There are a few things you can do with your old smartphone when it's time to buy a new one.
Without a doubt, the best option is to sell it and use that money to offset the cost of your new phone.
You could sell your phone directly to someone else on online marketplaces like eBay or Craigslist, in which case you'll know your old phone went right to someone else's hands.
Another popular option is to sell your old phone to trade-in sites or back to your carrier.
Usually, if your old phone is in pretty good condition, trade-in companies or carriers can sell it right back on their websites without much refurbishment.
If your phone is old, or it's taken a few bumps and scratches over the years, trade-in companies and carriers are less interested. They'll buy it anyway, but they'll sell it on to companies who can make better use of phones in "OK" condition.
Check out what happens to your old phone once you sell it on trade-in sites or back to your carrier:
