Google Will Make It Harder For Sites To Block Chrome’s Incognito Mode

Google is looking to fix an age-old loophole that allows websites to check to see if a user is in Incognito mode when visiting the site with the Chrome browser.

When using Incognito mode, browsing history is not recorded, and websites cannot use cookies to track internet activity. Since so much of the internet uses tracking cookies to target users with ads, some sites don’t like users visiting in this privacy mode, and will block them. To see examples of this, try viewing articles on MIT Technology Review website while using Incognito.

How it works

According to Chrome, the most common way that websites detect the mode is by trying to call the “FileSystem” API, which is available in Chrome’s default mode. This API is disabled in Incognito since it can create a permanent record hence defeating the purpose of private browsing. So if a website tries to access the API, Incognito will throw an error, which triggers the site to display its “turn off Incognito” message.

Since there’s no adoption of the FileSystem API by other browser vendors, it appears to be only used by sites to detect incognito mode. By making this harder, hopefully the overall usage of the API goes down to the point that we can deprecate and remove it.

Google Chrome developers say they plan “to add a virtual file system in RAM to Incognito mode”. This way when websites (that forbids you to access its site with Incognito) “call the FileSystem API”, they won’t get an error, and when the user closes the Incognito window, the “virtual file system disappears leaving no trace”. Its not yet known when the feature will be rolled out but when it does, users will have to apply the flag #enable-filesystem-in-incognito to enable the feature.