18 w。
The iPhoneX Fast Charge uses the USB PD charging protocol, and Apple is one of the members of the charging protocol alliance.
At this stage, Apple's official chargers that can be used by the iPhoneX to support fast charging have five USB-C interfaces: Apple 18W, 29W, 30W, 61W and 87W
The original Apple x charger is 18w. According to the official introduction, it can be charged up to 50% power in 30 minutes, requiring the use of 18W or more power adapters (need to be purchased separately).
Apple x ordinary charging is 5w, support 18w fast charge.