How long can a USB C to C cable be?

USB C to C cable configurations span multiple versions.  As of this writing at the end of 2022, it spans USB 2 to USB 4.  But, rather than confusing you with different versions which could be meaningless to normal people, I'm going to break it up by speeds first, then version.

Here are the max lengths of cable assemblies, per the USB C spec (Table 3-1 of USB Type-C Cable and Connector Specification*)

Speed	Version	Max Length Meters	Max Length Inches
500 Mbps	USB 2	4	157
5 Gbps	USB 3 Gen 1	2	78
10 Gbps	USB 3 Gen 2	1	39
10 Gbps	USB 4 Gen 2	1	39
20 Gbps	USB 3 Gen 2x2	1	39
40 Gbps	USB 4 Gen 3	0.8	31

 *USB 3 Gen 2x2 is not included in the spec.  We added that for reference.

USB 1 - Now, you may be asking why we didn’t include USB 1 in our list above?  The reality is that it's normally only used in a very low speed device like a mouse or keyboard that already includes a captive cable, so we considered it irrelevant from inclusion.

Going longer lengths than USB spec – Longer lengths can be achieved, but longer lengths will result in a loss of signal integrity and power availability.  Signal quality drops pretty quickly beyond the lengths above, but you'll have to consider your application.  Studio photographers frequently use longer lengths without issue since there is normally not a constant flow of data and power can be obtained from the device or from a separate hub.

What happens if a cable is too long? - Too long of a length may work fine, or for a time.  However, heavy data usage applications, such as industrial / machine vision cameras, that use a constant stream of data will suffer the most.  Longer lengths end up causing data collisions that can cause failure minutes or hours into use.  These can be difficult problems to diagnose if you're not familiar with what you're doing.