Kelley Cotter, Penn State

Chinese tech giant ByteDance has signed an agreement to sell a majority stake in its video platform TikTok to a group of U.S. investors. President Donald Trump announced a preliminary agreement for the sale on Sept. 19, 2025, following his negotiation with Chinese leader Xi Jinping.

TikTok CEO Shou Zi Chew told employees in a memo obtained by news organizations that the company is working to close the deal by Jan. 22, 2026. Chinese and U.S. authorities will also need to approve the deal.

The deal creates a new U.S.-only version of the app, bringing it into compliance with a law signed by President Joe Biden on April 23, 2024, and upheld by the Supreme Court on Jan. 17, 2025. Specifics of the deal remain to be hammered out, but some details are emerging. These include what will happen to the video-sharing app’s core algorithm – and what that means for TikTok’s millions of U.S. users.

The Chinese government has indicated it will not permit ByteDance to sell the algorithm, because it is classified as a controlled technology export, per Chinese law. Meanwhile, U.S. tech industry executives and some lawmakers say compliance with the law requires the algorithm to be under American control. The deal as proposed includes licensing the algorithm so that it remains Chinese intellectual property while the U.S. version of the app continues to use the technology.

TikTok’s “For You” page algorithm is widely considered the most important part of the app. As one analyst put it: “Buying TikTok without the algorithm would be like buying a Ferrari without the engine.”

The algorithm’s value lies in its uncanny capacity to anticipate users’ content preferences. Many users claim it knows them better than they know themselves – a sentiment that has evolved into a curious mix of spiritual belief and conspiracy theorizing, as my colleagues and I have documented. Other scholars have similarly noted that users feel more intimately seen and known by TikTok’s algorithm than those powering other popular platforms.

I have studied social media algorithms for nearly a decade, exploring how our relationships with them have evolved as they become increasingly entwined with daily life. As both a social media scholar and TikTok devotee, I want to shed some light on how the algorithm works and how the app is likely to change in the wake of its sale.

How the TikTok algorithm works

In some ways, the TikTok algorithm does not differ significantly from other social media algorithms. At their core, algorithms are merely a series of steps used to accomplish a specific goal. They perform mathematical computations to optimize output in service of that goal.

There are two layers to the TikTok algorithm. First, there is the abstract layer that defines the outcome developers wish to accomplish. An internal document shared with The New York Times specified that TikTok’s algorithm optimizes for four goals: “user value,” “long-term user value,” “creator value” and “platform value.”

But how do you turn these goals into math? What does an abstract concept like “user value” even mean? It’s not practical to ask users whether they value their experience every time they visit the site. Instead, TikTok relies on proxy signals that translate abstract outcomes into quantifiable measures – specifically, likes, comments, shares, follows, time spent on a given video and other user-behavior data. These signals then become part of an equation to predict two key concrete outcomes: “retention,” or the likelihood that a user will return to the site, and “time spent” on the app.

The TikTok For You page algorithm relies on machine learning for predicting retention and time spent. Machine learning is a computational process in which an algorithm learns patterns in a dataset, with little or no human guidance, to produce the best equation to predict an outcome. Through learning patterns, the algorithm determines how much individual data signals matter for coming up with a precise prediction.

A Wall Street Journal investigation found that the amount of time users spend watching each video plays a large role in how the algorithm chooses videos it suggests to users. Using the equation it has generated to predict retention and time spent, the algorithm assigns a score to each video and ranks possible videos that could be shown to the user by this score. The higher the score for an individual user, the more likely the video will appear in their feed.

Of course, content characteristics and other users additionally inform recommendations, and there are other subprocesses folded into the equation. This step is where algorithmic moderation usually comes in. If a video looks like engagement bait or has excessive gore, for example, the content’s score will be penalized.

What’s likely to change for US users

The sale has not been finalized, but the algorithm’s fate is coming into focus. According to reports, the United States-only version of the algorithm will be retrained on only U.S. users’ data. Users won’t need to download a new version of the app for the changed algorithm to work.

Even though the algorithm itself is the same as before, it’s fairly certain that TikTok will change. I see two key reasons for change.

First, the proposed app’s U.S.-only user population will alter the makeup of the underlying dataset informing algorithmic recommendations on an ongoing basis. As the kinds of content come to reflect American cultural preferences, values and behaviors, the algorithm may be slightly different as it “learns” new patterns.

Though users are more likely to stick with the app because they don’t need to download a new version, not all users will choose to, especially if it is seen as under the control of Trump’s allies. Under the current deal, Oracle Corp. and the U.S. government would oversee the algorithm’s retraining. This arrangement suggests that the U.S. government may have significant influence over how the app works.

The deal would give an 80% share to U.S. investors, including 50% to new investors Oracle, Silver Lake and Andreessen Horowitz. These investors have connections to Trump, and an apparent provision of the deal allows the U.S. government to select one board member.

These influences raise the possibility of a boycott from left-leaning users and creators similar to earlier boycotts of Target for rolling back DEI measures and Disney after the since-reversed suspension of Jimmy Kimmel. This may result in a user population – and data – reflective of a narrower realm of interests and ideologies.

Second, it’s possible that the majority shareowners of the new app will decide to adjust the algorithm, particularly when it comes to content moderation. The new owners may wish to modify TikTok’s Community Guidelines according to their view of acceptable and unacceptable speech.

For example, TikTok’s current Community Guidelines prohibit misinformation and work with independent fact-checkers to assess the accuracy of content. While Meta used to follow a similar approach for Instagram and Facebook, in January 2025 Meta announced that it would end its relationships with independent fact-checkers and loosen content restrictions. YouTube has similarly relaxed its content moderation this year.

With reports that the U.S. government would oversee retraining the algorithm, there’s a possibility that not only the new investors but also the government itself could influence how content is prioritized and moderated.

The bottom line is algorithms are highly sensitive to context. They reflect the interests, values and worldviews of the people who build them, the preferences and behaviors of people whose data informs their models and the legal and economic contexts they operate within.

This means that while it’s difficult to predict exactly what a U.S.-only TikTok will be like, it’s safe to assume it will not be a perfect mirror image of the current app.

This story was updated on Dec. 19, 2025, to include new details about TikTok’s sale.

Kelley Cotter, Assistant Professor of Information Sciences and Technology, Penn State

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Matthew L. Druckenmiller, University of Colorado Boulder; Rick Thoman, University of Alaska Fairbanks, and Twila A. Moon, University of Colorado Boulder

The Arctic is transforming faster and with more far-reaching consequences than scientists expected just 20 years ago, when the first Arctic Report Card assessed the state of Earth’s far northern environment.

The snow season is dramatically shorter today, sea ice is thinning and melting earlier, and wildfire seasons are getting worse. Increasing ocean heat is reshaping ecosystems as non-Arctic marine species move northward. Thawing permafrost is releasing iron and other minerals into rivers, which degrades drinking water. And extreme storms fueled by warming seas are putting communities at risk.

The past water year, October 2024 through September 2025, brought the highest Arctic air temperatures since records began 125 years ago, including the warmest autumn ever measured and a winter and a summer that were among the warmest on record. Overall, the Arctic is warming more than twice as fast as the Earth as a whole.

For the 20th Arctic Report Card, we worked with the National Oceanic and Atmospheric Administration, an international team of scientists and Indigenous partners from across the Arctic to track environmental changes in the North – from air and ocean temperatures to sea ice, snow, glaciers and ecosystems – and the impacts on communities.

Together, these vital signs reveal a striking and interconnected transformation underway that’s amplifying risks for people who live there.

A wetter Arctic with more extreme precipitation

Arctic warming is intensifying the region’s water cycle.

A warmer atmosphere increases evaporation, precipitation and meltwater from snow and ice, adding and moving more water through the climate system. That leads to more extreme rainstorms and snowstorms, changing river flows and altering ecosystems.

The Arctic region saw record-high precipitation for the entire 2025 water year and for spring, with the other seasons each among the top-five wettest since at least 1950. Extreme weather – particularly atmospheric rivers, which are long narrow “rivers in the sky” that transport large amounts of water vapor – played an outsized role.

These wetter conditions are reshaping snow cover across the region.

Snow and ice losses accelerate warming, hazards

Snow blankets the Arctic throughout much of the year, but that snow cover isn’t lasting as long. In 2025, snowpack was above average in the cold winter months, yet rapid spring melting left the area covered by snow far smaller than normal by June, continuing a six-decade decline. June snow cover in recent years has been half of what it was in the 1960s.

Losing late spring snow cover means losing a bright, reflective surface that helps keep the Arctic cool, allowing the land instead to be directly warmed by the sun, which raises the temperature.

Sea ice tells a similar story. The year’s maximum sea ice coverage, reached in March, was the lowest in the 47-year satellite record. The minimum sea ice coverage, in September, was the 10th lowest.

Since the 1980s, the summer sea ice extent has shrunk by about 50%, while the area covered by the oldest, thickest sea ice – ice that has existed for longer than four years – has declined by more than 95%.

The thinner sea ice cover is more influenced by winds and currents, and less resilient against warming waters. This means greater variability in sea ice conditions, causing new risks for people living and working in the Arctic.

The Greenland Ice Sheet continued to lose mass in 2025, as it has every year since the late 1990s. As the ice sheet melts and calves more icebergs into the surrounding seas, it adds to global sea-level rise.

Mountain glaciers are also losing ice at an extraordinary rate – the annual rate of glacier ice loss across the Arctic has tripled since the 1990s.

This poses immediate local hazards. Glacial lake outburst floods – when water that is dammed up by a glacier is suddenly released – are becoming more frequent. In Juneau, Alaska, recent outburst floods from Mendenhall Glacier have inundated homes and displaced residents with record-setting levels of floodwater.

Glacier retreat can also contribute to catastrophic landslide impacts. Following the retreat of South Sawyer Glacier, a landslide in southeast Alaska’s Tracy Arm in August 2025 generated a tsunami that swept across the narrow fjord and ran nearly 1,600 feet (nearly 490 meters) up the other side. Fortunately, the fjord was empty of the cruise ships that regularly visit.

Record-warm oceans drive storms, ecosystem shifts

Arctic Ocean surface waters are steadily warming, with August 2025 temperatures among the highest ever measured. In some Atlantic-sector regions, sea surface temperatures were as much as 13 degrees Fahrenheit (7.2 Celsius) above the 1991-2020 average. Some parts of the Chukchi and Beaufort seas were cooler than normal.

Warm water in the Bering Sea set the stage for one of the year’s most devastating events: Ex-Typhoon Halong, which fed on unusually warm ocean temperatures before slamming into western Alaska with hurricane-force winds and catastrophic flooding. Some villages, including Kipnuk and Kwigillingok, were heavily damaged.

As seas warm, powerful Pacific cyclones, which draw energy from warm water, are reaching higher latitudes and maintaining strength longer. Alaska’s Arctic has seen four ex-typhoons since 1970, and three of them arrived in the past four years.

The Arctic is also seeing warmer, saltier Atlantic Ocean water intrude northward into the Arctic Ocean. This process, known as Atlantification, weakens the natural layering of water that once shielded sea ice from deeper ocean heat. It is already increasing sea ice loss and reshaping habitat for marine life, such as by changing the timing of phytoplankton production, which provides the base of the ocean food web, and increasing the likelihood of harmful algal blooms.

From ocean ‘borealization’ to tundra greening

Warming seas and declining sea ice are enabling southern, or boreal, marine species to move northward. In the northern Bering and Chukchi seas, Arctic species have declined sharply – by two-thirds and one-half, respectively – while the populations of boreal species expand.

On land, a similar “borealization” is underway. Satellite data shows that tundra vegetation productivity – known as tundra greenness – hit its third-highest level in the 26-year record in 2025, part of a trend driven by longer growing seasons and warmer temperatures. Yet greening is not universal – browning events caused by wildfires and extreme weather are also increasing.

Summer 2025 marked the fourth consecutive year with above-median wildfire area across northern North America. Nearly 1,600 square miles (over 4,000 square kilometers) burned in Alaska and over 5,000 square miles (over 13,600 square kilometers) burned in Canada’s Northwest Territories.

Permafrost thaw is turning rivers orange

As permafrost – the frozen ground that underlies much of the Arctic – continues its long-term warming and thaw, one emerging consequence is the spread of rusting rivers.

As thawing soils release iron and other minerals, more than 200 watersheds across Arctic Alaska now show orange discoloration. These waters exhibit higher acidity and elevated levels of toxic metals, which can contaminate fish habitat and drinking water and impact subsistence livelihoods.

In Kobuk Valley National Park in Alaska, a tributary to the Akillik River lost all its juvenile Dolly Varden and slimy sculpin fish after an abrupt increase in stream acidity when the stream turned orange.

Arctic communities lead new monitoring efforts

The rapid pace of change underscores the need for strong Arctic monitoring systems. Yet many government-funded observing networks face funding shortfalls and other vulnerabilities.

At the same time, Indigenous communities are leading new efforts.

The Arctic Report Card details how the people of St. Paul Island, in the Bering Sea, have spent over 20 years building and operating their own observation system, drawing on research partnerships with outside scientists while retaining control over monitoring, data and sharing of results. The Indigenous Sentinels Network tracks environmental conditions ranging from mercury in traditional foods to coastal erosion and fish habitat and is building local climate resilience in one of the most rapidly changing environments on the planet.

The Arctic is facing threats from more than the changing climate; it’s also a region where concerns of ecosystem health and pollutants come sharply into view. In this sense, the Arctic provides a vantage point for addressing the triple planetary crisis of climate change, biodiversity loss and pollution.

The next 20 years will continue to reshape the Arctic, with changes felt by communities and economies across the planet.

Matthew L. Druckenmiller, Senior Scientist, National Snow and Ice Data Center (NSIDC), Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado Boulder; Rick Thoman, Alaska Climate Specialist, University of Alaska Fairbanks, and Twila A. Moon, Deputy Lead Scientist, National Snow and Ice Data Center (NSIDC), Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado Boulder

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Greg Barton, Deakin University

With 15 civilians and one gunman dead so far, and another 40 people injured, Australia is reeling from its worst act of terrorism on home soil. Two gunmen opened fire on a Jewish community gathering to celebrate the first night of Hanukkah at Archer Park on Sydney’s famous Bondi Beach.

Police have confirmed the two alleged attackers were father and son, aged 50 and 24. The father, Sajid Akram, who was licensed to own six firearms, was shot dead by police. The son, Naveed Akram, remains under police guard in hospital.

Given it was clearly an antisemitic attack, authorities soon after declared it an act of terrorism – that is, an act of politically motivated violence. This designation also gives authorities extra resources in their response and in bringing those responsible to justice.

As Australians try to process their shock and grief, there has been some anger in the community that not enough has been done to protect Jewish Australians from the rising antisemitism evident since the Hamas attack on Israel in October 2023 and the ensuing Gaza war.

What we know about the alleged attackers

ASIO (The Australian Security Intelligence Organisation) Director-General Mike Burgess has said one of the alleged gunmen was “known” to ASIO, though he did not specify which one. Being “known” to authorities can simply mean someone has been associated with networks and communications that have caused concern to authorities. The ABC has reported that Naveed Akram came to the attention of authorities after the arrest of Islamic State Sydney cell leader Isaac El Matari in July 2019.

However, there are hundreds of people who come to authorities’ attention for their contact, online or off, with extremist networks and individuals. With limited resources (and authorities’ resources will always be limited, no matter how much funding they have), they have to run a triage system to assess the threat an individual or a group may pose, and manage the risk as best they can.

They will carefully assess what is being said and the language used, for example, as well as looking at whether a person has a history of violence. As angry and upset as people understandably are in the wake of such a horrific incident, it needs to be recognised that authorities can’t simply arrest everyone who expresses extremist ideas or has passing links with extremist elements.

We still need to know more about this terror attack and the alleged attackers, but to date there has been no evidence of a network in operation. Given the alleged gunmen were father and son, this technically fits the profile of a “lone actor” attack, as we saw in the Lindt Cafe siege in 2014, and Christchurch in 2019.

It is very difficult for authorities to predict and therefore prevent lone actor attacks – by their nature, there’s often no sign beforehand of the potential for violence. And public sites like the reserve at Bondi Beach require extensive resources to police, meaning not all can be adequately secured.

As Burgess pointed out in his annual threat assessment, “our greatest threat remains a lone actor using an easily obtained weapon”. Sadly, that has been shown to be true.

Changing nature of terrorist threat in Australia

There has been much attention in recent years on the rise of far-right extremism and terrorism.

One of the best guides to this is Burgess’ annual threat assessment. In it he explained that a decade ago, just one in ten cases ASIO was following up involved right-wing extremists, with radical Islamist groups occupying most of their attention. However, in recent years the ratio has shifted closer to one in two investigations involving right-wing extremism. In other words, a lot of ASIO’s attention and resources are now necessarily tied up with combating right-wing extremism, especially following the Christchurch terror attack in which 51 people were shot dead by an Australian far-right terrorist during Friday prayers in two New Zealand mosques.

More broadly, Islamic terrorism continues to remain a global threat. IS and Al-Qaeda remain active in the Middle East and increasingly in Africa, as well as central Asia and Afghanistan. Generally, authorities are doing a good job of keeping on top of any threats these networks might pose in Australia.

There is no doubt the general atmosphere between pro-Palestinian and Jewish groups has become far more febrile in the wake of the Hamas attack and the Gaza war. There is a lot of anger and frustration as scenes of violence and suffering are broadcast daily, and we have seen a rise both in antisemitism and Islamophobia since the war began, simply because of the way it plays out in people’s imaginations.

But even in the protests we have seen over many months, the number of people who might use this sentiment to spur violence is small.

Again, there is no evidence the Bondi shooting was part of a wider network, and it is very difficult to stop a lone actor attack on a public site.

In a glimmer of hope, the man whose much-lauded act of heroism in wrestling one of the alleged gunman’s weapons from him has been named as 43-year-old Muslim fruit shop owner Ahmed Al-Ahmed. It is hoped this man’s bravery, which showed us the best of humanity in the midst of the worst, will stop any simplistic analysis of blaming the Muslim community for such violence. We have seen this in the United States, and Australia must do much better.

Has the government done enough?

It is very difficult to keep outdoor public events entirely safe: buildings are relatively easy to secure, but a park at a beach far less so.

The government clearly needs to do more to stop terrorism, and public events are an obvious focus for more resources. No one should be satisfied with where we are right now. It is simply horrifying. But it’s going to take a lot of work to figure out where we can best use resources.

We can’t close every loophole or thwart every risk. We can’t stop people turning to violence, and we can’t police every hateful thought. It has been said this was an attack on all of us, and that’s very true. As the message of Hanukkah inspires us, now is the time when we need to pull together as Australians from all faiths and communities, and work together to ensure that light triumphs over darkness.

Greg Barton, Chair in Global Islamic Politics, Alfred Deakin Institute for Citizenship and Globalisation, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.