How long can a USB-C cable be?
AnswerIt depends
It depends on speed. Passive USB-C cables are specified to 4 m at USB 2.0, 2 m at 5 Gbps, 1 m at 10–20 Gbps and 0.8 m at 40 Gbps. Longer cables at higher speeds need active electronics (a redriver or retimer) inside the plug. Thunderbolt 4 active cables keep 40 Gbps up to 2 m. Charging alone works on any length up to 4 m.
| Speed | Passive max | Longer runs |
|---|---|---|
| USB 2.0 (480 Mbps) | 4 m | — |
| USB 5Gbps | 2 m | active cable |
| USB 10Gbps | 1 m | active cable |
| USB 20Gbps | 1 m | active cable |
| USB4 / Thunderbolt 40Gbps | 0.8 m | active, up to 2 m (Thunderbolt 4) |
| Thunderbolt 3, 20 Gbps | 2 m | — |
| Optical (fibre) cables | — | 10 m and more, some features lost |
The standards involved
2013
USB 3.2 Gen 2 (10 Gbps)
Double the speed and much better coding. The sweet spot for portable SSDs.
- data: 10 Gbps
- video: No (only via USB-C Alt Mode)
- power: 4.5 W (port)
USB4 (20 and 40 Gbps)
Thunderbolt 3's protocol, opened up as a USB standard. Tunnels USB, DisplayPort and PCIe over one cable.
- data: 20 or 40 Gbps
- video: DisplayPort tunnelled
- power: USB PD required
Thunderbolt 4
The same 40 Gbps as Thunderbolt 3, with the minimums raised so every port behaves the same.
- data: 40 Gbps (PCIe 32 Gbps)
- video: two 4K 60 Hz or one 8K
- power: up to 100 W (USB PD)
USB 2.0
The baseline every USB port still speaks. Fine for keyboards, mice and charging; slow for files.
- data: 480 Mbps
- video: No
- power: 2.5 W (port); more via USB-C/PD