J.K. Rowling’s Pottermore website allows fans of her bestselling book series to learn the answers to several questions that mere Muggles could once only speculate about, like what Hogwarts house they’d be sorted into and what type of wand would choose them in Ollivander’s shop.

And today, the site is equipped to answer another question that Potter fans have long pondered: what form their Patronus would take.

As Remus Lupin tells Harry in “Prisoner of Azkaban," a Patronus is “a guardian which acts as a shield between you and the Dementor,” a dark creature that feeds upon human happiness.

A Patronus takes the form of an animal that reflects the spell caster. Harry’s is a stag like his father’s, while Severus Snape’s was famously a doe, the same Patronus cast by the woman he loved, Harry’s mother.

To discover your own Patronus, visit Pottermore.com/Patronus for a 3-D experience that features questions and prompts written by Rowling herself. The quiz is multiple choice but time-sensitive, encouraging users to trust their gut and answer immediately. Don’t respond fast enough, and the question will fade away.

While the majority of Patronuses take the form of creatures that exist in the Muggle animal kingdom — including dolphins, eagles, rabbits and aardvarks — a lucky few will learn that their Patronuses take the form of magical creatures like unicorns and hippogriffs, which Rowling noted on Twitter is “rare.”

Don’t think your Patronus is a good fit? Keep in mind that it can change. In the “Deathly Hallows,” we learned that Nymphadora Tonks’ Patronus changed to a wolf after she fell in love with Lupin, a werewolf.

“Based on the fact that Patronuses are conjured by recalling happy memories, it stands to reason that a Patronus might change its form after one falls in love, and the memories used to conjure the Patronus largely revolve around the person the caster is in love with,” reads the Harry Potter Wiki.

In fact, Rowling herself tweeted today that her own Patronus has changed with time.

If you want to take the quiz a second time though, you’ll have to create a second Pottermore account, but Houston-based writer Melissa Veres — who got a red squirrel the first time she took the quiz — says it’s worth the trouble to find the perfect Patronus.

“A red squirrel didn't feel like it fit,” she said. “What do squirrels do? They hoard nuts and cause cars to swerve. Maybe you can argue it’s a utilitarian option, someone who prepares and works hard, but it didn't feel like it connected to me. And, as a serious Harry Potter fan, these things clearly matter. Plus, when taking the first quiz, I missed answering a few questions due to buffering and child distractions. I wanted a chance to retake the quiz in full, and give it a real go.”

Veres’ new Patronus? A black swan — a Patronus she’s very happy with.

Share your own Patronus on social media with #ExpectoPatronum.