In the letter, the employees said they were joining Amnesty International in calling for an end to the project. The rights organisation is running a campaign at Google offices around the world to protest against the project.
The news that Google plans to re-enter China — the company had a censored search engine in operation from 2006 to 2010, but pulled out when its servers were hacked by Chinese authorities — surfaced on 1 August in The Intercept.
There have been numerous developments since then, with even US Vice-President Mike Pence calling on the company to scrap the project.
GOOGLE MOTTOS: A HISTORY— MGK Hockey 1234 (@mightygodking) 28 March 2018
1999: Don't Be Evil
2003: Try Your Hardest To Not Be Evil
2008: Make A Reasonable Effort To Avoid Being Evil
2013: What Is Evil, Really, When You Get Down To It, I Mean Really
2018: *just a series of high-pitched giggles*
The employees said in their letter that their opposition was not targeted at China, but "we object to technologies that aid the powerful in oppressing the vulnerable, wherever they may be".
They said Dragonfly, if implemented, would send a message to other similar regimes that would make it harder for Google to deny them similar restrictive features.
"Our company’s decision comes as the Chinese Government is openly expanding its surveillance powers and tools of population control," they wrote.
"Many of these rely on advanced technologies, and combine online activity, personal records, and mass monitoring to track and profile citizens.
"Reports are already showing who bears the cost, including Uighurs, women’s rights advocates, and students.
"Providing the Chinese Government with ready access to user data, as required by Chinese law, would make Google complicit in oppression and human rights abuses."
The employees said they had joined Google because they believed the company was willing to place its values above its profits.
"After a year of disappointments including Project Maven, Dragonfly, and Google’s support for abusers, we no longer believe this is the case. This is why we’re taking a stand," they said.