HONG KONG, April 26 (Reuters) - The content

recommendation algorithm that powers the online short video

platform TikTok has once again come under the spotlight after

the U.S. ordered its Chinese owner, ByteDance, to sell the app's

U.S. assets or face a nationwide ban.

Here is how it works and why it has attracted more

discussion than technology used by its rivals such as Meta's

Instagram, Google's YouTube and Snapchat

:

ALGORITHMS

The algorithms are deemed core to ByteDance's overall

operations, and ByteDance would rather shut down the app than

sell it, Reuters reported citing sources.

China made changes to its export laws in 2020 that give it

approval rights over any export of algorithms and source codes,

adding a layer of complexity to any effort to sell the app.

Academics and former company staff said that it is not just

the algorithms, but also how it works with the short video

format, that has made TikTok so successful globally.

IT'S THE APP TOO

Before the emergence of TikTok, many had believed that

technology connecting a user's social connections were the

secret sauce to a successful social media app, given the

popularity of Meta's Facebook and Instagram.

But TikTok showed that an algorithm, driven by the

understanding of a user's interest, could be more powerful.

Rather than building their algorithm on "social graph" like Meta

has, TikTok executives including CEO Shou Zi Chew have said that

their algorithm is based on "interest signals".

While rivals have similar interest-based algorithms, TikTok

is able to turbocharge the algorithm's effectiveness with the

short video format, said Catalina Goanta, an associate professor

at Utrecht University.

"Their recommender system is very common. But what really

distinguishes TikTok as an app is the design and the content,"

she said.

The short video format enables TikTok's algorithm to become

much more dynamic and even capable of even tracking changes in

users' preferences and interests across time, going as granular

as what a user may like during a certain period of time during

the day.

RAPID DATA COLLECTION

In addition, the short video format allows TikTok to learn

about user preferences at a much faster rate, said Jason Fung,

former head of TikTok's gaming unit.

"Because it's in bite size format, it is short video, you're

able to collect data about a user's preference a lot faster than

YouTube, where maybe the average video is just less than 10

minutes long," he said, "Imagine you're collecting data about a

user on average every 10 minutes versus every couple seconds."

And the positioning of TikTok as an app built for mobile

devices from the beginning also gave it an advantage over rival

platforms that had to adapt their interfaces from computer

screens.

TikTok's early entry into the short video market also gave

the company a big early-mover advantage. Instagram did not

launch Reels until 2020 while YouTube launched Shorts in 2021,

both of which lag TikTok in years of data and product

development experience.

ALLOWS EXPLORATION

TikTok also regularly recommends content that falls outside

of users' interest, which the company's management has

repeatedly said is essential to TikTok's user experience.

A study, which researchers from the U.S. and Germany

published last month, found TikTok's algorithm "exploits the

user interests in 30% to 50% of the recommendation videos" after

examining data from 347 TikTok users and five automated bots.

"This finding indicates that the TikTok algorithm opts to

recommend a large number of explore videos in an attempt to

either infer better the user interests or maximise user

retention by recommending many videos that are outside of the

user's (known) interests," the researchers wrote in the paper

named "TikTok and the Art of Personalization".

MOBILISES USERS INTO GROUPS

Ari Lightman, a professor at Carnegie Mellon University,

said that another effective tactic TikTok has employed is to

encourage its users to form groups publicly via hashtags.

By encouraging users to form public groups, TikTok can more

effectively learn about its users' behavior, interest, alignment

and ideology, he said.

If TikTok ends up getting banned in the U.S., Lightman

said that while the U.S. tech giants certainly have the

capability to replicate TikTok with their own products,

replicating the user culture enabled by TikTok might be the

bigger task.

CHINESE ADVANTAGE

TikTok's recommendation algorithm was also in large part

taken from its Chinese sister app Douyin which was released in

2016. Although ByteDance often stresses that TikTok and Douyin

are separate apps, one source with direct knowledge of the

matter said the two algorithms remain similar to this day.

In turn, Douyin's AI was supercharged by the company's

ability to leverage low labour costs in China that saw it hire

many content annotators to painstakingly tag all the content and

users on the platform.

"Around 2018 and 2019, Douyin worked on having tags on every

user. So they would tag every video clip manually. Then they

would tag their users based on the video that they have

watched," said Yikai Li, a manager at ad agency Nativex and a

former director at ByteDance. "Then they also applied this

tactic on TikTok."

While hiring annotators to tag data is now a common and an

important practice for AI companies, ByteDance was early in

adopting this strategy.

"It's a lot of work sorting out these tags. It's very

laborious," he said, "So Chinese companies have an advantage

here. You can afford a lot more people. The cost is cheaper than

it is for North American companies."