When you join Wedding Party as a guest, you'll first be prompted to set up your user account with an email address and password, or with Facebook. After this, you'll be prompted to enter in the "Wedding Key" of the event you're trying to join.
You must type in the exact Wedding Key of the event you're trying to join. If you try to "search" for the wedding you want to join instead of typing in the exact Wedding Key of the event, you might join a stranger's wedding if their Wedding Key matches what you typed. This is because the Wedding Key is just like a code -- it has to be exact.
For example, if Billy and Linda Smith set up their event and their Wedding Key is "billlinda2017", you have to type in that exact code -- typing in something like "billyandlinda" or "smithwedding" might join you to someone else's event if that's their Wedding Key.
Remove yourself from a wrong wedding on an iOS device:
There are two different places where you can prevent yourself from joining the wrong wedding. The first is after you type in the Wedding Key of a stranger's wedding. You should see an option to cancel and not join that wedding in the top right corner if you recognize right away that you've got the wrong people.
If you've pressed "Get Started" and then realized that you've got the wrong couple, you can still remove yourself from their wedding.
1) First, find the "Notifications" button at the top right corner of their photo timeline (which looks like a bell). Press that, and a menu should slide out with their wedding event notifications.
2) There should be a red "Leave Wedding" button on the bottom right corner. Press this button to remove yourself from the wedding.
Remove yourself from a wrong wedding on the web:
1) Login to Wedding Party on a computer here. Use the same email address and password you used to login and join the wrong wedding previously.
2) You'll be directed to a page that shows the weddings you are a part of. Click the "X" symbol in the top right corner of the wedding you'd like to leave.
3) Click "Ok" in the popup to confirm your removal from the wedding. After that, you will be removed.
4) If you know the correct Wedding Key of the wedding you'd like to join, click the black "Join Wedding" button on the page to get added to the correct wedding.
If you have joined the wrong wedding on Android, you can use a computer and complete the steps above to remove your user account from that wedding. There is currently no way on an Android phone to remove yourself from a wedding