Detecting AI Browsers: A User-Agent Guide

Why User-Agent Detection Matters

As AI browsers like ChatGPT Atlas, Perplexity, and Claude become mainstream, publishers need reliable ways to detect this traffic. User-Agent strings are the primary method.

Understanding User-Agent Strings

Every browser sends a User-Agent string with each HTTP request, identifying itself to the web server:

// Traditional browser (Chrome)
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) 
AppleWebKit/537.36 (KHTML, like Gecko) 
Chrome/120.0.0.0 Safari/537.36

// AI Browser (ChatGPT Atlas)
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) 
AppleWebKit/537.36 (KHTML, like Gecko) 
ChatGPT-Atlas/1.0 Chrome/120.0.0.0 Safari/537.36

AI Browser User-Agent Patterns

1. ChatGPT Atlas

Pattern: ChatGPT-Atlas

ChatGPT-Atlas/1.0

Detection logic:

function isAtlas(userAgent) {
  return /ChatGPT-Atlas/i.test(userAgent);
}

2. Perplexity Browser

Pattern: Perplexity

Perplexity/2.0 Safari/605.1.15

Detection logic:

function isPerplexity(userAgent) {
  return /Perplexity//i.test(userAgent);
}

3. Claude Browser

Pattern: Claude-Browser

Claude-Browser/1.0 AppleWebKit/537.36

4. Google AI (Gemini/Bard)

Pattern: Google-AI or Gemini

Google-AI/1.0 (Gemini)

5. Bing Copilot

Pattern: Copilot

Mozilla/5.0... Copilot/1.0...

Complete Detection Function

Here's a comprehensive function to detect all major AI browsers:

function detectAIBrowser(userAgent) {
  const patterns = {
    atlas: /ChatGPT-Atlas/i,
    perplexity: /Perplexity//i,
    claude: /Claude-Browser/i,
    gemini: /Google-AI|Gemini/i,
    copilot: /Copilot//i,
  };

  for (const [browser, pattern] of Object.entries(patterns)) {
    if (pattern.test(userAgent)) {
      return {
        isAI: true,
        browser: browser,
        confidence: 0.95
      };
    }
  }

  return {
    isAI: false,
    browser: 'unknown',
    confidence: 0
  };
}

Server-Side Detection

Node.js / Express

app.get('/', (req, res) => {
  const userAgent = req.headers['user-agent'];
  const detection = detectAIBrowser(userAgent);
  
  if (detection.isAI && detection.browser === 'atlas') {
    // Serve AI-optimized content
    res.render('ai-optimized', { browser: 'atlas' });
  } else {
    // Serve standard content
    res.render('standard');
  }
});

Cloudflare Workers

export default {
  async fetch(request) {
    const userAgent = request.headers.get('user-agent');
    const isAtlas = /ChatGPT-Atlas/i.test(userAgent);
    
    if (isAtlas) {
      return new Response('Atlas-optimized content', {
        headers: { 'Content-Type': 'text/html' }
      });
    }
    
    return fetch(request);
  }
}

Client-Side Detection

Detect AI browsers in JavaScript:

// In the browser
const userAgent = navigator.userAgent;
const isAtlas = /ChatGPT-Atlas/i.test(userAgent);

if (isAtlas) {
  console.log('Atlas browser detected!');
  // Initialize Atlas-specific features
}

Best Practices

1. Use Regular Expressions

User-Agent strings can vary. Use flexible regex patterns:

// ✅ Good (flexible)
/ChatGPT-Atlas/i

// ❌ Bad (too strict)
userAgent === 'ChatGPT-Atlas/1.0'

2. Cache Detection Results

Don't detect on every request. Cache for the session:

// Store in localStorage
localStorage.setItem('isAtlas', 'true');

// Or session variable (server-side)
req.session.isAtlas = true;

3. Combine with Other Signals

User-Agent alone isn't foolproof. Combine with:

• Referrer headers
• Behavioral analysis
• API headers (when available)

Common Pitfalls

1. Spoofing

User-Agents can be spoofed. Always validate with secondary signals.

2. Version Changes

AI browsers update frequently. Use flexible patterns that don't depend on specific versions.

3. Mobile vs Desktop

AI browsers may have different User-Agents on mobile:

// Desktop
ChatGPT-Atlas/1.0 ... Macintosh

// Mobile (hypothetical)
ChatGPT-Atlas/1.0 ... iPhone

Using Panxo for Detection

Rather than building detection yourself, Panxo handles this automatically:

<script async 
        src="https://cdn.panxo.ai/o/{your-unique-hash}">
</script>

Panxo automatically:

• Detects ChatGPT Atlas and other AI browsers
• Provides confidence scoring
• Updates patterns as browsers evolve
• Handles edge cases and mobile variants