China's campaign to stamp out technology that allows web surfers to evade its internet filters is disrupting work and study for entrepreneurs, scientists and students.
The crackdown comes as the ruling Communist Party tightens political control ahead of a congress at which President Xi Jinping is due to be appointed to a second five-year term as leader.
After Beijing began clamping down on use of VPNs in January, dozens of activists and lawyers have been detained and a cybersecurity law tightened control on online data.
How many people might be affected is unclear, but consumer research firm GlobalWebIndex says a survey of Chinese web surfers this year found 14 per cent use a VPN daily. For China's online population of 731 million, it means 100 million regular users.
Astronomers and physicists use services such as Google Scholar and Dropbox, accessible only via VPN, to share research and stay in touch with foreign colleagues.
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Merchants use Facebook and other blocked social media to find customers. Students look for material in subjects from history to film editing on YouTube and other blocked sites.
Control over information is especially sensitive ahead of October's twice-a-decade ruling party congress at which President Xi Jinping is due to be named to a second five-year term as leader.
The VPN crackdown is part of a campaign to tighten political control that activists say is the most severe since the 1989 suppression of the Tiananmen Square pro-democracy movement.
