BEIJING — Can Chinese censors vanquish the umbrella?

As protesters in Hong Kong continue to defy the authorities with their demands for greater democracy, mainland China’s politically minded web users have been trying to outmaneuver the invisible army of Internet guardians working to scour social media of photos and news about the continuing demonstrations.

They have been posting pro-democracy remarks on nonpolitical websites and uploading selfies of their shaved heads to express solidarity with the protesters. On Tuesday, some social media users shared stock images of President Xi Jinping carrying an umbrella, a not-so-subtle nod to that essential protester accessory for staving off sun, rain and pepper spray. Other users simply changed their profile photo to that of an umbrella.

Charlie Smith, co-founder of Greatfire.org, a group that tracks Internet censorship in China, said authorities were not likely to relax. “They are going to be on top of this situation 24/7.”

But there were signs Tuesday that China’s formidable censorship machine was struggling to keep up with savvy commenters who found ways to thumb their noses at the authorities.