Most modern browsers offer a feature called “privacy mode.” It is touted as a privacy feature, though there are caveats and limitations. It is very useful, though, for troubleshooting web site or browser issues.
What is Private Browsing?
Google Chrome calls it incognito window, Mozilla Firefox refers to it as private window, and Apple Safari calls it a privacy mode. Even though they use different names, each is doing essentially the same thing. Privacy mode ignores pre-existing cookies and cache files and puts the new files into a temporary space that is deleted as soon as the private browsing session is closed.
Private browsing as a troubleshooting step
Private browsing gives you a “fresh start” with a web page in case something has gone wrong. Errors and misconfigurations held in cookies or cached files will no longer apply. It’s also why this mode is helpful! Instead of having to clear your browser cache, which can involve wading through several layers of settings windows, you can open a new “private” window and achieve the same effect.
Experts only: What is meant by “private”
Once you’re done browsing in the private window, you can just close it. All information about that session is discarded. However, there are some important caveats to this:
information stored server-side is unaffected, IP-based tracking techniques can still identify a computer using private browsing.
some browser plugins (notably Flash) do not properly honor privacy mode.
For these reasons, do not treat privacy mode as complete privacy -- it just prevents some information being stored on the computer being used at the time.
For more information, find the original LTS post here.