Websites are still able to detect when a visitor is using Chrome's Incognito mode, despite Google's efforts last year to stop tracking.
There are several reasons why website administrators wish to block users who use the incognito mode feature.
For example, some users use incognito mode to bypass content paywalls and various content filters/restrictions. Additionally, current incognito mode (private browsing) features in most browsers come with aggressive anti-tracking capabilities that prevent websites from tracking their traffic.
Both issues – and the inherent use of private browsing – result in direct financial losses to websites and are the primary reasons why scripts that detect incognito mode operations have become popular in recent years.
Google tried to fix it in 2019
In early 2019, Google decided to take a stand against these scripts. Chrome 76, released in July 2019, included an update that blocks websites from using the FileSystem API to detect whether a user is using Chrome's regular browsing mode or incognito mode.
Before Chrome 76, the FileSystem API was simply not available in incognito mode, and website operators only had to query this API to find out if a user was using incognito mode. With Chrome 76, Google enabled the FileSystem API for incognito windows, rendering previous tracking scripts useless. However, this update was not foolproof. Google did not fully enable the FileSystem API, but simply set a limit on the amount of storage that incognito windows could access, at 120 MB.
It took developers over a week after the release of Chrome 76 to discover what was happening and develop scripts that probed the FileSystem API to determine the amount of storage a website could access and indirectly detect whether the user was using incognito mode or not.
Two different scripts were released in August 2019 [1, 2] and one of them even made it to the New York Times, confirming how popular these scripts are on news websites.
No new patches
Google promised in August 2019 to fix the bypass and block incognito mode detections.
However, nine months later, it is still possible to detect incognito mode in Chrome and all other Chromium-based browsers , such as Edge , Opera , Vivaldi, and Brave, which share the core Chrome codebase.
Additionally, developers have taken the scripts shared last year and extended support to browsers like Firefox and Safari, allowing websites to block users in incognito mode.
At this time, there is no deadline for a new Chrome update to block incognito mode tracking.
