Why this answer matters
A USB-C cable that charges correctly may still be USB 2-only. If the phone negotiates through a slow cable, hub or host port, the iPhone's USB 3 capability will not appear in real transfers.
2 requirements3 verification steps1 primary source
Requirements
What has to be true
- USB 3-capable cable rated for the target data rate.
- USB 3-capable host port/hub and destination storage.
Verify it yourself
Use this test sequence
Change one variable at a time so you know which requirement made the difference.
- 1
Remove hubs and test direct to a known USB 3 host port.
- 2
Use a known 10-Gb/s-capable cable.
- 3
Compare with a fast local SSD before blaming the phone for a slow network/cloud transfer.
Limits
What this answer does not prove
- 10 Gb/s is a maximum signaling rate, not guaranteed payload throughput.
- DisplayPort and charging can work through paths that do not provide 10-Gb/s data.
Relevant DeviceOK checks
Test the part you can observe
Data Transfer Time CalculatorEstimate ideal transfer time from data size and an entered link rate.
→USB-C Display Path Readiness CheckCheck four documented prerequisites for sending video through USB-C, Thunderbolt, a dock, cable or adapter to a display.
→USB-C Cable Power Rating CheckCompare an entered cable wattage rating with the power you want to carry, while keeping protocol/e-marker limits explicit.
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