Today—the day known to much of the rest of the world as the 25th anniversary of the Tiananmen Square protests—is known, in China, as "Internet maintenance day." In anticipation of the anniversary, the PRC's censors have strategically shut down Internet services (Google's among them). It's a silent holiday, for the most part: As the Wall Street Journal's Jason Ng notes, the People’s Daily, the country's Communist Party newspaper, led today's front page with a story about Xi Jinping’s attendance of an engineering conference.
As schemes for enforcing silence, these approaches—shutdowns, distractions—are sweeping. But when it comes to Sina Weibo, the PRC's analog to Twitter, China's censorship-savvy government seems to have adopted a more surgical strategy. Ng, writing for the Journal's China Realtime blog, has identified 64 terms that are currently censored on the network: "Tiananmen" and "June 4" and "tank man" in varying permutations.
"As recently as May 11," Ng writes, "the Chinese words for 'tank' and '64' (short for June 4) were unblocked, but based on tests today, these and many other June 4-related keywords have now been restricted from searching." So, basically, if you try to look up anything on Weibo that uses a censored keyword—like the numbers 六 (6) or 四 (4) or the characters 坦克 (tank)—your search will come up blank.