Thunderbolt 4 / USB4 cables: length
“Passive” Thunderbolt 3 cables reduced in data-transfer rate as they got longer. Anything over 1m and the bandwidth could be reduced to 20Gbps unless the cables were “Active” including special signal boosters at each end, but this significantly increased the cost.
Thunderbolt 4 cables can be up to 2m in length and still reach 40Gbps without the need for expensive Active boosters. Anything over 2m and you need an Active TB4 cable to maintain the high data rate.
0.8m Passive Thunderbolt 3 cable: 40Gbps data transfer rate
1m or 2m Passive Thunderbolt 3 cable: 20Gbps data transfer rate
1m or 2m Active Thunderbolt 3 cable: 40Gbps data transfer rate
1m or 2m Passive Thunderbolt 4 cable: 40Gbps data transfer rate
1m Passive USB4 cable: 40Gbps data transfer rate
2m Passive USB4 cable: 20Gbps data transfer rate
Thunderbolt 4 / USB4 cables: charging
Thunderbolt 4 cables support 100W (USB-C PD 3.0) charging as standard. You can attach a powerful wall charger up to 100W, but note that Thunderbolt and USB-C charging functionality is dependent on your host computer’s charging capabilities. Some Windows PC manufacturers limit charging on their ports. Either way, a TB4 cable is capable of the maximum 100W.
USB-C PD 3.1 now allows for charging at up to 240W. If your device supports charging at over 100W, you’ll need a PD 3.1 cable that supports 240W. This is noted in our reviews below.
Many 240W cables are for charging only, so have a very low data-transfer rate at 240Mbps—but a PD 3.1 Thunderbolt 4 or USB4 240W cable will handle both 240W and 40Gbps data transfer so is far more adept as your principal cable, say between a laptop and a Thunderbolt dock.