TikTok, already a fixture on many smartphones, is moving to the biggest screen in the home: the television set.

This week, Amazon.com Inc. launched the app on its Fire TV streaming-TV devices, introducing TikTok to its audience across the U.S. and Canada. The collaboration enables users to watch TikTok videos with family members without “huddling around a cellphone to see the latest viral video,” Amazon said in a blog post.

TV...

TikTok, already a fixture on many smartphones, is moving to the biggest screen in the home: the television set.

This week, Amazon.com Inc. launched the app on its Fire TV streaming-TV devices, introducing TikTok to its audience across the U.S. and Canada. The collaboration enables users to watch TikTok videos with family members without “huddling around a cellphone to see the latest viral video,” Amazon said in a blog post.

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TV screens stand to present a tremendous opportunity for TikTok, even as it already claims more than one billion monthly users. While the living-room experience might not appeal to its most avid current users, the ByteDance-owned platform says a more communal TikTok could appeal to families. Perhaps it could help it reach people who have previously shied away.

But in making the jump from hand-held touch screens to a big screen in the center of the living room, much of what makes the app unexpected and fun is lost. A lot of what feels natural about TikTok on mobile devices looks and feels bizarre on a hulking TV screen operated by a remote control.

Here are the challenges:

TVs aren’t vertical

TikTok’s vertical videos are formatted to be viewed on smartphones, where they can take up most of the screen. They look fine on a larger screen, because smartphone cameras have really improved over the past few years. It’s just that TV screens—with the rare exception, such as Samsung’s rotating-screen Sero—are fixed in horizontal orientation. The shape of a vertical video leaves sizable voids on each side. TikTok’s TV app fills them in with a blurry color effect that matches the video that’s playing.

The scroll is gone

TikTok is native to smartphones and arguably rose to popularity for that reason. It is most popular among teens and 20-somethings, who get lost in the seemingly endless scroll of short-form videos.

On the Fire TV app, skimming through TikTok videos feels a lot like flipping through channels. To go to the next video, you click on the left side of the navigation button on the Fire TV Stick remote—a gesture that waters down the soft thrill of swiping up to discover new content. There’s also no search bar on the app, making it hard to find your favorite creators and search specific hashtags.

You can’t comment

The comment section on TikTok has a culture of its own. It’s where users react with memes and emojis. It’s where people go to add context to videos by ranting, raving and criticizing. It’s how people tag friends and how influencers engage with their audiences. Comments are central to being active on TikTok.

On TV, the comment section becomes a spectator sport. You can read comments left by other people. You can even like them, but you can’t share your thoughts or click on profiles belonging to commenters.

You also can’t access your inbox to check your DMs. And you won’t see your notifications, so you won’t know who reacted to your posts, or who followed you unless you check your smartphone.

You can’t contribute

TikTok’s mobile app houses a number of tools enabling users to make creative social videos, as long as three minutes each, to share across the internet. The TikTok TV app doesn’t allow you to do any of that.

You also can’t shoot new content or edit existing content on a TV, nor can you upload video via the TV app. You can’t go live as a creator—or even view live content—further limiting how people typically socialize on TikTok.

What’s TikTok? What’s a TikTok meme? How do you make a viral TikTok—aka a banger? WSJ’s Joanna Stern set out to get answers to the questions about the social-media app, and danced along the way. The Wall Street Journal Interactive Edition

It’s less personal

TikTok’s algorithm curates a video feed that feels highly personalized to you. Though not without controversy of its own, the algorithm is the company’s secret sauce that keeps users coming back. The TikTok Fire TV app shows liked and suggested videos for account holders who are logged in. That means anyone who does sign in for a more curated experience risks sharing their TikTok guilty pleasures with the whole household. Users can, however, stream TikTok content on their TV without creating an account, just as they can on smartphones.

“The big screen experience allows families and friends to enjoy TikTok as part of their daily or weekly routine together, complementary to their weekly TV viewing experience,” a TikTok spokesman said in a written statement.

Neither TikTok nor Amazon would say whether user data is shared through the joint effort, or whether either company paid the other in the deal.

Daniel Rausch,

Amazon’s vice president of entertainment devices and services, said the app will likely evolve over time to include more features. “You’ll see us continue to add and build with the momentum we see from customers going forward,” he said.

Amazon’s Fire TV app is the first to roll out in the U.S. But more TV apps are expected to be launched in coming weeks, the TikTok spokesman said.

Write to Dalvin Brown at dalvin.brown@wsj.com