getOS()

The OS counterpart to detect(). Returns one of the oses values, narrowed to the OS union. Reads Sec-CH-UA-Platform when you give it one.

Signature	(options?: DetectOptions) => OS
Returns	'macos' | 'windows' | 'linux' | 'ios' | 'android' | 'chromeos' | 'unknown'
Bundle cost	~250 bytes when tree-shaken on its own
SSR safe	✅ Pass { userAgent } and/or { clientHints: { platform } }

Signature

function getOS(options?: DetectOptions): OS;

interface DetectOptions {
  readonly userAgent?: string;
  readonly vendor?: string;
  readonly clientHints?: ClientHints;
}

interface ClientHints {
  /** Value of `Sec-CH-UA-Platform`. Quoted or unquoted; case-insensitive. */
  readonly platform?: string;
}

type OS =
  | 'android'
  | 'chromeos'
  | 'ios'
  | 'linux'
  | 'macos'
  | 'windows'
  | 'unknown';

Why this exists

The library already had isAndroid() — but that's the Android WebView browser, not the Android OS. The other OSes had no first-class answer at all. getOS() plugs that hole with a single canonical primitive:

import { getOS, oses } from 'get-browser';

const shortcut = getOS() === oses.MACOS ? '⌘ K' : 'Ctrl K';

It pairs naturally with detect():

Question	Answer
Which browser is this?	detect()
Which OS is it running on?	getOS()

Detection order

Most-reliable signal first — most-specific UA token next:

1. Client Hints — options.clientHints.platform (the Sec-CH-UA-Platform request header). Wins if present and recognised.
2. iOS — UA contains iPhone / iPad / iPod.
3. ChromeOS — UA contains CrOS.
4. Android — UA contains Android (checked before Linux, because Android UAs include Linux).
5. Windows — UA contains Windows NT, Win64, Win32, or Windows Phone.
6. macOS — UA contains Mac OS X or Macintosh.
7. Linux — UA contains Linux (covers desktop Linux and ChromeOS-derived browsers that omit the CrOS marker).
8. 'unknown' — bots, brand-new platforms, empty UA.

Examples

⌘ vs Ctrl shortcut

import { getOS, oses } from 'get-browser';

const modifier = getOS() === oses.MACOS ? '⌘' : 'Ctrl';
hint.textContent = `${modifier} K to open the command palette`;

Download button

import { getOS, oses } from 'get-browser';

const downloads = {
  [oses.WINDOWS]: { label: 'Download for Windows', href: '/dl/app.exe' },
  [oses.MACOS]:   { label: 'Download for macOS',   href: '/dl/app.dmg' },
  [oses.LINUX]:   { label: 'Download for Linux',   href: '/dl/app.deb' },
  [oses.IOS]:     { label: 'Open in App Store',    href: 'https://apps.apple.com/…' },
  [oses.ANDROID]: { label: 'Open in Play Store',   href: 'https://play.google.com/…' },
} as const;

const cta = downloads[getOS()] ?? { label: 'Get the app', href: '/install' };

SSR (Edge / Workers)

// Next.js Edge / Cloudflare Worker — prefer the client-hint header.
import { getOS } from 'get-browser';

export function GET(req: Request) {
  const os = getOS({
    userAgent: req.headers.get('user-agent') ?? '',
    clientHints: {
      platform: req.headers.get('sec-ch-ua-platform') ?? undefined,
    },
  });
  return Response.json({ os });
}

Sec-CH-UA-Platform is the only signal that survives Chromium's User-Agent Reduction. If the browser sends it, prefer it.

Unit test

import { describe, expect, it } from 'vitest';
import { getOS, oses } from 'get-browser';

it('routes Mac visitors to the dmg download', () => {
  const ua =
    'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 ' +
    '(KHTML, like Gecko) Chrome/140.0.0.0 Safari/537.36';
  expect(getOS({ userAgent: ua })).toBe(oses.MACOS);
});

The oses enum

export const oses: {
  readonly ANDROID:  'android';
  readonly CHROMEOS: 'chromeos';
  readonly IOS:      'ios';
  readonly LINUX:    'linux';
  readonly MACOS:    'macos';
  readonly WINDOWS:  'windows';
  readonly UNKNOWN:  'unknown';
};

Use it the same way you'd use browsers — getOS() === oses.MACOS beats getOS() === 'macos' because the enum value is the typo-proof canonical reference.

Client Hints (Sec-CH-UA-Platform)

Sec-CH-UA-Platform is a structured-headers string: the raw header value is wrapped in double quotes, e.g. "macOS". getOS() tolerates both quoted and unquoted input and matches case-insensitively:

Header value	Result
"macOS", "Mac OS X", "Darwin"	oses.MACOS
"Windows"	oses.WINDOWS
"Linux"	oses.LINUX
"iOS"	oses.IOS
"Android"	oses.ANDROID
"Chrome OS", "Chromium OS"	oses.CHROMEOS
anything else	UA fallback

The conflict-resolution rule: if a known hint is provided, it wins — even when it contradicts the UA. That's the forward-compatible path Chromium recommends, because the UA string is deliberately losing entropy.

Caveats

iPadOS Safari masquerading as macOS

When "Request Desktop Website" is on (the default in iPadOS 13+), Safari ships a Macintosh UA indistinguishable from a real Mac. Pure UA detection returns 'macos' in that case.

Two workarounds:

// SSR — preferred. Safari sends "iOS" in Sec-CH-UA-Platform.
getOS({
  userAgent: req.headers.get('user-agent') ?? '',
  clientHints: { platform: req.headers.get('sec-ch-ua-platform') ?? undefined },
});

// Client-side — combine with a touch-point check.
import { getOS, oses } from 'get-browser';
const os = getOS();
const isReallyMac = os === oses.MACOS && navigator.maxTouchPoints <= 1;

When you should not reach for getOS()

If you're picking CSS, prefer @media / @supports. If you're feature-detecting, prefer the feature directly. getOS() is for product decisions where the OS itself is the answer — shortcuts, store links, download targets.

See also

• detect() — the browser counterpart.
• isAndroid() — Android browser, not OS. (Use getOS() === oses.ANDROID for the OS.)
• oses — the frozen enum.
• types — OS, ClientHints, DetectOptions.