What Your Web Browser's Incognito Mode Really Does
This tool can be useful as long as you understand its limitations
You don’t have to be a computer whiz to grasp the value of private browsing.
At a time when consumers are worried about sensitive information falling into the wrong hands—including the websites they go to and the content they view—it’s nice to have a browser tool that conceals some online activity.
All of today’s major web browsers—Google Chrome, Microsoft Edge, Mozilla Firefox, and Apple’s Safari—offer a feature that provides a private browsing window and deletes the browsing history on your device after you close it.
How Does Incognito Mode Work?
Generally speaking, when you browse the web in a regular, non-incognito window, your browser stores the web address, also known as the URL, of every page you go to and keeps that data even after you close the window. That makes it easier for you to retrace your steps and find the same pages again later on.
The browser also stores cookies, which are small files that websites and advertisers embed in websites.
The next time your browser loads a page with elements (as little as a single pixel) from a company’s servers, the information is sent back.
Cookies have a lot of functions, such as letting you go to password-protected sites without having to manually log in every time. They’re used to keep track of any items you place in a commerce site’s shopping cart, letting you fill the cart now and check out later. Cookies also let big advertisers, such as Google’s DoubleClick, track you across the web.
Incognito windows work differently.
Here, all of those cookies are deleted from your browser after you close the incognito window. Browser history isn’t saved, either, so if someone else uses that computer, smartphone, or tablet, it will not list the web pages you just went to. This can be useful if you share a device with roommates or live at home with your parents. It’s even more so if you’re searching for ways to escape domestic abuse.
Another benefit: You may notice less tracking from advertisers.
If you search for a product—blenders, say—in a private window, you’re not as likely to see cooking supplies show up in web ads over the next few days.
Some browsers, including Firefox and Safari, also protect against fingerprinting, a technique employed by data collectors to identify you and track you across the web by using a collection of variables such as your IP address, which browser version and operating system you use, and which graphics card you have installed.
Why Is Incognito Mode Useful?
Despite some limitations, incognito mode may be useful in a variety of situations.
Let’s say you’re shopping for a gift for your spouse on the family laptop—maybe a day pass for a local spa. Using incognito mode will prevent anyone else who might later use that laptop after you’re done from seeing that you searched for “best spas near me.” And because any cookies that might be generated by your search are deleted as soon as you close the window, you’re unlikely to see ads for spas pop up over the following days in that browser.
Other somewhat “low stakes” cases for incognito mode may include looking at someone’s LinkedIn profile without the person finding out about it; checking the score of last night’s Yankee game without triggering all sorts of baseball-related alerts and notifications on your Android smartphone; or taking a quick gander at the latest celebrity gossip without condemning yourself to a future of nonstop pop culture nonsense filling up your feeds.
Incognito mode will also prove handy if you need to log in to your email account at, say, a public library or office supply store, perhaps to print out some documents if you don’t have a printer at home. As soon as you close the window, your information is zapped from that browser forever. We still recommend logging in to sensitive accounts from your home if at all possible, but incognito mode is a good plan B.
What Doesn't Incognito Mode Do?
Once you close an incognito window, most of the data about your web session will be deleted, but this only covers data that would have been saved locally on your device, such as cookies. Any data that may have been stored on the servers of the websites themselves won’t be affected by your use of incognito mode.
In other words, using incognito mode won’t erase the records of your visit from a website’s servers or from any networks you went through to get to a site. Crucially, this means that if you go to a website while connected to your employer’s WiFi network while using incognito mode, your company will know which sites you’ve visited. Depending upon your company’s policies, you may want to keep your Facebook, Twitter, or ESPN.com habit to yourself at your home.
Put another way, if it isn’t safe for work, then you shouldn’t go there even while in incognito mode.
Incognito mode also doesn’t do anything to protect you from malware. For that, you’ll want to take other steps, such as ensuring that your software is fully up to date with the latest security patches. (It’s best to make sure you have automatic updates enabled.) And while the latest versions of Windows and macOS do include robust anti-malware capabilities built into them, you might also want to consider using a trusted piece of dedicated anti-malware software.
Lastly, know that any files you download while using incognito mode will remain on your device even after you close the window. If you’ve downloaded a sensitive file that you don’t want the next person who uses the device to find, be sure to delete it and then empty the Recycle Bin (Windows) or Trash (macOS).