Wirebook › Glossary › E-marked cable
What is an e-marked USB-C cable (and when do you need one)?
In one sentence: A USB-C cable with a tiny chip in its plug that tells the charger it can safely carry 5 amps, so laptops can charge at 100 W or more instead of 60 W.
A little more
A USB-C charger won't send more than 3 amps down a cable unless the cable proves it can take more. Cables rated for 5 amps carry a tiny electronic marker chip (an e-marker) in the plug, and the charger reads it during the USB Power Delivery conversation. With it, a charger can deliver 100 W at 20 V, or up to 240 W at 48 V with the newest Extended Power Range (EPR) cables; without it, everything is capped at 60 W.
That's why a big laptop on a 100 W charger can still show a slow charger warning, or lose battery while gaming, if the cable is an ordinary one. Look for 100 W, 240 W or 5 A on the cable or its packaging. Thunderbolt and USB4 cables are always e-marked. USB-A to USB-C cables have no e-marker and can't do Power Delivery at all.
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