It’s time for a lesson in Wedding Etiquette: The Social Media Edition. Because according to a recent survey, only 2 out of 5 wedding guests say that social media was encouraged, and they were even given specific Twitter hashtags to create a real-time feed that everybody could follow. And most Twitter users say they tweeted about a wedding while they were there.

But one-third of wedding guests were also asked not to use a camera or mobile device during the ceremony, because the couple wanted the only photos posted to be the official photos. Guests were also asked not to tweet or Facebook anything before the wedding. That way, they wouldn’t accidentally reveal any surprises. Like one couple we read about who were upset when a bridesmaid posted a picture of the bride getting ready, and the groom saw his wife-to-be in her dress before he saw her in person. 

So, when is it cool to tweet and post pictures from a wedding? In general, etiquette experts say it’s important to ask the couple’s permission before posting any photos of a wedding or reception online, or at least to wait until the couple shares the first photos.

And if you’re planning a wedding, make sure all your guests know beforehand what’s okay to post and tweet, and what’s not. People are usually willing to follow the rules if they know what the rules are.