Small pro tip: iPhones like the X, XS and XS Max, beep, then beep again, to indicate fast-charging mode is on.
This happens when you are using an Apple USB-C-to-Lightning cable and a charger that supports USB-C PD (Power Delivery).
Then your iPhone will go from 0-50% in about 30 minutes. After which it will charge slower for safety reasons.
You can use the Apple USB-C chargers that come with MacBooks or MacBook Pros (also sold separately), but there are also third-party chargers that work with fast-charging.
Someone asked me what non-Apple chargers support this. Pictured here are some non-Apple chargers I use, that support iPhone fast-charging. They are from Innergie, Energea and Anker.
Don’t use non-MFI certified USB-C-to-Lightning cables. The cable must always be an Apple USB-C-to-Lightning cable, which comes in 1m or 2m lengths.
Currently there are no third-party USB-C to Lightning cables which are MFI-certified by Apple yet, but that may change down the road.