Private browsing is a device-privacy feature, not an invisibility cloak.
That distinction mattered in a major 2019 study of adult websites, and it still matters in 2026. Chrome itself now explains plainly that Incognito does not prevent websites, the services embedded on those websites, employers, schools or internet providers from potentially observing activity.
What researchers found — in that 2019 sample
Researchers analyzed 22,484 adult websites and reported that 93% transmitted data to at least one third party. Google-linked services appeared on a large share of the sites, and Facebook-linked tracking appeared on a smaller but still meaningful share. The study also warned that URLs themselves could reveal sensitive interests.
Local privacy
Does not keep visited pages in local browser history after the session
Useful on a shared device.
Session cookies/site data are discarded when the private session ends
During the session, sites still need temporary data to function.
Starts signed out by default
If you sign into a service, that service obviously knows which account is using it.
Files remain
Private mode does not erase files you intentionally download.
Online anonymity
It does not hide your activity from the website
The server still receives a connection and request.
It does not hide activity from services embedded on the site
Analytics, advertising or other third-party resources may receive data depending on the site and browser protections.
It does not hide your IP address
Private browsing is not a network anonymization service.
It does not hide activity from the network operator
Employer, school or ISP visibility depends on the network and encryption, not on local history mode.
It does not protect you from malware
Mozilla explicitly notes that private browsing is not an anti-malware tool.
Use layers and understand their limits
Choose a browser with strong tracking protection, keep it updated, block unnecessary third-party trackers, avoid signing into unrelated accounts during sensitive browsing, and understand that a VPN changes who can see network traffic but does not stop the destination website from receiving your connection or eliminate browser fingerprinting. Stronger anonymity needs a different threat model than simply opening a private tab.
Private browsing answers one narrow question: what stays on this browser after I close it?
It does not answer: who on the internet can observe this session?
That difference is especially important when the sites themselves reveal sensitive health, sexual, financial or political interests.