http://www.techradar.com/news/pokemon-go-will-soon-stop-working-on-your-iphone-5-or-iphone-5c

Pokémon Go fans using older Apple devices will soon find that their version of Pokémon Go will soon stop, well, going, thanks to an impending update.

According to Niantic, an update to the game rolling out on February 28 will mean that Apple devices not able to support iOS 11 will be unable to cope with the upcoming improvements.