Why "Incognito mode" is not what you think it is

A private window is a janitor, not a disguise. When you close the tab, it tidies up after you on your own machine — no history, no cookies, no autocomplete entry. It does not change what your network sees, what the website logs, or what your browser fingerprint looks like. The name is doing a lot of work, and most of it is misleading.

This is not pedantry. People genuinely use private mode believing it provides anonymity from their employer, their school network, or the website they are visiting. None of that is what private mode is for, and assuming otherwise is how people get into trouble. So let us walk through what it actually does, browser by browser, and where it earns its keep.

What "private mode" actually does, in one paragraph

Across every mainstream browser, private mode does roughly the same three things. It opens a session with no cookies. It does not write history, autocomplete, or download list entries to disk for that session. And it discards cookies and site storage when the window closes. That is essentially the entire feature. Everything else is window dressing or vendor-specific seasoning.

What it does not do

• Hide your traffic from your ISP. The DNS lookups still happen, the TLS handshake still names the host, and the IP destination is unchanged.
• Hide your traffic from your employer or school network. Network monitoring tools see the same metadata they would see otherwise, plus any TLS-inspecting middlebox sees the inner request.
• Hide you from the website. The site sees your IP, your User-Agent, your full browser fingerprint, and any logged-in session you create during the visit.
• Hide you from extensions. Most browsers run extensions in private windows by default if you have allowed them to. They can still read every page you visit.
• Stop trackers. Third-party tracking via fingerprinting works identically. The cookies are session-scoped, but the canvas hash is the same.
• Stop malware. A drive-by download is just as effective in a private tab as in a normal one.

Browser by browser

Chrome (Incognito)

Discards cookies, history, and form fill on close. Disables extensions by default, though most users re-enable their ad blocker, which negates the isolation. Since the 2024 settlement, the disclosure now explicitly says websites, your employer, and your ISP can still see your activity. Third-party cookies are blocked by default in Incognito, which is the strongest functional benefit.

Safari (Private Browsing)

Same baseline behaviour. In Safari 17 and later, Private Browsing locks tabs behind Touch ID or Face ID after a period of inactivity, which is a thoughtful concession to shared devices. It also enables Apple's Intelligent Tracking Prevention more aggressively and, on iOS, routes some traffic through iCloud Private Relay if the user has subscribed. That last bit is the closest any private mode comes to actual network privacy, and it only applies to Safari.

Firefox (Private Browsing)

Same baseline. Firefox additionally enables Total Cookie Protection by default in private windows, which partitions cookies per top-level site so a tracker on site A cannot read its cookie on site B. This is a meaningful tracking defence and is also available outside private windows on recent versions.

Brave (Private window, and Private window with Tor)

Brave ships two flavours. The default Private window is similar to Firefox's, with stricter fingerprinting protection inherited from Brave's normal mode. The second, "Private window with Tor", actually routes that window's traffic through the Tor network. It is not Tor Browser — the fingerprinting hardening is weaker than Tor's — but it is the only mainstream "private mode" feature that genuinely changes what your network sees. Use it for the use cases where you would otherwise reach for Tor Browser briefly.

When private mode genuinely earns its keep

1. 1Shared devices. A library terminal, a hotel computer, a friend's laptop. Private mode keeps your session out of the local profile.
2. 2Signing into a second account. Logging into a work Gmail in a private window without disturbing your personal session is the classic use case, and it works perfectly.
3. 3Comparison shopping. Some travel and retail sites adjust prices based on cookies and prior visits. A clean session occasionally surfaces a different price.
4. 4Reading paywalled articles. Increasingly defeated, but still works on a surprising number of metered paywalls.
5. 5Sanity-checking your own site. Web developers test logged-out states in private windows constantly. It is the original use case.

When it is security theatre

Anything network-level. If the person you are hiding from sits between your browser and the internet — your ISP, a corporate proxy, a campus firewall, a captive portal at an airport — private mode does nothing. It is, by design, a local-machine feature.

Anything fingerprint-level. We have written a separate post on browser fingerprinting; the short version is that your private window draws the same canvas, runs the same audio test, and reports the same fonts as your normal one. A determined tracker correlates the two trivially.

The right tool stack

For local privacy on a shared device, private mode is the right tool. For network privacy from your ISP or a hostile Wi-Fi, you need a VPN. For tracker resistance, you need a browser that takes fingerprinting seriously — Brave, Firefox with resistFingerprinting, or Tor Browser. For genuine anonymity, you need Tor Browser, full stop, and you need to be careful about what you do inside it.

These are different layers and they solve different problems. A VPN protects the network leg. Private mode protects the local leg. A fingerprint-resistant browser protects the application leg. People run into trouble when they assume one of these solves all three. We say this often because the misunderstanding is genuinely common, and the cost of getting it wrong is the small but real category of incidents where someone trusted a private window to do something it never claimed to do.

A useful mental test

Before opening a private window, ask: who am I actually trying to hide from? If the answer is "the next person to use this laptop", you are in the right place. If the answer involves any party that sits on the network or runs the website you are about to visit, you need different tools. PlanetProxy is one of those tools. So is Brave. So, for the deep end, is Tor. Private mode is a real feature with a small, honest job. Treat it as such and it will not let you down. Treat it as a cloak and it will.