Reporting from Beijing — For a couple of precious hours Monday, the Chinese government's Web censoring system, popularly known as the Great Firewall, was lifted. Suddenly, Internet users had access to websites that had been banned for months, including YouTube, Facebook and Twitter.
Cautious excitement spread on some social-networking platforms that authorities were expanding Internet freedoms. But by the time most Chinese woke up the restrictions were back. Error messages once again flashed across computer screens for sites blocked by the nation's censorship filter.
"It seemed just like a dream," said Michael Anti, a social critic and one of hundreds who tweeted about the development on Twitter.
In many respects, it was.
Savvy computer users have found ways to scale the Great Firewall. But the vast majority of China's netizens face limits on their Internet wanderings, and that's likely to continue.
"The government isn't showing any signs of giving up on censorship," said Jonathan Zittrain, co-founder of Harvard Law School's Berkman Center for Internet and Society. "If anything, they're innovating and exploring other avenues."
Rumors abounded that Monday's Great Firewall outage was caused by maintenance work administered by Internet provider China Unicom.
China Unicom did not respond to requests for an interview. Neither did Chinese officials overseeing online security. It was unclear if all of China experienced the outage or just some regions.
Chinese authorities have been ramping up Web censorship for months. Primary in this push is a crackdown on pornography. But critics claim that effort is just a cover for tightening controls on the world's largest Internet community.
Authorities announced last week that 5,400 people were arrested last year for crimes related to online porn, though they did not say how many were charged.
Hundreds of websites have been shut down, including file-sharing destinations for pirated movies and music, as well as personal blogs.
One government ministry released a pronouncement last month that the local press interpreted to mean that foreign websites may one day have to register with the government before being allowed inside the Great Firewall.
As part of a new decree to screen out smut, individuals have been banned from registering personal websites using China's national domain name: .cn. The address is reserved for government entities and registered businesses.
In China's restive Xinjiang province, Internet access has been blocked since July, when deadly ethnic riots erupted in the capital of Urumqi. Residents in the region have access to only two websites, both run by state media.
However, the most sweeping proposal for Internet controls last year, a government plan to install filtering software called Green Dam Youth Escort on all computers sold in China, was shelved indefinitely in response to widespread criticism.
Nicole Liu in The Times' Beijing bureau contributed to this report.