Microsoft’s Bing was down in China, according to users who took to social media beginning Wednesday afternoon to complain and express concerns.

The Seattle-based behemoth confirmed that its search engine was inaccessible in China for a time, and was “engaged to determine next steps,” a company spokesperson said in a statement to TechCrunch Thursday morning.

Later, the company said: “We can confirm that Bing was inaccessible in China, but service is now restored.”

Citing sources, the Financial Times reported (paywalled) on Thursday that China Unicom, a major state-owned telecommunication company, said that the government had ordered a block on Bing.

Public reaction

The situation appears to be a DNS (domain name system) corruption, one method for China to block websites through its intricate censoring system called the Great Firewall. When a user enters a domain name associated with a banned IP address, the Firewall will corrupt the connection to stop the page from loading.

Several users told TechCrunch they are still able to access Bing by directly visiting its IP address as of Thursday morning.

UPDATE: it's confirmed to be DNS corruption, the common method of banning websites in China pic.twitter.com/GIlYsCVa1L — Patrick Wu (@patrick330602) January 23, 2019

Other users writing on social media believe the block was a result of Bing’s server crash after a viral article (link in Chinese) attacking Baidu’s search quality directed traffic to its lesser-known American rival. Many referred to a Chinese report that says high traffic from Baidu crashed Bing. The article, published by Jiemian, a news site under the state-owned Shanghai United Media Group, now returns a 404 “not found”error.

Microsoft has long tried to play by China’s rules by filtering out sensitive results from its search engine. It also modified Windows 10 for China back in 2017 through a collaboration with state-owned China Electronics Technology Group to eliminate Beijing’s fears of possible backdoors in the American software.

Former Microsoft executive Steven Sinofsky lamented Bing’s blockage in China, writing on Twitter that Microsoft had “worked so hard to be successful there.”

Microsoft search engine Bing is blocked in China https://t.co/i4jv3JRPFM // No idea what is going on–based on this I am sad. Since 2003 or so had we worked so hard to be successful there. Even went and lived there, built relationships. China's Pres. visited US and more. 💔 — Steven Sinofsky (@stevesi) January 24, 2019

Tight seal

Bing remains one of the few non-Chinese internet firms that still have their core products up and running in a country where Google and Facebook have long been unavailable. Another rare case is LinkedIn, which runs a filtered version of its social network for professionals and caught flack for bending to local censorship.

Bing also censors its search service for Chinese users, so it would be odd if its inaccessibility proves to be a case of government clampdown. That said, China continues to further tighten control over the cyberspace. Case in point, LinkedIn recently started to run strict identity checks on its China-based users.

Baidu remains the biggest search engine in China, with smaller rival Sogou coming in second. Bing, which some users find is a more pleasant alternative to local options that are usually flooded with ads, is active on 320,000 unique devices monthly, according to third-party research firm, iResearch. That’s dwarfed by Baidu’s 466 million and Sogou’s 43 million devices.

Google told the U.S. Congress in December it had no immediate plans to relaunch its search engine in China but felt “reaching out and giving users more information has a very positive impact.” The Mountain View, California-based firm shut down its search engine in mainland China back in 2010 under pressure over censorship but also cited cyberattacks as a factor in its decision to leave.