Is this adapter cable compatible with Thunderbolt 3 devices?

Yes, the StarTech.com USB-C to DisplayPort adapter cable is compatible with Thunderbolt 3 devices.

What resolutions does the StarTech.com USB-C to DisplayPort adapter cable support?

The adapter cable supports resolutions up to 7680×4320 (Ultra HD 8K) at 30Hz, and is also backward compatible with 4K and 1080p resolutions.

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StarTech.com CDP2DP146B 5.9 ft (1.8 m) - USB-C to DisplayPort Adapter Cable - 8K 30Hz - HBR3 - USB-C Adapter - Thunderbolt 3 Compatible

With 4x the resolution of 4K this 8K USB C to DisplayPort 1.4 cable delivers the stunning quality of UHD, supporting resolutions up to 7680×4320.
Experience high bandwidth connections up to 32.4Gbps w/ this HBR3 8K DisplayPort cable.
The USB C to DP video cable is backward compatible with 4K and 1080p, making it a great accessory for your home or office while future-proofing for 8K.
Enjoy the convenience of connecting your USB Type C device to your DP monitor with this DisplayPort cable.