Node.js / SSR

UA-only parsing: parseUA()

A pure function with no browser API dependencies — runs in Node.js, Deno, and Edge Runtime:

import { parseUA } from 'ua-browser'

const ua = req.headers['user-agent'] ?? ''
const { browser, os, device, isBot, botName } = parseUA(ua)

if (isBot) {
  res.status(403).end()
  return
}

Limitation: UA string freezing affects server-side detection too — Chrome version is fixed at 149.0.0.0, macOS 26+ shows as 10.15.7. Use parseHeaders() for real values.

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Accurate detection with Client Hints: parseHeaders()

Chrome / Edge 90+ sends Sec-CH-UA-* headers on HTTPS requests. Set the Accept-CH response header once, then use parseHeaders() on subsequent requests:

import { parseHeaders, ACCEPT_CH } from 'ua-browser'

// First response: tell the browser to start sending Client Hints
res.setHeader('Accept-CH', ACCEPT_CH)

// Subsequent requests carry Sec-CH-UA-* headers
const result = parseHeaders(req.headers)

console.log(result.version)   // '149.0.7827.102' — from Sec-CH-UA-Full-Version-List
console.log(result.arch)      // 'x86_64' — from Sec-CH-UA-Arch
console.log(result.osVersion) // '26.5.1' — from Sec-CH-UA-Platform-Version

What parseHeaders() adds over parseUA():

Capability	parseUA()	parseHeaders()
Real browser full version	Frozen UA value	✅ Sec-CH-UA-Full-Version-List
macOS 26+ real version	Frozen UA value	✅ Sec-CH-UA-Platform-Version
CPU architecture	UA inference	✅ Sec-CH-UA-Arch
Brave browser detection	❌	✅ Sec-CH-UA brand
Windows 10 / 11 distinction	❌	✅ Sec-CH-UA-Platform-Version

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Next.js example

// pages/api/detect.ts
import type { NextApiRequest, NextApiResponse } from 'next'
import { parseHeaders, ACCEPT_CH } from 'ua-browser'

export default function handler(req: NextApiRequest, res: NextApiResponse) {
  res.setHeader('Accept-CH', ACCEPT_CH)
  const result = parseHeaders(req.headers as Record<string, string>)
  res.json(result)
}

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Accurate Windows 10 / 11 Detection

Windows 10 and 11 share the same UA string — use Client Hints to tell them apart:

import { parseUA, getWindowsVersion, getNavContext } from 'ua-browser'

// Browser-side only
const nav = getNavContext()
const windowsVersion = await getWindowsVersion(nav)
const { os, osVersion } = parseUA(navigator.userAgent, { nav, windowsVersion })

console.log(osVersion) // '11' or '10'

In SSR, Windows 10/11 distinction is handled automatically by parseHeaders() via Sec-CH-UA-Platform-Version.