How to use User Agent Parser
The User-Agent Parser breaks down any browser UA string into its constituent parts: browser name and version, rendering engine, operating system and version, device type and vendor, and CPU architecture. It can also detect and parse your own browser's user-agent automatically. Parsing is done locally in the browser using ua-parser-js — no data leaves your device.
- Click "Use My User-Agent" to auto-populate your browser's current UA string.
- Or paste any user-agent string into the input field manually.
- The parsed result appears immediately, broken into Browser, Engine, OS, Device, and CPU sections.
- Use the information for compatibility testing, bug reports, or analytics debugging.
Your data never leaves your device — 100% private processing.
Anatomy of a user-agent string
A user-agent string is a text header sent by browsers in every HTTP request. It identifies the application, operating system, vendor, and version. Modern UA strings are notoriously complex due to decades of browser compatibility theatre: most browsers claim to be Mozilla/5.0 for historical reasons, then append tokens identifying their actual engine (AppleWebKit, Gecko, Blink). Chrome's UA includes "Safari" to receive Safari-targeted content. Firefox includes "Gecko". A typical Chrome 120 string on Windows looks like: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36 — despite Chrome being a Blink browser, not WebKit.
| Token | Meaning | Example value |
|---|---|---|
| Mozilla/5.0 | Historical compatibility prefix | Always present in modern browsers |
| Windows NT 10.0 | Windows 10 OS identifier | NT 6.1 = Windows 7, NT 10.0 = Win 10/11 |
| Win64; x64 | Architecture — 64-bit Windows | Also: WOW64 (32-bit on 64-bit OS) |
| AppleWebKit/537.36 | Rendering engine version | Chrome and Edge both use this |
| Chrome/120.0.0.0 | Actual browser and version | The meaningful version token |
| Mobile | Mobile device indicator | Present in mobile UAs |
User-Agent Client Hints and privacy
Modern browsers are moving away from the traditional UA string towards User-Agent Client Hints (UA-CH), which allow servers to request only the specific information they need. This addresses privacy concerns: the traditional UA string reveals OS version, exact browser version, and sometimes device model — data that can be used for fingerprinting. Under UA-CH, the default frozen UA string reveals only the major browser version and platform, while additional details are disclosed only on demand via Sec-CH-UA headers. Chrome started freezing UA minor version numbers in 2023. For user-agent parsing in server-side analytics, migrating to UA-CH is recommended for both privacy and accuracy.
Worked examples
Parse a Chrome UA
Inputs: Mozilla/5.0 … Chrome/120.0.0.0 …
Result: Browser Chrome 120 · Engine Blink · OS Windows 10
Detect device type
Inputs: UA string containing "Mobile"
Result: device type: mobile
Why "Safari" appears
Inputs: Chrome UA tokens
Result: historical compatibility — Chrome is Blink, not WebKit
Glossary
- User-Agent
- An HTTP request header identifying the client software, including browser, OS, and device information.
- UA-CH
- User-Agent Client Hints — a modern replacement for the UA string that lets clients disclose only the information a server explicitly requests.
- Rendering engine
- The browser component that parses HTML/CSS and renders the page; Blink (Chrome/Edge), Gecko (Firefox), and WebKit (Safari) are the main ones.
- Fingerprinting
- Identifying a user across sessions by combining browser attributes (UA, screen size, fonts, etc.) into a unique signature without cookies.
- OUI
- Organizationally Unique Identifier — the first three bytes of a MAC address that identify the network hardware manufacturer.
Related reading
Frequently Asked Questions
Why use User Agent Parser?
- Parse any UA string into browser name/version, engine, OS, device type, and CPU architecture
- Auto-detect your own browser's current user-agent with one click for quick environment checks
- Identify mobile, tablet, or desktop device type from a UA string without writing code
- Understand which UA tokens identify the real browser versus historical compatibility prefixes
Common use cases
- Identify the exact browser version in a bug report to reproduce a rendering issue locally
- Decode a UA string from server access logs to distinguish bot traffic from real users
- Verify that a mobile emulator sends the correct device UA string during compatibility testing
- Parse a Googlebot UA string to confirm it is a legitimate crawler and not a spoofed bot
- Check whether a UA string from a headless CI browser matches the expected Chrome version
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