detect()

The headline export. Returns one of the browsers values, narrowed to the Browser union.

Signature	(options?: DetectOptions) => Browser
Returns	'android' | 'chrome' | 'edge' | 'firefox' | 'ie' | 'opera' | 'safari' | 'unknown'
Bundle cost	~1.4 kB (full library, min+gz)
SSR safe	✅ Pass { userAgent } to pin

Signature

function detect(options?: DetectOptions): Browser;

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

type Browser =
  | 'android'
  | 'chrome'
  | 'edge'
  | 'firefox'
  | 'ie'
  | 'opera'
  | 'safari'
  | 'unknown';

Behaviour

Detection runs most-specific first to avoid Chromium-family collisions. Order:

1. Edge (legacy Edge/, Chromium Edg/, mobile EdgA//EdgiOS/)
2. Opera (Presto Opera/, Chromium OPR/, or window.opera/window.opr)
3. IE (MSIE 6–10 or Trident/ 11)
4. Firefox (any platform, including FxiOS/)
5. Chrome (desktop Chrome/, iOS CriOS/, pure Chromium/)
6. Safari (Apple vendor + Safari UA, minus other-browser-on-iOS tokens)
7. Android WebView (last-resort match on Mozilla/5.0 + Android + AppleWebKit minus the above)
8. 'unknown' — bots, new browsers, empty UA

Examples

Default

import { detect } from 'get-browser';

const browser = detect();
// In Chrome 140 on macOS  → 'chrome'
// In Safari 18 on iPhone  → 'safari'
// In Node (no navigator)  → 'unknown'

Exhaustive switch

import { type Browser, detect, browsers } from 'get-browser';

const message = (b: Browser): string => {
  switch (b) {
    case browsers.CHROME:  return 'Chromium-flavored.';
    case browsers.EDGE:    return 'Microsoft Edge.';
    case browsers.FIREFOX: return 'Mozilla Firefox.';
    case browsers.SAFARI:  return 'Apple Safari.';
    case browsers.OPERA:   return 'Opera.';
    case browsers.IE:      return 'Internet Explorer (please upgrade).';
    case browsers.ANDROID: return 'Android WebView.';
    case browsers.UNKNOWN: return 'A bot, perhaps.';
  }
};

message(detect());

The compiler refuses to build if you forget a case.

SSR / explicit UA

import { detect } from 'get-browser';

const edgeChromiumUA =
  'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 ' +
  '(KHTML, like Gecko) Chrome/140.0.0.0 Safari/537.36 Edg/140.0.0.0';

detect({ userAgent: edgeChromiumUA });
// → 'edge'  (Edge wins over Chrome because Edg/ is more specific)

Testing

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

const SAMPLES = [
  ['Mozilla/5.0 ... Chrome/140.0.0.0 ...',  'chrome'],
  ['Mozilla/5.0 ... Firefox/138.0',          'firefox'],
  ['Mozilla/5.0 (iPhone; ...) Safari/604.1', 'safari'],
] as const;

describe('detect', () => {
  it.each(SAMPLES)('reports %s as %s', (ua, expected) => {
    expect(detect({ userAgent: ua, vendor: '' })).toBe(expected);
  });
});

Pure function when given an explicit UA — no DOM mocking required.

Server route

// Next.js Route Handler — Node runtime
import { detect } from 'get-browser';

export async function GET(req: Request) {
  return Response.json({
    browser: detect({ userAgent: req.headers.get('user-agent') ?? '' }),
  });
}

Notes

Treats explicit input as authoritative

When you pass { userAgent }, the library does not read globalThis.navigator — this keeps the function pure with respect to its inputs (no surprise contamination from jsdom or Playwright globals).

No version numbers

This library returns the family name only. Use ua-parser-js if you need versions.

'unknown' is not a bug

Bot UAs, brand-new browsers, and empty strings all resolve to 'unknown' — handle it as a safe fallback rather than an error.

See also

• isChrome(), isSafari(), and friends — boolean variants.
• browsers — the frozen enum of valid return values.
• DetectOptions — the options shape.
• Playground — try detect() against any UA string.