TechCrunch first reported the existence of the port last month. "The port has a 6-dot brass contact array inside the groove for the ‘bottom’ strap connector slot. Several sources have confirmed its existence and placement to me. It is very similar to the connector for the Lightning connector in iPhones, as that connector currently only uses 6 of its 8 available pins."
The port will likely be used by Apple to run diagnostics and perform repairs on the smartwatch. It's been suggested that perhaps one day we could see some smart accessories or bands that make use of it but thus far Apple hasn't even acknowledged that it exists. Additionally, Louis noted that retail staff haven't had any training on how to use the port.
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