Hello we are arriving on Friday and we want to buy from the app navigo card one day before but we will use it o friday. will it be valid on friday ? thank you
With Navigo Day passes, you can choose which day it is valid, up to 6-days in advance. So, yes, you can potentially buy a Navigo Day pass on a Thursday and set it's valid/active day to be Friday.
Regarding buying a Navigo Day pass on your phone and using Navigo Day pass from your phone without the physical card, only recent-model Samsung Android phones currently support this functionality. This is the list of Samsung phones supporting Navigo Day Passes on the phone itself.
The Bonjour RATP app and Ile-de-France Mobilités phone app do not support Navigo pass on any Google Pixel phone nor any iPhones as of May 2023.
Note that you may be asked to create / have a Ile-de-France Mobilites Connect account to buy and use Navigo from your phone (without the physical card).