Pokemon Go has introduced a new way to evolve some Pokemon. Just as in the mainline series, you can now evolve certain Pokemon by trading them to a friend. However, this works a little differently than it does in a traditional Pokemon game, so we've put together this explainer detailing how to evolve Pokemon through trading in Go.
How To Evolve Pokemon By Trading
In mainline Pokemon games, a handful of monsters can only be evolved by trading them to another player, but in Pokemon Go, these creatures could be evolved the same way as most other Pokemon: by feeding them a set amount of Candy. Now, however, there's an alternate method of evolving them: if you receive an eligible Pokemon through a trade, its Candy requirement will be completely removed, essentially allowing you to evolve it for free.
While this new evolution method has only been recently added to Pokemon Go, it retroactively applies to past traded Pokemon. That means if you've previously received one of the eligible Pokemon through a trade, its Candy requirement to evolve will also be removed.
Which Pokemon Evolve By Trading?
The new trade evolution method applies to the same Pokemon that evolve by trading in the mainline games:
In the main series, a handful of other Pokemon--such as Scyther and Onix--also evolve by trading if they're holding certain items, but their evolution method in Pokemon Go has not been changed, so you cannot trade for a Scyther and then evolve it into Scizor without spending any Candy; only the Pokemon listed above will have their Candy requirement removed if obtained through a trade.
Boldore, Gurdurr, Karrablast, and Shelmet are among the newest Gen 5 Pokemon to arrive in the game. However, a handful of other Gen 5 Pokemon can only evolve using a new item called the Unova Stone. You can read more about how to obtain one of those and which Pokemon it works on in our Unova Stone guide.