Prince Harry and Meghan Markle aren't the only newlyweds who said "no, thanks" to the traditional wedding gift of a mixer or knife set. Like the new Duke and Duchess of Sussex, more couples are opting to set up a charity registry when celebrating their big day.

The use of charity registries is up over 230 percent from last year, according to The Knot's annual Wedding Registry Study. About one in 10 couples incorporated some type of charitable gifting into their wedding registries last year, according to survey of over 6,600 engaged or recently married couples.

"When we look at this next generation of people getting married, be it millennials or Gen-Z, we know that they're much more socially conscious. So when they think about their wedding registry, they think, 'Why not give back to charities that mean something to me?'" The Knot's Editor-in-Chief, Kristen Maxwell Cooper, tells CNBC Make It.

Couples are now also a little older when they get married on average and may have already lived together. So when it comes to the material things, they may want to upgrade a few items, but then they also start to think about incorporating a charity that is "near and dear to their heart," Cooper says.

Forgoing gifts can do real good. The Knot found that couples can bring in, on average, $338 in donations.

Cooper recommends explaining a bit about the organizations you choose and why you selected them. "Give a little more context around why you chose this charity and why it's important to you," she says.

For example, when they were planning their wedding, Prince Harry and Markle personally selected seven charities, including the children's HIV association CHIVA, a cause that was supported by Prince Harry's late mother Princess Diana of Wales.

You can also combine a charity registry with a more traditional one. Most couples actually opt to set up an average of three, the Knot's survey found, with the average wedding registry containing 125 items valued at $4,853.

While charity registries are on the rise, traditional retail registries are still the most popular option. Over eight out of 10 couples register for one of these, with Bed, Bath & Beyond topping the list of most popular retailers.

If you're attending a wedding this year and you can't find the gift registry, a safe bet is something for the kitchen. Bake-ware, cookware and appliances are the most sought-after presents, according to The Knot.

If there a registry, Cooper says, it's better to stick to it: "There's this idea that it's impersonal to buy off the registry, when really, it's exactly what the couple wants."

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