UserDNAjs

Modern Browser Fingerprinting Library

A lightweight, modular fingerprint generator library for creating unique user identifiers in web applications without compromising user privacy.

• 🐙 GitHub Repository - Open source code
• 📚 Documentation - Get started guide & examples

Features

• 🧬 Simple User Identification: Generate consistent fingerprints for returning visitors
• 🧩 Modular Architecture: Only use the fingerprinting techniques you need
• 🔒 Privacy-Focused: No server-side components or data collection
• ⚙️ Basic Customization: Support for up to 2 custom components
• 📝 TypeScript Support: Full TypeScript definitions included
• 📦 Multiple Formats: Use as an ES module, CommonJS module, or via CDN
• 🪶 Small Footprint: Minimal impact on page load times
• 💾 Easy Storage: Built-in support for localStorage and sessionStorage

Quick Start

import { createUserDNA } from 'userdnajs';

// Create a new instance with default options
const userDNA = createUserDNA();

// Get a visitor ID
userDNA.getVisitorId().then(id => {
  console.log('Visitor ID:', id);
});

// Get the full fingerprint
userDNA.getFingerprint().then(result => {
  console.log('Fingerprint result:', result);
});

Configuration Example

import { createUserDNA } from 'userdnajs';

const userDNA = createUserDNA({
  // What components to include in the fingerprint
  includeBrowserInfo: true,
  includeScreenInfo: true,
  includeTimezone: true,
  includeLanguage: true,
  includeStorage: true,
  
  // Storage configuration
  storagePrefix: 'myapp',
  storageType: 'localStorage', // 'localStorage', 'sessionStorage', or 'none'
  
  // Add custom fingerprinting components (max 2)
  customComponents: [
    {
      name: 'customData',
      getValue: () => 'some-custom-value'
    },
    {
      name: 'timestamp',
      getValue: () => new Date().toISOString()
    }
  ]
});

Why UserDNAjs?

Modern web applications often need to identify returning users without requiring account creation. UserDNAjs provides:

• Easy User Identification: Generate consistent fingerprints to recognize returning visitors
• Lightweight Implementation: Small size with minimal performance impact
• Privacy Respecting: No backend dependencies or data collection
• Flexible Integration: Use only the components you need, with easy configuration

Core API

Available Methods

// Get visitor ID (fingerprint hash)
userDNA.getVisitorId().then(id => {
  console.log('Visitor ID:', id);
});

// Check if current visitor matches previous ID
userDNA.isSameVisitor('previous-id').then(isSame => {
  if (isSame) {
    console.log('Same visitor detected');
  }
});

// Update options after initialization
userDNA.updateOptions({
  includeScreenInfo: false,
  storageType: 'sessionStorage'
});

// Get current options
const options = userDNA.getOptions();

Use Cases

UserDNAjs is designed to provide simple, privacy-focused browser fingerprinting for applications that need to identify users across sessions without requiring authentication.