Privacy has always been a constant concern for many people. Internet users are often worried about the browsing information that is left on their storage media. Web browsers were later introduced with a new feature called private browsing to overcome this issue. The private browsing mode is expected to behave as normal browsing session but without storing any data such as browser cookies, history, cache and passwords on the local machine. Unfortunately, previous researchers concluded web browser often failed to provide the intended privacy protection to their user. Along the way of this reviewing process, the weakness and downside of previous web browser vendors have been identified.