Usually because one of the three parts does not support the profile: the charger, the cable or the device. All three negotiate, the slowest wins, and a cable rated for a lower current is the part that is most often overlooked.
USB-C charging is a negotiation between three parties, and the result is always the slowest of them.
What is being negotiated
The device asks, the charger offers, and they agree on a voltage and a current. Higher-power profiles use higher voltages rather than simply more current, which is why a charger that supports a profile the device does not will fall back rather than force it.
Where the cable comes in
A cable has its own rating, and above a certain current it must carry an electronic marker declaring it. A cable without one is limited regardless of what the charger and device agreed, and nothing reports this as an error — everything simply charges slowly.
The other common causes
A port shared with another device on a multi-port charger. A device that throttles charging because it is warm. A device that deliberately slows near full, which every lithium device does. Each looks like a hardware fault and none is.
How to isolate it
Change one part at a time with a known-good example of the other two. A charger tested with a different cable, then a different device, identifies the limiting party in two attempts — and an inline power meter shows what was actually negotiated rather than what was hoped for.
What people ask before they order
Do USB-C cables really differ?
Substantially. They differ in the current they are rated for, whether they carry an identifier chip, and whether they support the higher-voltage profiles at all. Two identical-looking cables can charge at very different rates.
What about a charger with several ports in use?
Multi-port chargers share a total output budget, and plugging in a second device usually reduces what the first receives. The maker publishes the split, and it is rarely equal.
Last reviewed 16 September 2026