If you've caught a million Pidgeys and Rattatas looking for Ditto, good news. The Pokemon Go 0.49.1 update for Android and the 1.19.1 update for iOS devices brought a new time-saving feature that allows you to transfer multiple Pokemon to Professor Willow. You can get rid of all those useless Pokemon and rake in the candy with just a few taps of your finger.
Before you try the mass transfer tool, I need to warn you. It is just way too easy to accidentally transfer a Pokemon with this tool and you don't want to lose that hard-earned Gyarados. Go to your Pokemon and favorite every one that you don't want to transfer. The tool won't work on Pokemon that are favorited. Pokemon assigned to gyms and your Buddy Pokemon are also safe.
Make it rain candy
OK, now that your best Pokemon are safe, you can now wield the power of the mass transfer tool. Go to your Pokemon screen and press your finger on one of the Pokemon you want to transfer. That Pokemon will become surrounded with a green square. This lets you know that you're in select mode. Scroll through your Pokemon and tap on all the others that you want to transfer.
When you're done, tap on the Transfer button at the bottom of the screen. All of your Pokemon will be given to Professor Willow and you'll get a candy for each of the Pokemon you transferred.