This article originally appeared on ABACUS We’re just a few days away from the 30th anniversary of the June 4th Tiananmen Square crackdown, which means China’s censors are hard at work as internet users find there are fewer places for them to comment online. One very conspicuous target of censors this year is “bullet chat.” Originated in Japan and popularized in China by anime video site Bilibili, fly-by comments overlaid on videos is an iconic feature for many video streamers in China. Bilibili, China’s biggest anime site, covers the screen in user comments On May 29, five video sites -- anime sites Bilibili and AcFun and live-streaming platforms Douyu, Huya and YY Live -- all said that they would suspend their bullet comment function until June 6. They all cited the same reason: “System upgrade and maintenance.” Previously-posted comments are not affected, but users will not be able to post any new bullet chats during this period. But this is China we’re talking about, so of course many people aren’t buying the “system upgrade” excuse. “What a coincidence,” one Weibo user said sarcastically. “Maybe everyone is troubled by a super bug.” There’s nothing new about Chinese censors tightening controls online around June 4th. It happens every year. It’s become normal for censors to scrub texts and pictures associated with the Tiananmen crackdown from social media platforms such as Weibo and WeChat. They also more heavily block Great Firewall circumvention tools like VPNs. To get around the censors, users have increasingly relied on obscure references like these ones collected by Weiboscope , a project by a professor at the University of Hong Kong. But many netizens still can’t escape censorship as the government deploys more human censors and more powerful tools. Through the use of machine learning and image recognition, these tools have achieved a new level of accuracy, according to Reuters . But bullet chats may still be difficult territory for censors. The Cyberspace Administration of China said in a 2017 article that bullet chats are hard to censor because they are published in real time and usually come in big numbers. The various shapes and colors as seen on Bilibili can’t help, either. In February this year , authorities urged tech companies to double down on censoring bullet chats, asking them to “manage them in real time” and only let through comments that they have checked. That would be very challenging for video sites , and it’s not clear how effective their efforts have been. So it looks like the most effective method of cracking down right now is just suspending the function altogether. Chinese censors aren’t known for their light touch, of course. Sometimes an entire online community might get caught up in the dragnet. On May 30, interest-based social site Douban said it’s suspending for a month one popular group where people post topics about celebrity gossip and social issues. For more insights into China tech, sign up for our tech newsletters , subscribe to our Inside China Tech podcast , and download the comprehensive 2019 China Internet Report . Also roam China Tech City , an award-winning interactive digital map at our sister site Abacus .