The 36 techniques running on this site: what each one exposes, the mechanism behind it, and where browser defenses currently stand. Every one is implemented — nothing here is hypothetical.
Written to be read alongside the data page: each entry links to the table it produces.
Nothing on this list requires JavaScript, consent, or any action by the visitor. The browser volunteers it as part of asking for the page.
Browser and platform, preferred languages in ranked order, compression support, and the page you came from.
Every HTTP request carries a header block. The server reads it directly; the page never has to ask for anything.
Unchanged and unchangeable — headers are how the web works. The user-agent string itself has been frozen and reduced in Chrome and Safari to limit what it leaks.
Processor architecture and bitness, exact browser build to the patch number, operating system version, device model, color-scheme preference, viewport size.
The server replies with an Accept-CH header listing what it wants. The browser then attaches those values to every subsequent request. Critical-CH makes it retry the very first request so nothing is missed.
Actively expanding in Chromium. Presented as a privacy improvement over the user-agent string, because the values are requested rather than broadcast — but a site that asks receives more precise data than the old string ever carried.
Which browser engine you really are, regardless of what your user-agent string claims.
Each engine emits its headers in its own fixed sequence. Reading the raw order requires access below the framework layer, which is why this page runs a custom HTTP server.
No mitigation exists or is planned. The same principle applies further down the stack in TLS handshake fingerprinting, which this page does not perform.
Protocol version, source address and port, whether the connection was reused.
Read straight from the TCP socket carrying the request.
Inherent to networking. A VPN or proxy changes the address; it does not remove it.
Color scheme, pixel density, window size, input device, accessibility settings, color gamut, and which rendering engine you use — plus whether JavaScript is disabled.
A stylesheet declares one rule per condition, each loading a different background image. The browser only fetches an image when its rule matches, so the pattern of requests tells the server which conditions were true. A @media (scripting: none) rule fires precisely when scripts are off.
No mitigation. Blocking or disabling JavaScript does not affect it, which makes it the standard counter-example to script blocking as a privacy measure.
These techniques recognize a returning visitor with nothing saved on their machine. They survive clearing cookies, private windows, and in some cases a change of browser.
A stable hash unique to your combination of graphics driver, fonts and rasterizer.
The page draws identical text and shapes off-screen and reads the pixels back. Anti-aliasing and font rasterization differ minutely between machines, and the difference is consistent for any one of them.
Firefox and Tor Browser randomize or prompt; Safari returns a value that changes per session. Chrome does not mitigate by default.
The exact GPU model and driver build — effectively the model of computer and its rough price.
WEBGL_debug_renderer_info returns the unmasked vendor and renderer strings. A rendered scene is also hashed, capturing driver-level differences.
Firefox restricts the unmasked strings. Chrome still returns them to any page with no prompt.
A hash reflecting the floating-point behavior of your audio stack.
An oscillator is rendered through a compressor in an offline audio context — never audible — and the resulting samples are summed.
Randomized in Firefox's resist-fingerprinting mode and in Tor Browser. Otherwise unmitigated.
Which typefaces are installed, and therefore which software you own.
Text is measured in each candidate font against the three generic families. A different width means the font resolved, so it exists.
Safari and Firefox limit the visible set to system fonts. No permission is involved anywhere.
One identifier stable across sessions, combining dozens of individually weak signals.
Each signal splits the population; combined, they usually isolate one browser on one machine. The open-source library used here reports its own confidence.
A commercial industry. The open version is deliberately public so its accuracy can be audited.
The true JavaScript engine, independent of any claimed identity.
Error wording, stack formats and floating-point edge cases differ between V8, SpiderMonkey and JavaScriptCore.
Not mitigable without breaking the language. Used mainly to catch browsers lying about what they are.
Whether values on the main page have been altered by an extension or anti-detect tool.
The same properties are read again inside a Web Worker and compared. Spoofing tools frequently patch one context and forget the other.
A detection technique rather than a collection one — and a demonstration that hiding can make you more conspicuous.
How you type and move a pointer — usable to tell whether the same human is present.
Key hold times, gaps between keystrokes, pointer speed, acceleration and path curvature are collected from ordinary events and compared against a stored profile.
In production use for fraud scoring and continuous authentication. No permission prompt exists for it.
Device class, and whether the machine is throttling, on battery saver or already busy.
A fixed benchmark is run several times; absolute speed and the way it degrades are both characteristic.
Timer precision has been coarsened across browsers to blunt timing attacks, which limits precision but not device classification.
Storage is not one thing. It is a dozen compartments cleared by different controls, and an identifier only has to survive in one of them to be restored into all the others.
That deleting cookies alone does not make you a new person.
The same identifier is written to cookies, localStorage, sessionStorage, IndexedDB, Cache Storage, a service worker cache and window.name. On the next visit whichever copy survived repopulates the rest.
Browsers have unified 'clear site data' controls, which does clear these together. The technique survives partial clears, which is what most people actually perform.
A returning visitor even after cookies and site data are cleared.
The server labels a response with a unique ETag. The browser caches it and returns it in If-None-Match on every revalidation, handing the identifier back without ever storing site data.
Mitigated only by clearing or partitioning the HTTP cache. Browsers now partition the cache per site, which stops cross-site use but not recognition by the same site.
A store that survives ordinary cookie clearing and runs after the tab is closed.
A registered worker keeps its own cache and intercepts network requests for the site.
Cleared with site data; otherwise long-lived by design.
How many tabs of a site you have open, and lets state propagate instantly between them.
BroadcastChannel, SharedWorker, Web Locks and storage events all provide same-origin communication between tabs.
Working as designed; no mitigation applicable.
A single site learning about you is one thing. The commercial system depends on the same party appearing on thousands of sites and joining what it sees on each.
Whether an embedded party can recognize you from elsewhere, and whether your browser stops it.
This page embeds a frame from a genuinely different origin — the same server reached by its other hostname — which then sets and reads its own identifier from inside your visit, exactly as an advertising tag does. No outside company is involved.
Third-party cookies are blocked by default in Safari and Firefox and being phased down in Chrome; remaining storage is partitioned per embedding site. This is the most substantial privacy change of the last decade.
Exactly which fields real tags transmit about a visitor.
The page constructs the genuine request shapes used by Google Analytics 4, the Meta Pixel and an OpenRTB bid request, filled with the values collected from you — and displays them without sending anything.
Ubiquitous. A real-time bidding request is broadcast to hundreds of bidders per ad slot, all of whom receive it whether or not they win.
Which page you were on immediately before this one.
Sent automatically to each site, and to embedded third parties within it.
Default referrer policies now trim the value to an origin in most browsers, and this site sets a strict policy of its own.
Individually mundane, collectively identifying. Each of these splits the population into groups, and it is the combination that isolates a person.
Your approximate region without any location permission, plus your language priorities.
Intl reports the resolved timezone, calendar, numbering system and locale directly.
No permission gate exists. Tor Browser reports UTC to everyone.
Display geometry, density, refresh rate, OS accent color, and whether you use reduced motion, increased contrast or forced colors.
Media queries and resolved CSS system colors, all readable synchronously.
Disclosed by design so pages can adapt. Accessibility settings are effectively health-adjacent data shared with every site, with no way to receive the accommodation while withholding the signal.
Processor core count, memory size, touch capability, battery level.
Plain properties on navigator.
Memory is rounded and capped; battery was removed from Firefox and Safari after it was found being used to correlate visitors across sites.
An estimate of your free disk space.
navigator.storage.estimate() derives its quota from available disk.
Deliberately coarsened, but still a personal and slowly-drifting number.
Which media formats decode in hardware, which is close to a chipset signature, and which content-protection systems the device carries.
canPlayType, MediaSource.isTypeSupported, mediaCapabilities.decodingInfo and Encrypted Media Extensions queries.
Required for media playback to work at all; no mitigation proposed.
How many cameras, microphones and speakers are attached.
enumerateDevices() returns entries with blank labels before permission is granted — but the count is visible immediately.
Labels and stable IDs are correctly gated behind permission. The count is not.
Which capabilities you have already allowed or denied elsewhere on the site.
The Permissions API reports current state without prompting.
Intentional, and useful — it also means a site can tell how cautious a user is before asking for anything.
These require an explicit approval. They are included to show the size of the step between 'no prompt' and 'one prompt' — and how little the prompt usually explains.
Position to within a few meters: a building, not a city.
The operating system combines satellite, nearby wi-fi networks and cell towers.
Properly gated. Once granted, a site may keep asking on every return visit.
Whatever you last copied — frequently a password, address or private message.
navigator.clipboard.readText() after approval.
Gated, but nothing indicates afterwards that a read occurred.
Every installed typeface, straight from the operating system — usually unique to a person.
queryLocalFonts() after approval.
Gated in Chromium; not implemented in Firefox or Safari, which regard it as too revealing.
Every attached display: resolution, arrangement on the desk, manufacturer labels.
getScreenDetails() after the window-management permission.
Gated, and a fair description of a person's workspace.
Whether you are at the keyboard and whether the screen is locked — continuously, in the background.
IdleDetector after approval.
Gated in Chromium; opposed by Mozilla and Apple as surveillance-shaped.
Hardware model names and stable identifiers for every recording device.
Granting access once reveals labels and persistent device IDs, along with full track capabilities.
Gated. The identifiers persist across visits for the same origin.
Accelerometer and gyroscope readings whose calibration noise is unique to the individual handset.
Device orientation and motion events, requiring explicit permission on iOS.
Gated on mobile. The physical-device fingerprint it carries survives every browser reset.
Which desktop applications you have installed.
The browser is asked to open each application's private URL scheme; a hit is inferred from the window losing focus. Kept behind an explicit warning here, because a hit can genuinely launch the application.
Repeatedly tightened after public disclosure. Results are heuristic and vary by browser.
A demonstration of surveillance should not itself be surveillance. These techniques are real, documented, and would have worked here. Each was left out for a stated reason.
Invisible form fields that browsers fill with a name, address or card number are a working exploit for extracting personal data, not a demonstration of one. Nothing is learned by building it that this page does not already show.
Timing and paint-based attacks that recover which sites you have visited are attacks on the browser itself, and current techniques are live vulnerabilities rather than settled behavior.
Embedding a real analytics or advertising tag would transmit each visitor's data to those companies. This page builds the exact payloads and displays them instead, which teaches the same lesson without the collection.
Probing third-party endpoints to determine which services you are signed in to sends requests carrying your cookies to companies you did not choose to contact during this visit.
Turning an address into a city means sending it to a third-party database. Every value on this page is computed locally, and that rule was worth keeping.
FingerprintJS, ua-parser-js and detectIncognito alongside direct platform probes. Every value on the data page is computed and displayed locally; nothing is transmitted, and no part of this site contacts another company.