[TAIPEI] Just after the 2016 presidential election in the United States, Joanne Li realized the app that connected her to fellow Chinese immigrants had disconnected her from reality.

Everything she saw on the Chinese app, WeChat, indicated Donald Trump was an admired leader and impressive businessman. She believed it was the unquestioned consensus on the newly elected US president. "But then I started talking to some foreigners about him, non-Chinese," she said. "I was totally confused." She began to read more widely, and Ms Li, who lived in Toronto at the time, increasingly found WeChat filled with gossip, conspiracy theories and outright lies. One article claimed Prime Minister Justin Trudeau of Canada planned to legalise hard drugs. Another rumour purported that Canada had begun selling marijuana in grocery stores. A post from a news account in Shanghai warned Chinese people to take care lest they accidentally bring the drug back from Canada and get arrested.

She also questioned what was being said about China. When a top Huawei executive was arrested in Canada in 2018, articles from foreign news media were quickly censored on WeChat. Her Chinese friends both inside and outside China began to say that Canada had no justice, which contradicted her own experience. "All of a sudden I discovered talking to others about the issue didn't make sense," Li said. "It felt like if I only watched Chinese media, all of my thoughts would be different." Li had little choice but to take the bad with the good. Built to be everything for everyone, WeChat is indispensable.

For most Chinese people in China, WeChat is a sort of all-in-one app: a way to swap stories, talk to old classmates, pay bills, coordinate with co-workers, post envy-inducing vacation photos, buy stuff and get news. For the millions of members of China's diaspora, it is the bridge that links them to the trappings of home, from family chatter to food photos.

Woven through it all is the ever more muscular surveillance and propaganda of the Chinese Communist Party. As WeChat has become ubiquitous, it has become a powerful tool of social control, a way for Chinese authorities to guide and police what people say, who they talk to and what they read.

It has even extended Beijing's reach beyond its borders. When secret police issue threats abroad, they often do so on WeChat. When military researchers working undercover in the US needed to talk to China's embassies, they used WeChat, according to court documents. The party coordinates via WeChat with members studying overseas.

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As a cornerstone of China's surveillance state, WeChat is now considered a national security threat in the US. The Trump administration has proposed banning WeChat outright, along with the Chinese short video app TikTok. Overnight, two of China's biggest internet innovations became a new front in the sprawling tech standoff between China and the US.

While the two apps are lumped in the same category by the Trump administration, they represent two distinct approaches to the Great Firewall that blocks Chinese access to foreign websites.

The hipper, better-known TikTok was designed for the wild world outside of China's cloistering censorship; it exists only beyond China's borders. By hiving off an independent app to win over global users, TikTok's owner, ByteDance, created the best bet any Chinese startup has had to compete with the internet giants in the West. The separation of TikTok from its cousin apps in China, along with deep popularity, has fed corporate campaigns in the US to save it, even as Beijing potentially upended any deals by labelling its core technology a national security priority.

Though WeChat has different rules for users inside and outside of China, it remains a single, unified social network spanning China's Great Firewall. In that sense, it has helped bring Chinese censorship to the world. A ban would cut dead millions of conversations between family and friends, a reason one group has filed a lawsuit to block the Trump administration's efforts. It would also be an easy victory for US policymakers seeking to push back against China's techno-authoritarian overreach.

Ms Li felt the whipcrack of China's internet controls firsthand when she returned to China in 2018 to take a real estate job. After her experience overseas, she sought to balance her news diet with groups that shared articles on world events. As the coronavirus spread in early 2020 and China's relations with countries around the world strained, she posted an article on WeChat from the US government-run Radio Free Asia about the deterioration of Chinese-Canadian diplomacy, a piece that would have been censored.

The next day, four police officers showed up at her family's apartment. They carried guns and riot shields.

"My mother was terrified," she said. "She turned white when she saw them." The police officers took Ms Li, along with her phone and computer, to the local police station. She said they manacled her legs to a restraining device known as a tiger chair for questioning. They asked repeatedly about the article and her WeChat contacts overseas before locking her in a barred cell for the night.

Twice she was released, only to be dragged back to the station for fresh interrogation sessions. Ms Li said an officer even insisted China had freedom of speech protections as he questioned her over what she had said online. "I didn't say anything," she said. "I just thought, what is your freedom of speech? Is it the freedom to drag me down to the police station and keep me night after sleepless night interrogating me?" Finally, the police forced her to write out a confession and vow of support for China, then let her go.

'THE WALLS ARE GETTING HIGHER'

WeChat started out as a simple copycat. Its parent, Chinese internet giant Tencent, had built an enormous user base on a chat app designed for personal computers. But a new generation of mobile chat apps threatened to upset its hold over the way young Chinese talked to one another.

Visionary Tencent engineer Allen Zhang fired off a message to the company founder, Pony Ma, concerned that they weren't keeping up. The missive led to a new mandate, and Mr Zhang fashioned a digital Swiss Army knife that became a necessity for daily life in China. WeChat piggybacked on the popularity of the other online platforms run by Tencent, combining payments, e-commerce and social media into a single service.

It became a hit, eventually eclipsing the apps that inspired WeChat. And Tencent, which made billions in profits from the online games piped into its disparate platforms, now had a way to make money off nearly every aspect of a person's digital identity - by serving ads, selling stuff, processing payments and facilitating services like food delivery.

The tech world inside and outside of China marvelled. Tencent rival Alibaba scrambled to come up with its own product to compete. Silicon Valley studied the ways it mixed services and followed its cues.

Built for China's closed world of internet services, WeChat's only failure came outside the Great Firewall. Tencent made a big marketing push overseas, even hiring soccer player Lionel Messi as a spokesperson in some markets. For non-China users, it created a separate set of rules. International accounts would not face direct censorship and data would be stored on servers overseas.

But WeChat didn't have the same appeal without the many services available only in China. It looked more prosaic outside the country, like any other chat app. The main overseas users, in the end, would be the Chinese diaspora.

Tencent did not respond to a request for comment.

Over time, the distinctions between the Chinese and international app have mattered less. Chinese people who create accounts within China, but then leave, carry with them a censored and monitored account. If international users chat with users inside China, their posts can be censored.

For news and gossip, most comes from WeChat users inside China and spreads out to the world. Whereas most social networks have myriad filter bubbles that reinforce different biases, WeChat is dominated by one super-filter bubble, and it hews closely to the official propaganda narratives.

"The filter bubbles on WeChat have nothing to do with algorithms - they come from China's closed internet ecosystem and censorship. That makes them worse than other social media," said Fang Kecheng, a professor in the School of Journalism and Communications at the Chinese University of Hong Kong.

Mr Fang first noticed the limitations of WeChat in 2018 as a graduate student at the University of Pennsylvania, teaching an online course in media literacy to younger Chinese.

Soft-spoken and steeped in the media echo chambers of the US and China, Mr Fang expected to reach mostly curious Chinese inside China. An unexpected group dialled into the classes: Chinese immigrants and expatriates living in the US, Canada and elsewhere.

"It seemed obvious. Because they were all outside China, it should be easy for them to gain an understanding of foreign media. In their day-to-day life they would see it and read it," Mr Fang said. "I realised it wasn't the case. They were outside of China, but their media environment was still entirely inside China, their channel for information was all from public accounts on WeChat." Mr Fang's six-week online courses were inspired by a WeChat account he ran called News Lab that sought to teach readers about journalism. With his courses, he assigned articles from media like Reuters along with worksheets that taught students to analyse the pieces - pushing them to draw distinctions between pundit commentary and primary sourcing.

In a class in 2019, he warned broadly about barriers to information flow.

"Now, the walls are getting higher and higher. The ability to see the outside has become ever harder," he said. "Not just in China, but in much of the world."

'WHAT IT'S LIKE TO LOSE CONTACT'

When Ferkat Jawdat's mother disappeared into China's sprawling system of reeducation camps to indoctrinate Uighurs, his WeChat became a kind of memorial.

The app might have been used as evidence against her. But he, like many Uighurs, found himself opening WeChat again and again. It contained years of photos and conversations with his mother. It also held a remote hope he clung to, that one day she would again reach out.

When against all odds she did, the secret police followed.

Mr Jawdat's mother, sick and worn, was released from the camps in the summer of 2019. Chinese police gave her a phone and signed her into WeChat. At the sound of his mother's voice Mr Jawdat fought back a flood of emotions. He hadn't been sure if she was even alive. Despite the relief, he noticed something was off. She offered stilted words of praise for the Chinese Communist Party.

Then the police reached out to him. They approached him with an anonymous friend request over WeChat. When he accepted, a man introduced himself as a high-ranking officer in China's security forces in the Xinjiang region, the epicentre of reeducation camps. The man had a proposal. If Mr Jawdat, a US citizen and Uighur activist, would quiet his attempts to raise awareness about the camps, then his mother might be given a passport and allowed to join her family in the US.

"It was a kind of threat," he said. "I stayed quiet for two or three weeks, just to see what he did." It all came to nothing. After turning down a media interview and skipping a speaking event, Mr Jawdat grew impatient and confronted the man. "He started threatening me, saying, 'You're only one person going against the superpower. Compared to China, you are nothing.'" The experience gave Mr Jawdat little tolerance for the app that made the threats possible, even if it had been his only line to his mother. He said he knew two other Uighur Americans who had similar experiences. Accounts from others point to similar occurrences around the world.

"I don't know if it's karma or justice served, for the Chinese people to also feel the pain of what it's like to lose contact with your family members," Mr Jawdat said of the proposed ban by the Trump administration. "There are many Chinese officials who have their kids in the US. WeChat must be one of the tools they use to keep in contact. If they feel this pain, maybe they can relate better to the Uighurs."

NYTIMES