FingerprintJS is an open-source, client-side browser fingerprinting library that queries browser attributes and computes a hashed visitor identifier from them, aimed at web developers and engineering teams that need to recognise returning browsers without depending on cookies or local storage.

What it is

FingerprintJS runs entirely in the browser. It queries a set of browser attributes, hashes the resulting combination, and returns a stable visitor identifier through a small JavaScript API. The project is written in TypeScript, distributed under the MIT licence, and published both as the npm package @fingerprintjs/fingerprintjs and as a CDN build at https://openfpcdn.io/fingerprintjs/v5. It sits in the JavaScript browser ecosystem and is catalogued under Productivity & Utilities / Browsers & Extensions.

The problem it solves is identifier loss. Cookies and local storage are cleared by users, by browser privacy settings, and by incognito or private mode, so anything stored there disappears exactly when a visitor returns. A fingerprint stays the same in incognito and private mode and even when browser data is purged, which makes it a replacement for cookie-based and local-storage-based visitor tracking in contexts where a persistent identifier matters. The GitHub repository carries 28,466 stars, 2,621 forks and 19 open issues, with the last push dated 2026-09-11.

Key capabilities

• FingerprintJS.load() initialises the agent at application startup, and fp.get() returns a result whose result.visitorId field holds the hashed visitor identifier.
• Identifiers survive incognito or private mode and survive purging of browser data, unlike cookies and local storage.
• Distributed as the npm package @fingerprintjs/fingerprintjs and as a versioned CDN import from https://openfpcdn.io/fingerprintjs/v5.
• Collects browser and audio fingerprint signals, reflected in the repository topics audio-fingerprinting, browser-fingerprint and browser-fingerprinting.
• Ships documentation files for the API, licensing terms and a comparison against the commercial product at docs/api.md, docs/licensing.md and docs/comparison.md.
• Provides a React sample on StackBlitz and a CDN sample, alongside a live demo at https://fingerprintjs.github.io/fingerprintjs.
• Covers fraud-adjacent use cases per its topics, including fraud, fraud-detection, detection and identification.

Who uses it and how

• Teams building fraud detection or duplicate-account checks that need a visitor identifier which survives cookie clearing and private browsing sessions.
• Analytics and product engineering groups that want client-side identification without operating a server-side collection pipeline.
• Developers evaluating device intelligence before committing to the commercial tier, since the same API shape appears in the upgraded product.
• Anyone who wants to see the behaviour first-hand can load the demo, note the identifier, then reopen the page in private or incognito mode and observe that it is unchanged.
• Projects already shipping JavaScript bundles, which can add the library through npm or a single CDN import without a backend component.

Getting started

Install with npm install @fingerprintjs/fingerprintjs and call FingerprintJS.load() followed by fp.get(), or load the agent from the CDN URL https://openfpcdn.io/fingerprintjs/v5 if npm is not available. The README warns that the CDN import fails for users of ad blockers, Brave or Firefox, and directs those cases to the npm package instead.

How it compares

The README positions FingerprintJS directly against Fingerprint Identification, a closed-source commercial device intelligence platform from the same vendor. FingerprintJS generates and processes fingerprints in the browser under the MIT licence at no cost, whereas Fingerprint Identification processes over 100 browser and device signals server-side alongside network-level data, validates that signals have not been tampered with or replayed, and adds Smart Signals for bot detection, VPN detection and browser tampering detection behind a paid platform with a 14-day free trial. The trade is therefore licence and cost against accuracy: the open version can be self-hosted and embedded freely, while the commercial version keeps data handling and signal analysis on the vendor side.

When to use it — and when not to

FingerprintJS has no server component, so there is no database, storage service or SMTP configuration to operate — the whole integration is a client-side script. It should not be chosen when production-grade accuracy or anti-spoofing is the requirement, because the README states plainly that browser-side generation lowers accuracy significantly compared with the commercial version and that client-side fingerprints are vulnerable to spoofing and reverse engineering. Teams that need tamper-resistant identifiers, server-side signal validation or bot and VPN detection should treat this library as an evaluation step rather than a final deployment.

npm install @fingerprintjs/fingerprintjs

import FingerprintJS from '@fingerprintjs/fingerprintjs'

// Initialize the agent at application startup.
const fpPromise = FingerprintJS.load();

(async () => {
  // Get the visitor identifier when you need it.
  const fp = await fpPromise
  const result = await fp.get()
  console.log(result.visitorId)
})()

<script>
  // Initialize the agent at application startup.
  // If you're using an ad blocker or Brave/Firefox, this import will not work.
  // Please use the npm package instead: https://t.ly/ORyXk
  const fpPromise = import('https://openfpcdn.io/fingerprintjs/v5')
    .then(FingerprintJS => FingerprintJS.load());

  (async () => {
    // Get the visitor identifier when you need it.
    const fp = await fpPromise
    const result = await fp.get()
    console.log(result.visitorId)
  })()
</script>