What does incognito or private browsing actually do?

Private browsing does exactly one thing well and is believed to do several things it does not. The gap between the two is where people get caught out, and it is worth being precise about.

Safety

Step by step

1. Know what it actually prevents.The browser does not save history, cookies, site data or form entries from that session. When you close the window it discards them. That is the complete list.
2. Know who can still see your activity.The websites you visit, your internet provider, your employer or school if you are on their network or device, the network owner on public wifi, and anything installed on the machine. None of them is affected.
3. Understand it does not hide your IP address.Every site sees where the connection comes from exactly as it would normally. If that is what you want, a VPN or Tor is the tool, and each has its own trade-offs.
4. Understand it does not stop tracking within a session.Sites can still identify you across the session through fingerprinting, and if you sign in to anything you have identified yourself completely. Signing into an account in private mode defeats most of the point.
5. Use it on a shared or public computer.This is what it is for. Nothing is left in the history, no cookies persist, and no saved passwords are offered. Still sign out properly, and still close the window when you finish.
6. Use it for a second account.A private window is a clean session, so you can be signed into two accounts on the same site at once. Genuinely useful and completely unrelated to privacy.
7. Use it to see a site as a stranger sees it.No cookies, no personalisation, no login. Useful for checking prices, seeing what a page looks like to someone who is not signed in, or testing something you have just published.
8. Do not rely on it for anything sensitive on a work device.Monitoring software on a managed device records activity regardless of the browser mode. The same applies to a school or family device with monitoring installed.
9. Remember downloads and bookmarks persist.Anything you download stays on the machine, and any bookmark you make is saved. The session is discarded; the files are not.
10. Close the window to end it.The data is discarded when the private window closes, not when you navigate away. Leaving a private window open indefinitely keeps the session alive.

Tips

• If you want the site not to recognise you, the reliable version is a private window plus not signing in. Signing in is what identifies you, not the cookies.
• Browser profiles are better than private mode for permanently separating work and personal browsing, because they keep history and passwords separately rather than discarding them.
• If the concern is other people on your own computer, separate user accounts are a better answer than remembering to open a private window.

Common mistakes

• Treating private browsing as anonymity — It hides activity from the next person to use the device and from nobody else. Your provider, employer and every site you visit see exactly what they always would.
• Signing into an account in a private window and expecting privacy — Signing in identifies you directly. The absence of cookies is irrelevant once you have told the site who you are.

Questions people ask