XL Candy is a special type of candy in Pokemon Go that allows players to level up their Pokemon beyond level 40, all the way to level 50. Here are some ways to obtain XL Candy:

• Catching Pokemon: Catching wild evolved forms of Pokemon guarantees XL Candy, while catching basic Pokemon may or may not provide XL Candy.
• Transferring Pokemon: When transferring Pokemon, there is a chance for it to leave behind an XL Candy with its regular Candy.
• Raids: Pokemon caught in raids will guarantee an XL Candy.
• Hatching Eggs: The number of XL Candy received will be higher when hatching eggs that require more walking.
• Trading Pokemon: Sometimes, when trading Pokemon with another player, you will earn an XL Candy.
• Walking Buddies: When walking your Buddy Pokemon, you will earn Candy dependent on its species per a certain number of km. Occasionally, you may collect an XL Candy alongside the regular Candy.
• Conversion Exchange: When opening up the options.

It is important to note that XL Candy is Pokemon-specific and cannot be used on other Pokemon species.