Guide
What Is DisplayPort Alt Mode?
DisplayPort Alt Mode is a specification that lets a USB-C port carry a native DisplayPort video signal alongside (or instead of) USB data, over the same physical connector and cable.
How it works
USB-C's physical connector has enough high-speed lanes that, when both ends negotiate DisplayPort Alt Mode, some of those lanes are reallocated to carry DisplayPort's native signal directly — not converted or re-encoded. This is why a USB-C monitor with a DP Alt Mode input can be driven with a single cable, with no separate video adapter box in between.
Why it matters for adapters
Because the signal on the wire is native DisplayPort, a simple passive DisplayPort-to-HDMI adapter can convert it to HDMI — no active electronics or extra power required, unlike some other cross-standard conversions. This is why a USB-C (DP Alt Mode) laptop port can drive an HDMI-only monitor with just a passive adapter.
Not the same as Thunderbolt or USB4
Thunderbolt and USB4 ports also carry DisplayPort, but through a broader tunneling protocol that includes PCIe and other traffic, not through DP Alt Mode itself. A port can support DP Alt Mode without being Thunderbolt- or USB4-capable, and the reverse doesn't automatically follow either, though in practice Thunderbolt/USB4 ports almost always support DP Alt Mode as part of their spec.
See it in a real device
Laptops that charge over USB-C
Verified examples from our database (highest charger wattage per brand):
- Lenovo Legion Slim 5 16AHP9charges over USB-C, 140 W recommended
- MSI Titan GT77 HX 13VIcharges over USB-C, 100 W recommended
- ASUS TUF Gaming A15 (2024)charges over USB-C, 100 W recommended
- Framework Laptop 13 Pro (Intel Core Ultra Series 3)charges over USB-C
- HP EliteBook X G1a 14 inchcharges over USB-C
- MacBook Air (13-inch, M5, 2026)charges over USB-C