Browser check
Every time you open a web page, your browser answers a number of questions about itself. This page asks them the way a tracking script would, shows you the answers and explains what each one is for.
What this shows about your browser
Your combined code:
This is the short code a script could compute from all the stable details below. If two sites computed the same code, they could tell it was the same browser without using a cookie. It is not an identity: it only says that this combination of details is what a script sees right now. Clear your cookies and it stays the same, which is the point of the exercise.
What your browser tells every site it visits
These details travel with every request, before any script runs. Here we read them through the browser, which gives the same values.
What a script on a page can find out
These need a script to run on the page. Scripts from advertising and analytics companies run on many sites, and some read these details.
Summary of my analysis
When you have gone through the details above, press the button for a plain summary of what this page observed in this browser: what it saw, what is worth knowing and what you could change. It also takes into account the two optional checks below if you have run them.
Summary of what was observed
Compare with another browser or a private window
Open this page in the other browser (or in a private window), read it there, press "Copy this report as text" and paste the text here. The comparison happens in this page; nothing is sent. It shows which details change and which do not: switching browser changes many, while a private window usually changes few, because the hardware and settings are the same.
Are trackers blocked? An optional test
The reading above looks at your browser. This test looks at your protection: it asks for a well-known script from seven advertising and analytics servers, in two different ways, and sees whether anything stops the request. It is the only part of this site that contacts other companies, so it never runs by itself.
What exactly is contacted, and what do they learn?
When you press the button, your browser makes two requests to each of these seven servers (fourteen in all), one as a background request and one as a script preload: pagead2.googlesyndication.com, securepubads.g.doubleclick.net, static.ads-twitter.com, bat.bing.com, www.google-analytics.com, connect.facebook.net and sb.scorecardresearch.com. Each one receives what any request carries: your IP address and your browser's user agent. We send no cookies and no referring page. The scripts are only requested, never run. The result stays in this page: it is not stored, and we never receive it. One extra request goes to this site itself, to check that your connection works.
A request that never leaves your browser (stopped by an extension, a filter on your network or a browser setting) counts as stopped. A request that gets any answer counts as answered; a blocker that replies with a stand-in file also counts as an answer, even though the real server was not contacted.
What does your connection reveal? Another optional check
Whatever your browser says about itself, every site also sees the address your requests come from, and a page can sometimes learn an extra address through a feature called WebRTC. This check shows both. It never runs by itself.
What exactly is contacted, and what do they learn?
When you press the button, your browser makes two kinds of request, both to Cloudflare, a company that runs a large part of the web's infrastructure: one to its public connection page (www.cloudflare.com/cdn-cgi/trace), which answers with the address it sees you coming from, and a WebRTC exchange with its public server (stun.cloudflare.com), which is how a page can learn addresses. Cloudflare receives what any request carries, such as your IP address and your browser's user agent; we send no cookies and no referring page. The answers are shown only to you: they are not stored and we never receive them.
How to read the report
Each line is one detail, in the form a script receives it. Open a line to see what it is and how it can be used. The label on the right says how much that kind of detail usually tells apart in published studies: it is a general guide to the kind of detail, not a measurement of your browser.
What is browser fingerprinting?
A cookie is a label a site puts on your browser to recognise it later. You can see and delete cookies, and blocking tools go after them first. A fingerprint is different: nothing is stored on your computer. A script reads many small details that are already there (your screen, fonts, graphics hardware, language, time zone) and combines them. The combination is often different enough from other people's to recognise the same browser again, on the same site or on another one.
That is why deleting cookies does not help against it, and why it matters to know which details your browser gives away.
Why there is no “unique among X browsers” number here
Other tools tell you how rare your combination is, in “bits of information”. A bit is the smallest unit of information: one yes-or-no answer. Every detail that splits the crowd in two adds about one bit, so around 33 bits are enough to single out one person among all of humanity. To say how many bits your details are worth, a tool must have recorded the details of a very large number of other visitors. This site records nothing about anyone, so it has no such population and will not invent a figure.
Some research projects do collect that kind of data and can give such a comparison. Their sample usually comes from people who chose to run a test, so a figure like that is a guide, not a verdict.
What this page cannot tell you
- Whether anyone is tracking you. A detail being readable does not mean a site reads it, and a unique combination does not mean you are being followed. It shows what is possible.
- Whether every tracker is blocked. The optional test asks seven well-known servers. Your protection may treat others differently, so a clean result is a sample, not a guarantee.
- What your browser would do on other sites. Your extensions and settings can change by site.
What you can do with the result
- Read how to browse with less tracking: it covers blocking trackers, the browsers with built-in protection against fingerprinting, and their limits.
- Try Tracker Watch Lens, which shows which third parties a page contacts and lets you block them.
- Look at the weekly measurement of what news sites contact before you click anything. This page looks at your browser, and that one looks at the sites.
Glossary
- Browser fingerprint
- The combination of small details about your browser and device that a script can read and put together to recognise the same browser again, without storing anything on it.
- Combined code
- A short code computed from those details. Two readings with the same code mean the same details.
- Hash
- A short code made from a longer piece of data, always the same for the same data and very different if the data changes slightly. It is used here to show a drawing or a list without printing all of it.
- User agent
- The line of text in which a browser introduces itself to every site.
- Canvas
- A hidden area of a web page where a script can draw. Reading back the drawing shows how your system renders it.
- WebGL and WebGPU
- Ways for web pages to use your graphics card for 3D drawing. Both tell a page something about your graphics hardware.
- WebRTC
- A browser feature for calls and direct connections between browsers. To make a connection it can reveal network addresses, which is why it matters for privacy.
- STUN server
- A public server that tells a browser which address it appears to have from the outside. WebRTC uses it, and the connection check uses it to see whether an extra address is revealed.
- TLS
- The encryption that protects a web connection. The version shows how modern the connection is.
- Third party
- A company other than the site you are visiting. Advertising and analytics servers are usually third parties.
- VPN
- A service that sends your traffic through another server, so sites see its address instead of yours. It does not change what your browser reveals about itself.