How does USB port on a power strip detect the optimal current output?

I am looking to buy a power strip with USB ports and came across this one online. The description says "Top-notch USB smart charging technology which can detect and deliver optimal current output up to 2.4A per port." So when I charge my iPhone 6s which requires input current of 1A, the USB port will deliver exactly 1A?

• deliver optimal current output up to 2.4A ..... it means that it will hold the output voltage at 5V as long as you do not draw more than 2.4A ..... if you draw more current, then the voltage will start dropping or the output will shut down or the charger will start smoking – jsotola Jan 10 at 3:31
• In other words, it's a USB power strip that does nothing more than adhere to USB specs. Oh, the frabjous joy! – TimWescott Jan 10 at 3:50

I am looking to buy a power strip with USB ports and came across this one online. The description says "Top-notch USB smart charging technology which can detect and deliver optimal current output up to 2.4A per port." So when I charge my iPhone 6s which requires input current of 1A, the USB port will deliver exactly 1A?

Likely this is a knockoff(not necessarily bad) of adaptive fast charge technology, which allows some phones to draw current at more than 5V from compatible chargers under the USB Power Delivery spec (Which amusingly allows for up to 5A@20V under USB 3). Given the product claim phrasing I would expect "smart behavior", specifically identification of devices that have fast charging options and the delivery of appropriate voltage to them (1.6A@9V for example for Samsung AFC).

As far as the exact amount of current drawn, these are voltage supplies, not current supplies, so the power supply provides a solid 5V(Or hopefully other voltages) at up to 2.4A, but it is the device charging that determines the actual current draw, which will vary across the charge cycle and also depending on additional load. If you put the volume on full and run a 3D game on your smartphone while it's charging the incoming power will supply the phone first and only the surplus will make it to the battery. In this situation the current draw would be high even if the battery was in top up or trickle charging phase.

The USB port is probably not current limited. Most of the time, it is the load and not the current that determines the current. So, "optimal current output up to 2.4A" means "the port should provide 5V at up to 2.4A of current" Above 2.4A, I would expect the voltage to drop or possible start generating too much heat.