How to share a Strava activity by tagging a friend:
On the Strava app, you can invite a friend who was with you but didn't record their activity. You can invite friends regardless of whether they're already on Strava. First, open the activity you would like to tag your friend in. From the activity details page, you can select the Add Friend button. Select the application you would like to use to send your share invitation. The friend will receive the link to the invitation through whichever app you chose to use (email, text message, etc.) The friend can then accept the invitation, or if they are not on Strava, they can create a new account. The activity will appear on your friend's Strava profile and feed as if it was their own. Learn more about tagging your friends on iOS and Android.