What Is Browser Fingerprinting? What Websites Can See
Learn how browser version, screen and device signals combine, how fingerprinting differs from cookies and what private browsing can change.
A combination of browser signals
Browser fingerprinting combines several properties instead of relying on a single serial number. Examples include languages, timezone, screen dimensions, operating system and exposed hardware hints. Similar devices may have different settings, while different people can share the same properties. A summary value is therefore not proof of identity. Browser updates and configuration changes can alter it.
How it differs from cookies and private browsing
A cookie is a small piece of data a website can store in the browser. Fingerprinting instead compares properties currently exposed by the browser, potentially without a dedicated cookie. Private browsing changes how local history and session data behave, but does not hide every device property. Opening a private window does not block every tracking method; built-in tracking protection and site permissions also matter.
Why some reported fields are missing
Browsers may reduce or omit version, memory and platform details. A Google Inc. vendor value does not prove someone uses Chrome: other Chromium browsers may report it too. Client Hints provides a structured subset of information in supporting browsers, while others may not implement it. An unsupported field does not mean the test is broken. These are reported signals rather than independently verified hardware records.
What the Astrotor test measures
The Astrotor tool computes a SHA-256 summary of basic visible signals on your device when you press the button. After you press GO, it also examines local canvas, WebGL, silent audio processing and a limited set of font signals. With no visitor comparison database, it cannot measure population uniqueness or give a definitive tracking-risk score. Comparing windows or devices can illustrate changes, but a match does not prove the same person and a difference does not prove a different person.
Reducing unnecessary exposure
Keep the browser updated, remove unnecessary extensions and grant camera, microphone or location access only where needed. Review built-in tracking protection; installing many extensions to spoof individual fields is not necessarily better. A VPN may change the network address but does not hide all browser properties. This tool processes its summary locally; the live site’s separate use of Analytics and AdSense is described in the privacy information.