Furthermore, there is a possibility that identifiable traces of activity could be leaked from private browsing sessions by means of the operating system, security flaws in the browser, or via malicious browser extensions, and it has been found that certain HTML5 APIs can be used to detect the presence of private browsing modes due to differences in behavior. Private browsing modes do not necessarily protect users from being tracked by other websites or their Internet service provider (ISP). In web development, it can be used to quickly test displaying pages as they appear to first-time visitors. These modes are designed primarily to prevent data and history associated with a particular browsing session from persisting on the device, or being discovered by another user of the same device. Browsing history is not saved, and local data associated with the session, such as Cookies, Web cache, are cleared when the session is closed. When operating in such a mode, the browser creates a temporary session that is isolated from the browser's main session and user data.

Private browsing is a privacy feature in some web browsers. The start page for private browsing mode in Firefox.

Google chrome incognito mode cache