The iPhone 8 supports up to 29 watts of fast charging power.
Mainly support PD protocol USB-C power adapter, can be used.
However, Apple limited the charging power of the USB-C To Lighting data cable in the system after iOS11.3, because the system no longer supports other brands of data cables without Apple's official certification. Therefore, you must go To Apple's official website or other e-commerce channels to buy Apple's official USB-C To Lighting data cable, in order to normally play the power of 29W or higher power power adapter when charging.
All in all, if you want To achieve the official 30 minutes to 50% charging power, you need an official or third-party brand of 29W and above power adapter, and with Apple's official USB-C To Lighting data cable, can be used normally.
Of course, you can also choose the iPad 10W or 12W power adapter to charge the iPhone, the actual charging speed and 29W and above power of the power adapter in the charging speed is almost the same (using 29W and above power of the power adapter to charge the iPhone, in fact, will be limited to about 18W charging power)! And the price is cheap and economical!!