How it works

Without the chip, the port assumes the safe default: 3A and USB 2.0. A USB-C cable with no e-Marker cannot promise more. At 20V that is about 60W. Once a cable needs 5A (100W at 20V, or 240W at 48V under EPR), or needs data above USB 2.0, the USB-IF requires an electronically marked plug. The e-Marker sits in the connector and answers a short query: max current, max voltage, and what data / alt-mode rates the copper can carry.

Power and data are separate ads on the same chip. A 100W charge-only cord can be e-Marked for 5A and still be USB 2.0 with no video. A USB4 or Thunderbolt cable is always e-Marked so it can advertise 20/40/80 Gbps and DisplayPort / Thunderbolt alt modes. Listings usually say "e-Marked," "5A," or both; the USB-IF name for the chip is e-Marker.

USB-PD is the power handshake between brick and device. The e-Marker is the cable's passport in that conversation. PPS on the brick still needs a 5A e-Marked cord above 60W, see PPS.

When it matters

It matters the moment you want more than ~60W through USB-C, or high-speed data / a dock link. A MacBook that asks for 96W or 100W will fall back near 60W on an unmarked cord even if the GaN brick is rated higher. Phone overnight charging almost never needs it. Shopping bars that say 100W, 5A, or e-Marked are the ones that claim the chip.

It also matters for docks and external SSDs: a charge-only e-Marked cable will power the laptop and still starve the high-speed lanes. Match the listing to the job, wattage for charge, Gbps / Thunderbolt for data.

Two catalog cables that declare the chip in different ways: a charge-focused 100W pack, and a USB-IF certified cable built for higher data.

The Anker 100W 6 ft 2-pack lists Power 100W (20V/5A) and E-Marker Yes. It is the charge-desk default: confirmed 5A e-Marked cords for desk and bag, USB 2.0 data only, no video. View on Amazon when the shopping bar is 100W charging and you do not need a dock link.

The Cable Matters USB-IF 20Gbps USB4 cable is e-Marked for high-speed data as well as charging: USB-IF certified 20 Gbps, useful for dock links and faster external storage where a charge-only cord would bottleneck. View on Amazon when the cable has to carry more than USB 2.0.

For lengths, 100W shopping bars, and charge-vs-data picks, read Best USB-C Cables Rated for 100W Charging. For the power handshake the chip sits inside, see USB-PD. For dock-class links that always need an e-Marked high-speed cord, see Thunderbolt.