Pokemon GO Invite to Raid details have begun to roll out as Niantic allows more and more players to invite friends to raid battles remotely. As of writing, this feature is only available to trainers level two or higher while Niantic does stability testing.
Previously players could only only participate in raids in person, although now only one player actually needs to be at the location of the raid for others to participate. The maximum number of raid participants has also been increased, with a maximum of five in person and an additional five online players.
Pokemon GO Invite to Raid Details: How to Invite Friends
For players that have access to the feature, all you have to do is join a lobby, public or private, tap invite friends on the right of your screen, and pick up to five friends to come to the raid with you.
The invited players will receive a notification, either if they're in game or have push notifications turned on for raid invitations. If there are other players in the lobby, they can still participate in the raid if you leave. If you are the only player in the lobby and leave after inviting a friend, they will be unable to join the lobby through your invitation.
Players can also join raids remotely without an invite using a Remote Raid Pass, which can be purchased in the in game store for 100 coins each or 250 coins for three.