Why this answer matters
USB-C describes the connector, not one universal speed or feature set. Expecting iPhone 15 to transfer at iPhone 15 Pro USB 3 rates can make a normal USB 2 connection look faulty.
3 requirements3 verification steps1 primary source
Requirements
What has to be true
- Use a display cable/adapter that actually supports DisplayPort video for external display use.
- For file transfer, plan around the phone's documented USB 2 up-to-480-Mb/s interface.
- Charging power, video capability and data speed are separate properties of the same USB-C port.
Verify it yourself
Use this test sequence
Change one variable at a time so you know which requirement made the difference.
- 1
Confirm the phone is iPhone 15 rather than iPhone 15 Pro.
- 2
For a display issue, test a known-good USB-C video adapter/cable directly without a hub.
- 3
For a data-speed complaint, compare the observed result with the model's USB 2 ceiling before replacing hardware.
Limits
What this answer does not prove
- 480 Mb/s is the USB 2 signaling maximum, not guaranteed file-copy throughput.
- A charge-only or low-capability cable can still prevent data/video even when the phone supports the feature.
Relevant DeviceOK checks
Test the part you can observe
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.
→Screen Resolution TestShow browser viewport, screen dimensions, and device pixel ratio.
→Data Transfer Time CalculatorEstimate ideal transfer time from data size and an entered link rate.
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