Put simply, 40Gbps. Most USB-C ports are built on the second-generation USB 3.1 data-transfer standard, which transfers data at 10Gbps. Thunderbolt 3 and 4 ports, the most common standard, transfer data at up to 40Gbps. Thunderbolt 4 differs very slightly in that it supports a theoretical maximum of 32Gbps for external storage devices, but you probably won't notice the difference. Intel is expected to unveil an 80Gbps version of Thunderbolt this year, called Thunderbolt 5, meaning that you'll see even Thunderbolt docks with even more capabilities when devices release in 2024. There are some exceptions, which you can largely ignore. A new USB 3.2 Gen 2x2 spec can pair two 10Gbps channels together, creating an aggregate 20Gbps hub. (This is really only for external gaming-class SSDs.) And while the vast majority of Thunderbolt 3-equipped laptops are designed with four PCIe lanes for a total of 40Gbps, some laptops only ship with two PCIe lanes for a total of 20Gbps. (A Dell support page, for example, details its four-lane and two-lane laptops.) Essentially, a 20Gbps connection should be enough for a single 4K monitor running at 60Hz, with a bit of extra bandwidth for other data transfers among connected peripherals.) Intel's 10th-gen and 11th-gen Core chips launched in the early days of Thunderbolt, and company representatives say that you can depend on them for 32Gbps of data, not a full 40Gbps. Intel's 12th-gen and 13th-gen Core chips offer the most consistent Thunderbolt experience, with 40Mbps Thunderbolt 4 speeds, including 32Gbps for data transfers to and from storage devices.