Can I use USB-C to charge my GS9?

[Poweranimals]

Since it's not an official Samsung charger I didn't want to take any chances. Also, is it capable of fast charging?

 

[Hadron]

USB-C is just a connector type, so without knowing the specs of the charger we can't say whether it will fast charge your GS9 or not.

But we have 3 USB-C handsets in my family (a HTC 10, a Pixel 2 and a Galaxy S8), and use their chargers interchangeably between the devices. Not all will fast charge with different chargers, but as none is some cheap, poor quality charger I've never worried about damage. We've also used older chargers with a USB-A to USB-C cable, which of course will not fast charge but will still charge the phone.

In short, we don't have enough information to answer the question, but it's certainly not the case that you have to use a Samsung charger with a Samsung phone. I might have some reservations about some cheap, unbranded charger of unknown quality, but any reputable phone charger I wouldn't worry about (for example we have a couple of Ankers in addition to OEM chargers, and these work fine). I'd do a bit of research before I connected my laptop's charger to my phone though .

Of course all of that assumes that you are talking about a charger. If you mean just a USB-C lead connected to a computer, no problem at all: it won't fast charge, but it will charge the phone.