This is sold as protecting your privacy by keeping your browser or website from tracking your activity. While incognito mode does do this, it has distinct limitations. Here are some things to bear in mind.

Why is incognito mode useful?

Incognito mode is definitely useful for many personal and business purposes. Here are some of the things it lets you do:

  1. Log into a website as two different accounts at the same time, such as your personal Facebook and your company Facebook, two different Gmail accounts, etc. Many websites are designed to keep you logged in in all windows, and incognito mode gets around that.
  2. Avoid personalized advertising, either all the time, or when you are doing specific activities. For example, if you know visiting a certain site will have you inundated with ads, you can go to that particular site in private mode.
  3. Allow you to check what your own website looks like when logged out, without having to log back out and back in.
  4. Check your search engine rankings without “personal results” getting in the way, and with no search history. This can help marketers establish whether they are getting the page rank they need from their latest campaign.
  5. Quickly make sure you are not being shown a cached version of a website, as private mode does not access the standard browser cache. This can also help determine whether a website is inaccessible, as sometimes caching can make things look to be up when they are not.
  6. When using somebody else’s computer, it keeps you from messing with their accounts and keeps them from knowing what you did. For example, if you want to access Facebook from a relative’s computer while staying with them, private mode is handy so they don’t have to log out, and so that you don’t inadvertently leave it logged on as you. Private mode also doesn’t leave cookies (unless you use one specific browser) cluttering somebody else’s system.
  7. If you are starting a research project, private mode can be used to make a fresh start, without search engines pulling up the results from the last project. This can significantly reduce clutter and help you get to the results you want faster.
  8. If you are logging in to a public computer, using private or incognito mode guarantees that you will be completely logged out when you close the session, ensuring you don’t forget to log out. It also makes it harder for the next user of that computer to see what you were doing. They will actually have to make an effort.

What does it not do?

Private mode is often sold as the easiest way to stay safe online. In many ways it is. As it is built into the browser, it is easy to use. It costs nothing, and it doesn’t require you to install a client. It also doesn’t noticeably slow down your connection. It is available on any computer you might use, whether it is a library computer, your friend’s computer, or a public terminal.

However, private mode has a number of limitations:

  1. It does not obscure your IP from websites. Although it sends “do not track” signals, this may not always be respected. Any competent hacker can still get your IP easily enough. The one exception is Opera, which has a built-in partial VPN system. However, Opera’s own servers can be used to snoop.
  2. The Microsoft Edge browser, specifically, still uses your stored cookies, which removes much of the utility and much of the protection from private mode. All other browers access a separate cookie store which is erased when you close the session.
  3. Private mode does not affect tracking performed by websites you are logged into, or personalized ads served based off of that. Many websites still store your activity history for that site specifically once you have logged in.
  4. It does not block tracking done by your own router or by any proxy servers you are using. Note that proxy servers often do track your activity and can even insert their own ads.

When is private mode a good idea?

Private mode has a few advantages over more secure systems:

  1. You don’t have to install anything, meaning it can be used on library, hotel, and other public computers. In fact, you should always use private or incognito mode if you use a public computer or one belonging to somebody else.
  2. As mentioned above, it has some utility not provided by proxies or VPNs, particularly if you use the internet extensively for research or are a website administrator.

When is it not a good idea?

Incognito or private mode alone should not be used to:

  1. Perform financial transactions on public computers. You should always avoid doing so unless it is an emergency of some kind. It is safer to use your mobile device connected to a trusted VPN, and even then bear in mind that public wi-fi is always vulnerable to man-in-the-middle attacks (somebody reading the traffic and either getting hold of your data or inserting malware). Thinking private mode makes you safe can make you vulnerable to keyloggers or a public computer that is riddled with malware. It is, however, better than not using private mode.
  2. Do sensitive business over public networks. Again, you want to use a VPN any time you are handling sensitive information. Incognito mode alone is not going to keep you safe.

Browser manufacturers tend to tout private mode as a great addition to your security. While it certainly has its uses, you should not rely on a “private window” to keep you safe from malware and tracking online.

Instead, use private windows for the things they are useful for, such as checking your Google ranking or keeping you from forgetting to log out of secure websites, whilst choosing a more robust security solution such as a proper VPN.