What’s the safest way to sell a mac?
Hello reader, I am preparing to sell my old MacBook Air (unsure of what apple computer I'm going to buy) and I can still sell it for around $500 USD. I'm very anxious that if I sell it, my personal info will still be on it somehow, the iMac my dad handed down to me still has his credit card info pop up every once and a while although he wiped it clean. So what is the best way to know that it is 100% clean? Also I don’t know where to sell it besides amazon and I don’t want to do a trade-in. Can someone give me advice?
MacBook Air 13", macOS 10.12