Google Chrome’s Incognito Mode is based on the principle that you should have the choice to browse the web privately. At the end of July, Chrome will remedy a loophole that has allowed sites to detect people who are browsing in Incognito Mode. This will affect some publishers who have used the loophole to deter metered paywall circumvention.
Private browsing principles
People choose to browse the web privately for many reasons. Some wish to protect their privacy on shared or borrowed devices, or to exclude certain activities from their browsing histories. In situations such as political oppression or domestic abuse, people may have important safety reasons for concealing their web activity and their use of private browsing features.
Google want you to be able to access the web privately, with the assurance that your choice to do so is private as well. These principles are consistent with emerging web standards for private browsing modes.
Closing the FileSystem API loophole
Today, some sites use an unintended loophole to detect when people are browsing in Incognito Mode. Chrome’s FileSystem API is disabled in Incognito Mode to avoid leaving traces of activity on someone’s device. Sites can check for the availability of the FileSystem API and, if they receive an error message, determine that a private session is occurring and give the user a different experience.
With the release of Chrome 76 scheduled for July 30, the behavior of the FileSystem API will be modified to remedy this method of Incognito Mode detection. Chrome will likewise work to remedy any other current or future means of Incognito Mode detection.