What cable and charger do I need to get the fastest charge speed on my Samsung Galaxy S8? The Samsung Galaxy S8 comes with the USB Type-C connector. I noticed that the USB-A Male to USB Type-C Male cables that are being sold often have a USB Specification associated with them. The Amazon Basics cables, for example, come in 2.0 and 3.1. Is the 3.1 specification cable required to get the fastest charging speed? Or will the 2.0 cable provide the same speed?

Also, there have been many fast charging specifications like QuickCharge 2.0, 3.0, 4.0. Which quick charge specification and version does the Galaxy S8 actually use for the fastest charge?  And is it compatible with older specifications like QC2.0?
Which Galaxy S8 do you have? 

The version with a Qualcomm Snapdragon supports QuickCharge 4, which is backwards compatible. 

For the cable choice, QuickCharge 3 used 2.5A on 5V to charge. So your cable and charged need to support that amperage. What QuickCharge 4 uses is unknown so far.

In order to achieve the maximum you need usb 3 with a type C connector (specified for 3A). However many manufacturers sell usb 2 charger with 2A or even more, including Samsung with their fastcharge. The cable itself does not really matter, however, to be save buy a 3 or 3.1 cable, since those were built for 3A of power.