It’s less than a week after the 30th anniversary of the June 4 Tiananmen Square crackdown, and China’s censors are busy at work again.

On June 9, more than one million people took to the streets in Hong Kong, according to event organizers, to rally against an extradition bill that people fear will allow the Chinese government to snatch anybody they want from Hong Kong. It was the largest protest in the city in over a decade, with approximately one in seven people in Hong Kong joining the march.

But in mainland China, where the government has an increasingly tight grip on online information, the event was largely unnoticed.

A peaceful protest lasted for nearly 10 hours, but it ended with a violent clash between police and protesters. (Picture: Thomas Leung/Abacus)

Mainland news outlets had no major coverage of the event, except for some mentions in state media.

On Monday morning, Global Times published an editorial in Chinese titled “Hong Kong’s overall situation won’t be shaken by opposition groups colluding with the West.” The piece mentioned the rally in Hong Kong, but it said organizers “used the old trick” of hyping the number of protesters who attended and that the rally was fueled by interference from Western countries.

Many in China still use VPNs to get past the Great Firewall for information, though, and some people who saw the news tried to start a discussion. Many of the comments were promptly censored.

“I suggest that everyone climb out of the wall and see what’s happening in Hong Kong,” said one Weibo user, referring to China’s Great Firewall that blocks a number of foreign websites. The user’s Weibo account can no longer be found.

“Such a big event happening in Hong Kong today and we can’t see any news inside the wall,” another Weibo user wrote in a now-censored post that included screenshots of a CNN story.

Weibo users are expressing their support for Hong Kong people, some using the fuel pump emoji to say “add oil.” (Picture: Weibo)

Apart from scrubbing posts that mention the protest, a search of relevant keywords on Weibo -- including “Hong Kong,” “HK” and “extradition bill” -- only generates results from official sources or entertainment news. People are also saying that their WeChat accounts were suspended after sharing pictures of the protest in group chats.

“It’s gotten so big in Hong Kong, but it’s absolute silence inside the wall,” a Weibo user said. “Most people don’t know, and those who do know dare not speak of it.”

China has a long history of censoring social media posts, but censorship is getting increasingly powerful through the use of machine learning and image recognition. It’s increasingly encroaching on more parts of the internet, as well.

Leading up to June 4 this year, one of China’s favorite forms of real-time chat went mysteriously silent. “Bullet chat,” where real-time comments fly across the screen over streaming video, was completely suspended ahead of the Tiananmen Square anniversary, with all platforms citing “system upgrade and maintenance.”

News sites The Guardian and The Washington Post have also just been added to the firewall blacklist. They were two of the few major English-language news sites that hadn’t been blocked.

“The presence of the wall means that what triggered heated discussion among everyone in Hong Kong doesn’t cause a splash on the mainland internet,” a Weibo user said in a post that’s no longer available. “It’s really two worlds in and outside China.”