How browser fingerprinting works
On a visit, the site receives values such as the User-Agent and accepted languages. JavaScript can then query browser APIs and send more details about the device and its rendering behavior. The site combines these values into a profile or hash and compares it with later visits.
Unlike a cookie, a fingerprint is inferred again rather than read from a stored identifier. Matching is probabilistic. Similar devices can produce the same result, while browser updates, settings and hardware changes can alter it.
Signals a fingerprint uses
- Software: browser version, operating system and supported features.
- Display and hardware: viewport, screen size, color depth, touch support and logical processor count.
- Rendering: Canvas, WebGL and AudioContext output affected by graphics hardware, drivers and software.
- Locale and configuration: timezone, language, font availability and accessibility preferences.
Services may pair these values with TLS fingerprinting. A TLS fingerprint comes from the connection’s ClientHello pattern, not from JavaScript browser APIs.
Browser fingerprint vs cookies and IPs
| Method | Source | Changes when |
|---|---|---|
| Browser fingerprint | Browser and device traits | Software, settings or hardware changes |
| Cookie | Stored site identifier | Cleared, blocked or expired |
| IP address | Network connection | Network or proxy changes |
A site can use a returned cookie as a stable identifier for that browser profile, but the cookie does not prove the identity of the browser, device or user. A fingerprint estimates whether two visits came from the same client. Sites often correlate all three signals.
Why it matters with proxies
A rotating proxy changes the IP address a website sees. It doesn’t change JavaScript results, display properties or normal browser headers. If one stable fingerprint appears from many IPs within a short period, a site may associate those requests.
Location mismatches can also affect a risk score. For example, an IP in one country paired with a distant timezone may look unusual, though legitimate travelers can create the same mismatch. Fingerprinting is only one input to bot detection; request rate, cookies and account history also matter.
Working with fingerprinting responsibly
- Use a current, standard browser that supports the site’s expected features.
- Keep one coherent browser profile and cookie jar through a related session.
- Don’t cycle fabricated values between requests. Contradictory settings can break pages and make a client more distinctive.
- Slow down when rate-limited and follow the site’s terms and robots.txt rules.
FAQ
Can a proxy hide my browser fingerprint?
Not by itself. A proxy changes the IP address the website sees, but browser and device signals usually remain the same.
Does incognito mode stop browser fingerprinting?
No. Incognito mode does not save local browsing history after the private session ends and uses a separate, temporary cookie store. It still exposes many of the same browser, display and rendering properties.
Is my browser fingerprint unique and permanent?
Not necessarily. It may be distinctive enough to recognize repeat visits, but fingerprints can overlap between similar devices and change after browser, driver, hardware or settings updates.