Google is sued in the US for allegedly tracking users' "private" browsing
The company said it is upfront about the data being collected.
Google has been sued in the US over claims it illegally tracked people even when they were browsing in "private mode".
The class action lawsuit is seeking at least $5 billion as it accuses the Alphabet Inc unit of collecting information illegally about what users are viewing online, even when using Google's "Incognito Mode".
Some users believe that their search history is not being tracked when using Incognito Mode, but Google say this is not the case.
Google said this is not illegal and it is upfront about the data being collected in this mode.
Google spokesperson, Jose Castaneda, said the California-based company will defend itself vigorously against the lawsuit.
"As we clearly state each time you open a new incognito tab, websites might be able to collect information about your browsing activity," he said.
The lawsuit, filed in US District Court for the Northern District of California, said that Google uses other tracking tools it provides to website publishers and advertisers to keep track of what websites people visit.
"Billions of times a day, Google causes computers around the world to report the real-time internet communications of hundreds of millions of people to Google," according to the complaint filed.
The complaint argued the company "cannot continue to engage in the covert and unauthorised data collection from virtually every American with a computer or phone".