What does incognito (private) browsing actually hide?

More context

Every major browser has the same feature under different names: Chrome calls it Incognito, Firefox calls it Private Browsing, Safari and Edge call it Private Browsing and InPrivate. They all do the same small list of things, and stop there.

What incognito does do:

• Your browser does not save the history of this session.
• Your browser does not keep the cookies set during this session — they are wiped when you close the window.
• Your browser does not store form entries or autofill from this session.
• Your browser does not write cached files to disk.
• Most browsers also do not store downloads in history, although the files themselves stay where you saved them.

What incognito does NOT do:

• It does not hide your IP address. Your home, café or office network sees the same outgoing connection.
• It does not hide DNS queries. Your ISP and your network operator see the same list of domains you visit.
• It does not hide you from the website. When you log in, you identify yourself; the site links the session to everything it already knows about you.
• It does not stop trackers. Cookies are gone after the session, but fingerprinting (font list, screen size, time zone) still works perfectly inside the session.
• It does not hide you from monitoring software installed on the device itself — corporate MDM, parental-control apps, school-issued laptops.
• It does not protect against malware. Anything you download in incognito runs the same as anywhere else.

The accurate mental model: incognito is a setting on your browser, on this device, after you close the window. Everything that happens upstream of your browser — the network, the operating system, the websites, the advertisers — is unaffected.

Where it is genuinely useful:

• Shared devices. A guest using your laptop, a child borrowing your phone, browsing on a hotel-room computer — incognito stops them from inheriting your sessions and stops the device from remembering theirs.
• Logging into a second account. If you are already signed in to Gmail in a normal window and want to check a different Gmail account, an incognito window lets you do it without signing the first one out.
• Price-comparison and recommendation feeds. Booking sites and stores sometimes raise prices on return visits; an incognito window looks like a first visit.
• Embarrassment-free Googling. Birthday surprises, medical questions, things you do not want auto-completing later in your normal window. (Note: still visible to the network and to Google itself.)

Where people get burned:

• Using incognito to “browse anonymously” — it is not anonymous in any meaningful sense.
• Assuming the boss / school / ISP “cannot see” — they can see exactly the same as before.
• Logging into the bank on a public computer in incognito mode thinking that protects them — it protects the next person from seeing the session, but malware or a key-logger on that computer sees the password either way.

If you actually need to hide your network activity from the local network, you want a VPN. If you actually need anonymity (journalism, dissent, source protection), you want Tor Browser. Incognito is a useful, narrow tool — naming it well is most of the battle.