Google is closing a loophole within the Chrome web browser that enables websites to detect whether visitors are using the Incognito Mode.
The company says the tactic, which exploits the FileSystem framework, goes against the spirit of private browsing, which could be enabled by users for a number of very good reasons. As a result, that loophole will be slammed shut in Chrome 76, which is coming later this month.
Currently, sites can check for the availability of the FileSystem API, which is disabled in Incognito Mode. If the site receives an error message they know the privacy-protecting mode is enabled. Crafty.
Many publishers use this to detect whether readers are trying to circumnavigate metered access to paywalls, which often give users a certain amount of free articles per month before they have to pay to subscribe. If sites detect the Incognito Mode is enabled they often throw up the paywall.
Google says that as well as closing this loophole, it’ll also do more to prevent future attempts to get to users who’ve chosen to browse the web privately.
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It says sites affected by the change can reduce the number of free articles, and ask users for a log-in to read any content. The company also suggests the publishers could be more generous with free content in order to develop good will with potential subscribers. That’s unlikely to go over well.
In a blog post, the firm says: “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.
“We 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.”