Do I need internet connection to enter the stadium with a mobile ticket?

An internet connection is required to download the ticket(s) when you first receive them. Then on match day, after your tickets have been automatically activated (i.e.: after 11:30 BST), you will need to open the UEFA Mobile Tickets app and connect to the internet just once so you can load your match ticket with the QR code revealed.

You will also need your phone to be charged and have Bluetooth on.