Shiny Mew is appearing for the first time in Pokémon Go during the Go Tour: Kanto event, but it won’t just be popping up in the wild.
In order to encounter the special Psychic-type, you will need to earn it by completing some of the event’s special research. Specifically, you will need to complete all our pages of the “All-in-One 151” Masterwork Research to get a Shiny Mew. But as a bonus, the encounter is static, meaning you will always encounter Shiny Mew when you finish the tasks, nothing is up to chance.
Because some of the Masterwork Research tasks are extremely taxing, such as needing to send 151 Gifts to friends and make 151 Great Throws on just the first page, Niantic hasn’t limited it to just the Kanto Tour on Feb. 20.
There is no deadline on finishing the Masterwork or Special Research as long as players acquire it during the event by being active. Some of the tasks are easier to do with the event bonuses, so it is best if you get as much done during the Kanto Tour and following Kanto Celebration event as possible.