China's Internet control software, called "Green Dam", has sparked international and domestic concerns, but the real challenge may be the nation's own PC market.
From Wednesday the government is ordering all PCs sold in China to have the filter, intended to block obscene images, but which critics say is aimed at deterring political dissent.
The move is the latest Communist Party initiative to control the Internet, which has about 300 million users in China.
Last week a Chinese official accused Google of spreading obscene content over the Internet, and the comments came a day after Google on-line services abruptly became temporarily inaccessible to many mainland users.
But some see China's own PC and software market as the main difficulty ahead for the government.
The freewheeling Chinese IT and retail market, known for years as a source of pirated software and black market DVDs, may end up frustrating censors, as the software is stripped out and efforts to circumvent the order emerge.
Beyond the streets of Beijing, foreign critics say the software is technically flawed and could be used to spy on Internet users, as well as to block sites.
Corporations and international trade officials have urged Beijing to reconsider or delay the controversial filter that will be pre-installed in all PCs, with some expecting the lodging of a formal complaint with the World Trade Organization.
Kitty Bu reporting for Reuters in Beijing.