But other than the blow your bank balance takes to watch someone exchange vows, for some, the most important question is what to wear.
The general rule is don't wear white - but what about off white? Or cream? What about patterns?
These are the questions plaguing the internet after one woman posted a photo of a dress on Reddit and made the mistake of asking advice.
Reddit user honeycomehome posted the thread, asking simply: "Is this dress too white to wear as a guest to a wedding?"
The general consensus was the dress would be perfectly acceptable.
"I think it's a nice dress. I see it as a floral dress rather than a white dress. You could also wear it with flats or pretty sandals to make it look a little less formal if needed," OrangeBeatch wrote.
"Not at all. This whole 'no white, not even a thread' thing is so out of hand. Its like people are inventing sh*t to get upset about. It's really silly. That dress is appropriate unless the event is black tie."
And then this woman, who speaks for all of us: "I see that stuff and I secretly think, 'Wow, I wish my life was so free of adversity that just seeing some white fabric on a guest at my wedding would be the worst thing that's ever happened to me!' Hahaha. Btw, your dress sounds gorgeous."
It's an older thread that has recirculated online this week, so we can only assume she figured out what to wear in the end.