How to Watch the 'Harry Potter' 20th Anniversary Reunion Special Online

The cast of the Harry Potter film franchise is set to return for a one-off special, titled "Harry Potter 20th Anniversary: Return to Hogwarts", which airs on New Year's Day.

Celebrating 20 years since the release of the series' first film Harry Potter and the Philosopher's Stone, the cast will reminisce about their favorite moments in the magical world.

The reunion will see the original trio Daniel Radcliffe, Emma Watson and Rupert Grint return, as well as many other original cast members. They will revisit the film's old sets and reflect on their time making the iconic movies.

Here is everything you need to know about the special—including who will be part of it, and where you can watch it online.

How to watch Harry Potter 20th Anniversary: Return to Hogwarts online

The Harry Potter 20th Anniversary special is a HBO Max production, which means it will be available exclusively on the streaming service in the U.S. on Sunday, January 1.

HBO released a first-look trailer for the special on Monday that gave fans a glimpse at the jaw-dropping sets the cast will reunite in.

In the teaser clip, Radcliffe reflected: "The thing that scared me most was the implication that the most meaningful thing in our life was done. And there's something so joyous about seeing everyone and being like, 'It wasn't, though.'"

Grint also spoke with Watson about the "strong bond we'll always have," saying they're "family" and "will always be part of each other's lives."

Who will appear in Harry Potter 20th Anniversary: Return to Hogwarts?

Radcliffe, Watson and Grint may be the stars of the show, as they were in the original film franchise, but they're not the only ones who will appear in the reunion.

The trio will be joined by their former co-stars who played fellow Hogwarts pupils: Tom Felton, Oliver Phelps, James Phelps, Alfred Enoch, Bonnie Wright, Evanna Lynch, Matthew Lewis.

Of the cast members who played Hogwarts professors, family, and villains, Helena Bonham Carter, Robbie Coltrane, Ralph Fiennes, Gary Oldman, Jason Isaacs, Imelda Staunton, Mark Williams, Ian Hart, and Toby Jones will also appear.

The film franchise's directors Chris Columbus (who made films 1 and 2), Alfonso Cuarón (3), Mike Newell (4) and David Yates (5 to 8) will also take part, as well as producer David Heyman.

It is currently unclear if original author J.K. Rowling will make an appearance in the special, though given recent controversy over comments she has made about transgender women it seems this might be reason enough for her not to take part.

Harry Potter 20th Anniversary: Return to Hogwarts will air on HBO Max on Sunday, January 1, and all 8 films are available to watch on the streaming platform now.

Harry Potter
The cast of the "Harry Potter" film franchise will reunite for "Harry Potter 20th Anniversary: Return to Hogwarts", which will air on HBO Max on Sunday, January 1. HBO