Google may be developing a special version of its search engine that would allow certain information to disappear in China. This would not be the first time a company has done so – and it would not be the first time Google has done so.

The decision has turned fresh attention to China's internet censorship regime, so wide-ranging that it has been labelled the "Great Firewall" and so powerful that it has allowed the government to ban people from using a single letter.

The suggestion that China could be partnering with the company, has been attacked by human rights campaigners and others, who suggested that Google relenting on censorship would be a "dark day", in the words of Amnesty International. Google would follow a whole host of companies, including LinkedIn, that already censor their users at the price of operating in China.

Gadget and tech news: In pictures Show all 25 1 /25 Gadget and tech news: In pictures Gadget and tech news: In pictures Gun-toting humanoid robot sent into space Russia has launched a humanoid robot into space on a rocket bound for the International Space Station (ISS). The robot Fedor will spend 10 days aboard the ISS practising skills such as using tools to fix issues onboard. Russia's deputy prime minister Dmitry Rogozin has previously shared videos of Fedor handling and shooting guns at a firing range with deadly accuracy. Dmitry Rogozin/Twitter Gadget and tech news: In pictures Google turns 21 Google celebrates its 21st birthday on September 27. The The search engine was founded in September 1998 by two PhD students, Larry Page and Sergey Brin, in their dormitories at California’s Stanford University. Page and Brin chose the name google as it recalled the mathematic term 'googol', meaning 10 raised to the power of 100 Google Gadget and tech news: In pictures Hexa drone lifts off Chief engineer of LIFT aircraft Balazs Kerulo demonstrates the company's "Hexa" personal drone craft in Lago Vista, Texas on June 3 2019 Reuters Gadget and tech news: In pictures Project Scarlett to succeed Xbox One Microsoft announced Project Scarlett, the successor to the Xbox One, at E3 2019. The company said that the new console will be 4 times as powerful as the Xbox One and is slated for a release date of Christmas 2020 Getty Gadget and tech news: In pictures First new iPod in four years Apple has announced the new iPod Touch, the first new iPod in four years. The device will have the option of adding more storage, up to 256GB Apple Gadget and tech news: In pictures Folding phone may flop Samsung will cancel orders of its Galaxy Fold phone at the end of May if the phone is not then ready for sale. The $2000 folding phone has been found to break easily with review copies being recalled after backlash PA Gadget and tech news: In pictures Charging mat non-starter Apple has cancelled its AirPower wireless charging mat, which was slated as a way to charge numerous apple products at once AFP/Getty Gadget and tech news: In pictures "Super league" India shoots down satellite India has claimed status as part of a "super league" of nations after shooting down a live satellite in a test of new missile technology EPA Gadget and tech news: In pictures 5G incoming 5G wireless internet is expected to launch in 2019, with the potential to reach speeds of 50mb/s Getty Gadget and tech news: In pictures Uber halts driverless testing after death Uber has halted testing of driverless vehicles after a woman was killed by one of their cars in Tempe, Arizona. March 19 2018 Getty Gadget and tech news: In pictures A humanoid robot gestures during a demo at a stall in the Indian Machine Tools Expo, IMTEX/Tooltech 2017 held in Bangalore Getty Gadget and tech news: In pictures A humanoid robot gestures during a demo at a stall in the Indian Machine Tools Expo, IMTEX/Tooltech 2017 held in Bangalore Getty Gadget and tech news: In pictures Engineers test a four-metre-tall humanoid manned robot dubbed Method-2 in a lab of the Hankook Mirae Technology in Gunpo, south of Seoul, South Korea Jung Yeon-Je/AFP/Getty Gadget and tech news: In pictures Engineers test a four-metre-tall humanoid manned robot dubbed Method-2 in a lab of the Hankook Mirae Technology in Gunpo, south of Seoul, South Korea Jung Yeon-Je/AFP/Getty Gadget and tech news: In pictures The giant human-like robot bears a striking resemblance to the military robots starring in the movie 'Avatar' and is claimed as a world first by its creators from a South Korean robotic company Jung Yeon-Je/AFP/Getty Gadget and tech news: In pictures Engineers test a four-metre-tall humanoid manned robot dubbed Method-2 in a lab of the Hankook Mirae Technology in Gunpo, south of Seoul, South Korea Jung Yeon-Je/AFP/Getty Gadget and tech news: In pictures Waseda University's saxophonist robot WAS-5, developed by professor Atsuo Takanishi Rex Gadget and tech news: In pictures Waseda University's saxophonist robot WAS-5, developed by professor Atsuo Takanishi and Kaptain Rock playing one string light saber guitar perform jam session Rex Gadget and tech news: In pictures A test line of a new energy suspension railway resembling the giant panda is seen in Chengdu, Sichuan Province, China Reuters Gadget and tech news: In pictures A test line of a new energy suspension railway, resembling a giant panda, is seen in Chengdu, Sichuan Province, China Reuters Gadget and tech news: In pictures A concept car by Trumpchi from GAC Group is shown at the International Automobile Exhibition in Guangzhou, China Rex Gadget and tech news: In pictures A Mirai fuel cell vehicle by Toyota is displayed at the International Automobile Exhibition in Guangzhou, China Reuters Gadget and tech news: In pictures A visitor tries a Nissan VR experience at the International Automobile Exhibition in Guangzhou, China Reuters Gadget and tech news: In pictures A man looks at an exhibit entitled 'Mimus' a giant industrial robot which has been reprogrammed to interact with humans during a photocall at the new Design Museum in South Kensington, London Getty Gadget and tech news: In pictures A new Israeli Da-Vinci unmanned aerial vehicle manufactured by Elbit Systems is displayed during the 4th International conference on Home Land Security and Cyber in the Israeli coastal city of Tel Aviv Getty

The special version, according to the accounts of those who have seen initial prototype, would work like the normal version of Google but cut out any problematic words or websites. Wikipedia would be inaccessible, for instance, with a little note making clear that some sites have been banned being visible in its place.

Google left the country in 2010, in protest to the censorship that the Chinese government demanded from it. That censorship is still in place – and growing.

But China's importance as a market for tech companies is growing too. That has put pressure on companies such as Google and its competitors, who face calls from shareholders to avoid giving up on revenue but want to ensure that the freedom of information is protected.

The vast and powerful sweep of China's internet censorship is probably best demonstrated in its more farcical and confusing moments. This year, for instance, the country entirely banned the use of the letter "N" from the internet.

It was a decision that prompted mockery and some confusion. But it showed how much power the government can have on discussion on the internet: it was banned because it was being used to talk about the term limits of Chinese president, in debating a plan to give Xi Jinping the power to rule the country indefinitely.

And even apparently innocent things can be eradicated from the internet. This year, Peppa Pig followed Winnie The Pooh in being banned in China, with videos being removed and discussions of the words all censored.

Being a tech company in China involves assenting to that kind of blocking, often leading posts to disappear entirely. LinkedIn participates in such censorship, for instance, while Facebook has been reported to be working on a tool that would allow it to automatically suppress certain problematic posts.

But the history of censorship in China will also serve as a warning to Google: even companies that acquiesce to Beijing and apply its restrictions, do not always succeed in getting into the country. Facebook, for instance, last month appeared to have finally won the right to operate in the country – and then had it promptly withdrawn.

That illustrated not just the power of the Great Firewall but the more traditional problems involved in running a technology company in China. Even if a company is happy to censor its users, it can be difficult for them to work out how exactly they are supposed to do so – the country is run by a decentralised government that operates at everything from a very local to a huge national level, and an intergovernmental dispute can be enough to knock even a pliable tech company out.