What is my operating system?
// My System Information on the Internet
Whether your device is classified as a desktop, tablet, or mobile phone, based on your browser's user agent string.
The underlying software running your device — Windows, macOS, Android, iOS, Linux, etc.
The number of logical processor cores available in your device, as reported by the browser.
A number describing how many physical pixels make up one "logical" pixel — typically 2 on Retina/high-DPI displays.
What is an operating system, and why does your browser report it?
Your operating system is the foundational software layer that manages your device's hardware and runs every application on it. Windows, macOS, Android, iOS, and Linux are the most common. The OS itself never contacts websites directly — your browser does — but it includes the OS name and version in the User-Agent string it sends with every request.
This is done for compatibility. Some web features work differently across operating systems — font rendering, file system access prompts, touch event handling — and developers use the OS information to account for these differences. Analytics teams also track OS distribution to understand what platforms their audience uses.
The OPERATING_SYSTEM value shown above is read directly from the User-Agent string your browser sent when this page loaded. No permission was required, and this same value is available to every website you visit.
What is device type detection used for?
Whether you are on a desktop, tablet, or phone is inferred from signals in your User-Agent string. Websites use this for responsive design — serving a touch-optimized layout to mobile visitors or a full-width experience to desktop users, without requiring you to do anything.
Beyond layout, device type is used to decide which features to enable. Some interactive elements — hover menus, drag interactions, right-click context menus — do not translate well to touchscreens, and developers may disable or replace them when a mobile device is detected.
Advertising platforms also use device type to select the most appropriate ad format — vertical video for mobile feeds, wider banner formats for desktop sidebars. This is one of the more commercially significant uses of device detection.
CPU cores and pixel ratio in practical terms
CPU core count is exposed through navigator.hardwareConcurrency. For most websites — news, shopping, social — this value is never read. Where it matters is in performance-heavy web applications: browser-based video editors, games, or data tools that can split work across multiple threads. Knowing the core count helps them tune parallel processing to what your device can handle.
Pixel ratio has a more direct day-to-day effect. On a Retina or high-DPI display (pixel ratio of 2 or more), standard-resolution images look slightly blurry. Websites that care about visual quality check the pixel ratio and serve higher-resolution versions of images or icons to these screens — while keeping standard-resolution assets for displays that do not need them, saving bandwidth.
How OS and device info contribute to device fingerprinting
Your OS name, device type, CPU core count, and pixel ratio are all individually common values — millions of people share each one. But combined with your browser name and version, language setting, timezone, and screen resolution, the resulting profile becomes statistically uncommon enough to identify you across visits without any cookie.
This is the same fingerprinting concept covered in more depth on our browser page. Screen resolution and viewport size add further signal to this profile — see how on our screen resolution page →
Frequently asked questions
Common questions about operating systems, device detection, and what websites can see.
What is my operating system?
Your operating system (OS) is the foundational software that runs your device — Windows, macOS, Android, iOS, and Linux are the most common. Your browser includes your OS name and version in the User-Agent string it sends with every web request, so any website you visit can read it without asking for permission.
Can a website tell if I'm on a phone or a computer?
Yes. Browsers include signals in the User-Agent string that indicate whether the device is a desktop, tablet, or mobile phone. Websites use this to serve the appropriate layout — a touch-optimized mobile interface or a full desktop experience — and to make decisions about which features to enable.
Why does my CPU core count matter to a website?
For most visitors, it rarely matters. Browsers expose core count through navigator.hardwareConcurrency, which some performance-sensitive web applications use to decide how much parallel work to hand off to your device. Video editors, games, and data processing tools might use it — a typical news site or online store does not.
What is pixel ratio and why does it matter?
Pixel ratio (device pixel ratio) describes how many physical screen pixels correspond to one logical CSS pixel. A ratio of 2 — common on Retina displays and most modern smartphones — means the screen is high-DPI. Websites use it to decide whether to serve higher-resolution images, which look sharper on these screens without wasting bandwidth on standard displays.
Is my OS information used to track me?
Your OS is one of many signals that contribute to browser fingerprinting — where your combination of browser, OS, language, screen size, and other attributes can make you identifiable across visits without cookies. No single value is unique, but the combination often is. This is the same concept described in more depth on our browser page.
Your OS is just one of many signals shared automatically with every site you visit. See everything else this connection reveals →