SYDNEY, Australia — The lights were dimmed, the crowd was masked, and plexiglass divided the orchestra.

Jemma Rix, draped in royal blue and holding a sanitized scepter as Elsa, emerged to greet the “Frozen” family — her spunky sister, Anna, the dashing Prince Hans and the stoic reindeer Sven — all tested for Covid-19, belting out familiar lines with new meaning.

“For the first time in forever,” they sang, “nothing’s in my waaaay!”

The crowd erupted in applause, not just for the cast, but for the moment: Actors are back onstage, and audiences are back in seats. At a time when New York and London theaters remain dark, Australia’s stages are (carefully) bright — “Come From Away” and “Harry Potter and the Cursed Child” have reopened in Melbourne, “Hamilton” is scheduled to join “Frozen” next month in Sydney, and “Moulin Rouge! The Musical” is preparing for a summer start in Melbourne.

Australia, normally a secondary market for big-brand shows developed in New York and London, has become an unexpected pandemic pioneer: a model and a test case for the global theater industry. Now producers on Broadway and the West End are watching the Australian rebound with envy, hope and a desire to learn what works as a kneecapped art form tries to get back on its feet.

“It’s like living in the future,” said Thomas Schumacher, the president of Disney Theatrical Productions, who spent six weeks in Sydney — two of them quarantined in a hotel room — to cheer on the “Frozen” opening. Disney is planning to open 24 stage productions on four continents this year, including “The Lion King” and “Aladdin” on Broadway, and Schumacher is looking to Australia as a harbinger.

Much has changed. Actors are greeted at some theaters by robots that take their temperatures. Patrons must scan QR codes as they register for contact tracing upon arrival, and they are admitted at staggered times so they can be seated by row. After the final ovations, actors skip the familiar stage door selfie sessions with fans.

But the visceral thrill of live theater is back. The “Hamilton” producer Jeffrey Seller, now in quarantine in Sydney as he awaits clearance to visit his show in rehearsal, is giddy at the prospect of seeing actors onstage; he is hoping Australia will be the first of seven “Hamilton” productions to open this year.

“I feel like Dorothy going to Oz,” he said. “Finally the whole world is in full color again.”

Australia has been far more successful at containing the virus than either the United States or Britain, mostly because it adopted strict safety protocols and people have followed public health advice. The differences are stark: Over the past week, Australia has averaged fewer than one daily case per 100,000 people, according to a New York Times database, while Britain has averaged 15 and the United States 21. The raw numbers are even starker: Australia averaged a total of only six new coronavirus cases a day over the past week, while the United States averaged 69,483.

Now British and American producers are stuck waiting for vaccines to be rolled out in their countries. In the West End, some shows are hoping to reopen in the spring, and on Broadway, fall seems more likely — while in Australia, shows were able to open long before anyone was vaccinated.

The biggest lesson so far has been positive: Ticket sales are strong, suggesting that theater lovers are eager to return, and willing to spend money. “There’s a lot of pent-up demand,” said Carmen Pavlovic, the lead producer of “Moulin Rouge!,” “and it bodes extremely well.”

The early success is attracting more productions. The producers of “Jagged Little Pill,” a musical built around the songs of Alanis Morissette, which had run only a few months on Broadway before the shutdown, said they now have Australia in their sights as they plan their first international production.

The momentum has been building since Australia’s theater industry began lobbying for a return back in June. Some productions got government incentives to reopen, and the industry created its own nationwide coronavirus safety plan with epidemiologists to persuade officials that theaters, as a whole, would not make the pandemic worse.

Onstage, the action is unchanged by the pandemic. In “Come From Away,” stranded air passengers still take turns kissing a cod.

And in “Frozen,” Elsa still manages to conjure an ice palace during “Let It Go,” although that one unexpectedly took some extra engineering after the theater reconfigured its air conditioning system as a virus control measure. Surprise! Increased air exchange wreaks havoc with stage fog. The special effect had to be recalibrated.

Offstage, however, it’s a cautious new world.

The first step: separating buildings into zones — one for cast and crew, and another for the audience and anyone who deals with them.

At several theaters — including the Princess in Melbourne, where “Cursed Child” just restarted on Thursday — “transition zone” hygiene stations offer sanitizer, gloves, masks and paper booties for those venturing backstage. And at “Hamilton” rehearsals, performers carry tubes of “Hamiltizer” to disinfect their hands as needed.

“We’re in a space that’s privileged,” said Matu Ngaropo, who is playing George Washington. “We don’t take that lightly.”

The “Frozen” cast is divided in two for their preshow warm-up, making it harder for pitch and rhythm to coalesce, but reducing the spread of aerosols.

“You can’t hug each other, you can’t touch,” said Matt Lee, who plays the lovable snowman Olaf. “You have to be comfortable with eye contact.”

Instead of an encouraging hand on the shoulder between scenes, Mr. Lee and Ms. Rix flash each other a peace sign.

“Even my dresser,” Ms. Rix said. “I see her all the time, but I don’t even know what she looks like because she’s always got a mask on.”

Microphones are disinfected with ultraviolet light; pens and flashlights are sanitized after use. Usher uniforms, which used to just hang on racks for anyone to grab willy nilly, are organized with military precision: each in a bag with a name tag right above.

The first productions to open here last fall felt awkward, as government guidelines required four square meters per person, leaving many seats empty. Now some theaters in Sydney and Melbourne can fill up to 85 percent of their seats.

Disruptions are unsurprising. In December, a small outbreak north of Sydney prompted Disney to cancel several performances of “Frozen,” and this month a small outbreak in Melbourne led to a five-day, citywide lockdown that forced “Come From Away” to close temporarily.

“It feels like upheaval is the new normal,” said Ms. Pavlovic, who noted that her show’s casting was repeatedly complicated by changing restrictions on travel between Australian states.

The pandemic has even affected the old show-must-go-on ethos of performing through illness, which no longer makes sense in the age of a highly contagious virus, when one sick performer can easily take an entire cast out of commission. “We added two standbys to the company to make sure we were thoroughly covered if somebody got sick,” said Sue Frost, a lead producer of “Come From Away.”

Audiences are adapting, too. Producers said that last-minute purchases have become increasingly common. Even with a now-standard promise of exchanges and refunds if shows are canceled because of the pandemic, many people are wary of buying tickets (prices have stayed the same) for fear of losing their money.

At a recent weekend performance of “Frozen,” Caryl Barnes, a psychiatrist who had come to the show with her husband and two teenage daughters, said that she had bought tickets just a week earlier. Terri Kosta, standing in the lobby with his 7-year-old daughter and his wife, said that he bought his tickets the day before the show.

Outside the theater, arriving patrons didn’t seem to mind giving up their mobile phone numbers for contact tracing in the event of an outbreak. By and large, they said they were excited to return, even with scheduled arrival times that required some people to get to the theater 45 minutes early.

Inside, every few minutes there were audio reminders to wear a mask, practice good hygiene and consume food and drink only while seated. (Epidemiologists calculated there would be less risk if everyone faced forward.)

“Everybody just has to do what they have to do,” said Mr. Kosta, a builder, who noted that he’d been wearing masks at work for months. “It’s uncomfortable, but it’s worth it.”

After the final standing ovation, the crowds departed by row, as if exiting a plane.

Diana Burgess and her friend Clara Potocki, two lawyers in their 30s, lingered and laughed, standing in line to buy souvenirs, decked out for the occasion in masks with sequins.

“It’s so nice to be able to do this again,” Ms. Burgess said.

“It feels absolutely safe,” added Ms. Potocki, as she waited to purchase a stuffed Olaf. “It’s great to be out.”

Damien Cave reported from Sydney, and Michael Paulson reported from New York.