I've been shopping in Mercari since 2020, at first I was skeptical because the only selling site I knew was Ebay, so I got all the information possible, like what are the rules, how refund works if something goes wrong? Is there buyers protection? And yes so you have 3 days once you receive an item to inform them if there is any issue with your order. I usually buy items new or like new condition, and just to be sure I double check with the seller so there is no unexpected surprises. All my transactions have been smooth, you have to be careful who you buy from, check their rating, and reviews from others but I totally recommend Mercari 100%