"What Any Website Can See About You: A Look at MySysInfo"
There's a new privacy transparency tool on the web called MySysInfo, and it's worth a visit — if only to remind yourself how much data your browser leaks by default.
The Concept
MySysInfo is dead simple: you load the page, and it shows you exactly what any website can see about you, with no login required. The data comes entirely from what your browser voluntarily exposes via headers, JavaScript APIs, and IP geolocation. Nothing is guessed or inferred from third-party sources.
What It Reveals
The tool surfaces about a dozen data points, each with a brief explanation of how it works and why websites collect it:
- IP address — your device's network identifier, essential for routing
- Location & coordinates — rough geolocation from IP database lookup, not GPS
- Timezone — read directly from your system clock
- Browser name & version — from the User-Agent header
- Operating system — also from User-Agent
- Device type — desktop, tablet, or mobile
- CPU cores — via
navigator.hardwareConcurrency - Screen resolution & viewport size — two different readings
- Pixel ratio — for high-DPI detection
- Language preferences — from Accept-Language header
- Cookie status — whether cookies are enabled
- Do Not Track — the voluntary (and increasingly ignored) signal
Why This Matters
The most striking thing about MySysInfo is that none of this requires special permission. Browsers don't prompt you for any of it. The IP address is a fundamental part of TCP/IP, the User-Agent is sent on every HTTP request, and JavaScript APIs like navigator.hardwareConcurrency are freely accessible to any script on any page.
This isn't malicious — most of this data powers legitimate features like content negotiation, responsive design, and fraud detection. But it's also the foundation of browser fingerprinting, which can identify users across sessions without cookies. When combined, these signals create a surprisingly unique profile.
The Takeaway
Tools like MySysInfo are valuable precisely because they're mundane. They don't show you a conspiracy; they show you the ordinary plumbing of the web. The real privacy conversation isn't about which companies are spying on you — it's about a system designed forty years ago that never considered privacy a design goal. The headers and APIs we use today were built for a web of documents, not a web of surveillance. Understanding that gap is the first step toward closing it.
Comments
Okay this is genuinely useful because my oldest is home for summer break and spends half the day on that school-issued Chromebook and I had no idea how much stuff those websites can pull up without asking. I mean I knew about cookies obviously but CPU cores?? Screen resolution?? It feels like walking into a store and the clerk immediately writing down your shoe size and how many kids you have before you even say hello 😅
I showed my husband the MySysInfo page and he goes 'oh yeah that’s just browser fingerprinting' like everyone’s supposed to know what that means lol. I swear between this and trying to set up parental controls on three different devices I need a degree just to keep my kids safe online.
Great writeup though! Definitely bookmarking this. Now if someone could explain all this to me in the 12 minutes I have between soccer practice and grocery shopping that would be great 🙃
@tameForge88, your instinct about the store clerk is more apt than you realize. In my forty years at the reference desk, I always announced myself before approaching a patron — “Good morning, may I help you find something?” I would never dream of rifling through someone’s bag while they browsed the stacks. Yet that is precisely what every website does to every visitor, silently, without a greeting, and without consent.
The core of the matter is this: a library’s card catalog is public by design, but the librarian does not follow you home and note which books you checked out in 1997. The web’s architecture, as the author notes, was designed for sharing documents among physicists, not for the commercial surveillance apparatus it has become. User-Agent headers and JavaScript APIs are the technological equivalent of a library that stamps your forehead with every title you glance at.
S. R. Ranganathan, the father of library science, laid down five laws of librarianship. The fifth is this: “A library is a growing organism.” The web is a growing organism too, and it has grown in directions its architects never anticipated. Understanding the gap between intention and implementation is the first step toward reform, as the article says. The tools to see what is being collected are valuable. The courage to ask why it is being collected in the first place is more valuable still.
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