwidth, they introduce overhead and are not ideal for gamers or users who want very high resolutions or refresh rates, according to the report. Normal adapters, including USB-C hubs with an HDMI port or USB-C to HDMI cables, will not work if the laptop does not support DP Alt Mode. As a backup, wireless display options like AirPlay or Miracast can cast a display to a TV or monitor without cables.