Chrome’s Incognito mode allows users to access websites more privately than the usual browser, by not storing information such as browsing history, and cookies and site data.
To do this Google disables some background features, such as one called the FileSystem API which avoids leaving traces of activity on someone’s device.
However, websites are able to check the availability of FileSystem API, and if they receive an error message back, determine that the person is using Incognito mode, and provide them a different experience.
This feature could be used by publishers to work out when people are trying to dodge paywalls.
Some news websites offer a limited number of free articles, before telling users they need to subscribe, but people could try going through Incognito to essentially reset their count and access more articles for free.
Google claims the change is necessary to protect people under political oppression or subjected to domestic abuse, who may have important safety reasons for concealing their web activity.
“We suggest publishers monitor the effect of the FileSystem API change before taking reactive measures since any impact on user behaviour may be different than expected and any change in meter strategy will impact all users, not just those using Incognito mode,” the company said.
“Our News teams support sites with meter strategies and recognise the goal of reducing meter circumvention, however any approach based on private browsing detection undermines the principles of Incognito mode.”