Reverse wireless charging, which Samsung calls Wireless PowerShare, is one of those features that sounds gimmicky until you actually need it. Basically, it turns the back of your Galaxy S25 Ultra into a wireless charging pad.
The most common way people use this is for their Galaxy Buds. You're heading out, realize your earbuds are dead, and just plop the case on the back of your phone for 10 minutes while you get ready. Problem solved.
To turn it on, you can either dig into Settings > Battery and device care, or just pull down your quick settings and tap the Wireless PowerShare icon. Once it's enabled, place any Qi-compatible device on the back of your phone and charging starts automatically.
It works with pretty much anything that charges wirelessly. Galaxy Watch, AirPods, other phones, any Qi earbuds. People use it to give a friend's dying phone enough juice to call an Uber. Not efficient, but it works.
A few things to know: It's going to drain your battery faster than just using your phone normally, so make sure you've got charge to spare. The phone is smart enough to automatically stop sharing power if your own battery gets too low. And the charging speed is nothing special. We're talking emergency top-ups, not full charges.
Where this really shines is when you're traveling. Instead of packing a separate charger for your earbuds and watch, you can just use your phone. One less thing in your bag.
Is it something you'll use every day? Probably not. Is it handy to have when you need it? Absolutely.