---
title: "TraceTail — Browser fingerprinting API with 99.6% accuracy"
description: "Identify returning visitors without cookies. TraceTail turns 40+ browser signals into a stable visitor ID, the same in normal and incognito windows. 1,000 requests free every month."
url: https://tracetail.io/
updated: 2026-10-05
---

99.6% accuracy

# Browser fingerprinting that just works

Recognize returning visitors without cookies or local storage. TraceTail turns 40+ browser signals into a stable visitor ID that stays the same in normal and incognito windows.

[Get started free](https://tracetail.io/auth)

[See the live demo](https://tracetail.io/live-demo)

- 1,000 requests free every month
- No credit card required
- SDK under 10 KB gzipped

## Your browser's visitor ID

This is the ID TraceTail computes for the browser you're using right now, and every signal behind it.

## Live in three steps

1. ### Create a free account

   Sign in with your email address. No card needed.

2. ### Register your domain

   Get an API key that only works on the domains you list.

3. ### Add the snippet

   Send the visitorId to your backend with the request you want to recognize.

[Read the quick start](https://tracetail.io/docs#quickstart)

**Script tag**

**Before \</body>**

```html
<script src="https://tracetail.io/sdk.js" data-api-key="YOUR_API_KEY"></script>
<script>
  TraceTail.generateFingerprint().then(({ visitorId }) => {
    // Send visitorId to your backend with the request you want to recognize.
  });
</script>
```

**npm**

**npm install @tracetail/js**

```javascript
import { TraceTail } from '@tracetail/js';

const tracetail = new TraceTail({ apiKey: 'YOUR_API_KEY', endpoint: 'https://tracetail.io/api' });
const { visitorId } = await tracetail.generateFingerprint();
```

## Everything you need to recognize a device

One visitor ID per browser, computed in milliseconds, with the controls a production site needs.

### No cookies, no storage

The ID is computed from the browser itself, so clearing cookies changes nothing, and normal and incognito windows get the same ID.

### 40+ browser signals

Canvas and WebGL rendering, 24 font checks, screen, time zone, language and hardware traits, hashed into one visitor ID.

### Flags automated browsers

With an API key, each identification includes an isBot flag for automated browsers such as headless Chrome and WebDriver.

### Domain-locked API keys

Keys only work on the domains you register for them, so they are safe to ship in your page HTML.

### Under 10 KB gzipped

One small script tag or npm package. Works with React, Vue, Angular or plain JavaScript.

### On Cloudflare's network

The API runs on Cloudflare Workers, close to your visitors. Your dashboard shows requests and visitors for every key.

Use cases

## What teams use a visitor ID for

### Account security

Spot a sign-in from a device the account has never used and ask for a second factor only then.

### Signup and promo abuse

See when one device opens account after account to collect the same welcome offer.

### Bots and scrapers

Rate-limit by visitor ID instead of IP address, and treat automated browsers differently.

### Checkout fraud

Notice one device trying card after card, even when it rotates email addresses and IPs.

## Pay only for what you use

1,000 requests free every month, then $0.10 per 1,000. The same rate at every volume.

- 10,000 requests a month

  $0.90

- 100,000 requests a month

  $9.90

- 1,000,000 requests a month

  $99.90

[See pricing details](https://tracetail.io/pricing)

## Questions

- What is TraceTail?

  TraceTail is a browser fingerprinting API. Its JavaScript SDK turns 40+ browser signals into a stable visitor ID, so your site recognizes a returning browser without cookies, for example to stop free-trial abuse, link duplicate accounts or flag a sign-in from a new device.

- How accurate is TraceTail?

  TraceTail identifies returning browsers with 99.6% accuracy, and the visitor ID stays the same in normal and incognito windows.

- Does TraceTail use cookies?

  No. The visitor ID is computed from the browser's own traits every time, so nothing is stored in the browser and clearing cookies or site data does not change it.

- Is TraceTail free?

  Every account gets 1,000 identification requests free each month, with no credit card. After that it costs $0.10 per 1,000 requests at every volume. Running the SDK without an API key is free.

- Can I try it without signing up?

  Yes. Add \<script src="https\://tracetail.io/sdk.js">\</script> to any page and call TraceTail.generateFingerprint(): without an API key the SDK computes the visitor ID in the browser and sends nothing.

- Which frameworks does TraceTail work with?

  Any site that runs in a browser: a script tag for plain HTML, and the @tracetail/js npm package for React, Next.js, Vue, Nuxt, Angular, Svelte and other bundled apps.

- Do ad blockers stop TraceTail?

  Blockers that stop fingerprinting services by their domain can block tracetail.io. Serve the SDK and the API from a path on your own site instead (one click if the site is on Cloudflare, or a small proxy on any other host) and the browser only ever talks to your domain.

- Can my server check a visitor ID?

  Yes. The browser can send any value, so TraceTail's Server API lets your backend look up the identification behind a visitor ID with a secret server key before trusting it for a sign-up, login or payment.

- How is TraceTail different from FingerprintJS?

  FingerprintJS is an open-source library that computes a hash in the browser and has no server behind it. TraceTail also registers each identification, checks it for automation and lets your server verify it. Fingerprint, the company behind FingerprintJS, sells a hosted service that costs considerably more at the same volume.

- Can an AI coding agent add TraceTail?

  Yes. Point Claude Code, Codex, Cursor or another agent at https\://tracetail.io/llms.txt, connect the TraceTail MCP server at https\://tracetail.io/mcp, or install the TraceTail skill with npx skills add https\://tracetail.io.

## Start identifying visitors today

1,000 requests free every month, no credit card required. Add a card only when you need more.

[Get started free](https://tracetail.io/auth)

[Read the docs](https://tracetail.io/docs)