Introduction

What is ua-browser?

ua-browser is a zero-dependency TypeScript detection library that works in both browser and Node.js environments. It goes beyond parsing UA strings by using hardware signals and Client Hints to stay accurate when the UA string is frozen or spoofed.

Why UA Strings Aren't Enough

UA strings are the traditional way to detect the browser environment, but they break down in several well-known scenarios:

Scenario	The problem
Chrome privacy freeze	Chrome 109+ locks the minor version to 0.0.0 — Chrome/149.0.0.0 is every Chrome 149.x user's UA
macOS 26+ freeze	Apple froze the macOS version in Chrome's UA at Mac OS X 10_15_7 starting from macOS 26
Phone in desktop mode	The UA claims desktop, but the device is still a phone — screen size, touch, and safe-area all say mobile
Headless browser spoofing	Playwright and Puppeteer default UAs are indistinguishable from real Chrome
AI crawlers	GPTBot, ClaudeBot, and similar bots use their own UA format — string matching misses or misidentifies them

ua-browser fills these gaps using hardware signals (WebGL renderer, CSS safe-area, Vibration API, etc.) and Client Hints (Sec-CH-UA-* / getHighEntropyValues).

Choosing the Right API

API	Environment	Capability	Use when
uaBrowser.detect()	Browser (async)	UA + hardware signals + Client Hints	Browser-side default — need accurate version, device, arch
uaBrowser()	Browser (sync)	UA + basic navigator signals	Quick read, version accuracy not required
parseHeaders(headers)	Node.js / SSR	UA + Sec-CH-UA-* request headers	Server-side with Client Hints headers available
parseUA(ua)	Node.js / SSR	UA string only	Server-side with no Client Hints headers

Installation

npm

npm i ua-browser

pnpm

pnpm add ua-browser

yarn

yarn add ua-browser

CDN

<script src="https://cdn.jsdelivr.net/npm/ua-browser/dist/index.min.js"></script>
<script>
  const info = uaBrowser()
  console.log(info.browser) // 'Chrome'
</script>