No matter which browser you prefer—Chrome, Firefox, Edge, Safari, Opera, or any of the others—it will almost certainly offer an incognito or private mode, one which ostensibly keeps your web browsing secret. (Google Chrome still shows a hat-and-glasses icon when you go incognito, as if you’re now in disguise.)

Incognito or private mode does indeed keep certain aspects of your browsing private, but it’s important to be aware of what it hides and erases from your computer or phone and what it doesn’t. Once you understand exactly what these modes do in your browser, you’ll know when they can be most useful.

What Incognito Mode Does

Perhaps the easiest way to think about incognito mode is that as soon as you close the incognito window, your web browser forgets the session ever happened: Nothing is kept in your browsing history, and any cookies that have been created (those little bits of data that log some of your actions online) are promptly wiped.

Cookies are what keep items in your Amazon shopping cart even if you forget about them for days, for example, and they also help sites to remember if you’ve visited them before—which is why you normally only get pestered to sign up for a site’s newsletter the first time you arrive. You might notice if you visit all your favorite sites in incognito mode, you won’t get recognized, and are then asked to sign up for a whole load of newsletters and special offers all over again.

This sort of anonymity is what incognito mode is good at—it’s like starting again with a blank slate, for better or for worse. Try loading up Twitter or Gmail, and these sites won’t automatically log you in as they normally do. For the same reason, incognito mode can sometimes be a handy way of accessing more free articles from a paywalled site (the site won’t instantly identify you as someone who’s been before, although many paywalled sites use other methods to figure that out).

Your browser won’t remember where you’ve been, what you’ve searched for, or the information you’ve filled into web forms while you’ve been in incognito mode—it’s as if Chrome, Firefox, or whatever browser you’re using has its back turned until you close down the incognito mode again.

With browsers now so personalized, you’re probably familiar with your frequently visited websites appearing as you type into the address bar or search box. Anything you’ve visited or searched for while in incognito mode shouldn’t appear in these suggestions (with a few caveats, as we’ll mention below). You’ll notice in some browsers that you can’t pull the normal trick of reopening a tab you’ve just closed while in incognito mode—your browser has already forgotten that you ever opened it in the first place.