How to Detect What Technologies a Website Uses

Ever wondered what framework powers a website? Whether you're doing competitive research, evaluating vendors, or just curious, knowing a site's tech stack can be incredibly valuable.

Why Detect Website Technologies?

• Competitive analysis - Understand what tools your competitors use
• Sales intelligence - Know if a prospect uses technologies you integrate with
• Security research - Identify potentially vulnerable software
• Learning - Discover new tools and frameworks

Manual Detection Methods

1. View Source Code

The quickest way to get hints about a site's technology:

<!-- React apps often have a root div -->
<div id="root"></div>

<!-- Next.js adds specific script tags -->
<script src="/_next/static/chunks/main.js"></script>

<!-- WordPress has telltale signs -->
<link rel="stylesheet" href="/wp-content/themes/theme-name/style.css" />

2. Check HTTP Headers

Response headers often reveal server technology:

Server: nginx
X-Powered-By: Express
X-Generator: Drupal 9

3. Inspect Network Requests

The browser's Network tab shows:

• API endpoints (revealing backend frameworks)
• Third-party scripts (analytics, CDNs)
• Asset paths (build tools, bundlers)

Browser Extensions

Wappalyzer

The most popular option. Shows technologies in a convenient popup. Detects:

• JavaScript frameworks
• CMS platforms
• Analytics tools
• E-commerce platforms
• And 1,400+ more technologies

BuiltWith

Focuses on marketing technologies. Great for understanding a site's MarTech stack.

WhatRuns

Similar to Wappalyzer, with a focus on running costs estimation.

Programmatic Detection

For building apps or analyzing multiple sites, you need an API approach.

Using Katsau's Tech Detection API

const response = await fetch(
  'https://api.katsau.com/v1/tech?url=https://example.com',
  {
    headers: { 'Authorization': 'Bearer YOUR_API_KEY' }
  }
);

const { data } = await response.json();

console.log(data.technologies);
// [
//   { name: "React", category: "JavaScript Framework", version: "18.2.0" },
//   { name: "Next.js", category: "Web Framework", version: "14.0" },
//   { name: "Vercel", category: "Hosting" },
//   { name: "Tailwind CSS", category: "CSS Framework" }
// ]

What Gets Detected

A good tech detection API identifies:

Frontend

• JavaScript frameworks (React, Vue, Angular, Svelte)
• CSS frameworks (Tailwind, Bootstrap, Bulma)
• Build tools (Webpack, Vite, Parcel)

Backend

• Web frameworks (Next.js, Nuxt, Django, Rails)
• Server software (Nginx, Apache, Node.js)
• Languages (PHP, Python, Ruby, Go)

Infrastructure

• Hosting providers (Vercel, Netlify, AWS, GCP)
• CDNs (Cloudflare, Fastly, Akamai)
• Databases (visible through headers/scripts)

CMS & E-commerce

• WordPress, Drupal, Ghost
• Shopify, Magento, WooCommerce
• Headless CMS (Contentful, Sanity, Strapi)

Marketing & Analytics

• Google Analytics, Mixpanel, Amplitude
• Tag managers
• A/B testing tools

Building a Tech Lookup Tool

Here's a simple React component that displays a site's tech stack:

function TechStackViewer({ url }: { url: string }) {
  const [technologies, setTechnologies] = useState([]);
  const [loading, setLoading] = useState(true);

  useEffect(() => {
    async function fetchTech() {
      try {
        const res = await fetch(
          `https://api.katsau.com/v1/tech?url=${encodeURIComponent(url)}`,
          {
            headers: { 'Authorization': `Bearer ${API_KEY}` }
          }
        );
        const { data } = await res.json();
        setTechnologies(data.technologies);
      } catch (error) {
        console.error('Failed to detect technologies');
      } finally {
        setLoading(false);
      }
    }

    fetchTech();
  }, [url]);

  if (loading) return <div>Analyzing...</div>;

  return (
    <div>
      <h2>Technologies detected on {url}</h2>
      <ul>
        {technologies.map(tech => (
          <li key={tech.name}>
            <strong>{tech.name}</strong>
            <span>{tech.category}</span>
            {tech.version && <span>v{tech.version}</span>}
          </li>
        ))}
      </ul>
    </div>
  );
}

Use Cases

Sales & Marketing

// Check if a prospect uses your integration targets
const techStack = await getTechStack(prospectUrl);
const usesShopify = techStack.some(t => t.name === 'Shopify');

if (usesShopify) {
  // This is a qualified lead for our Shopify app
  await addToOutreach(prospect);
}

Competitive Analysis

// Analyze competitor tech choices
const competitors = ['competitor1.com', 'competitor2.com', 'competitor3.com'];

for (const url of competitors) {
  const stack = await getTechStack(url);
  console.log(`${url} uses:`, stack.map(t => t.name).join(', '));
}

Portfolio Analysis

// Check all your client sites for outdated tech
const clientSites = await getClientSites();

for (const site of clientSites) {
  const stack = await getTechStack(site.url);
  const outdated = stack.filter(t => isOutdated(t));

  if (outdated.length > 0) {
    await notifyClient(site, outdated);
  }
}

Accuracy Considerations

Tech detection isn't perfect. Keep in mind:

1. Minification hides clues - Bundled code is harder to identify
2. Custom builds - Heavily modified frameworks may go undetected
3. Server-side only - Some technologies leave no client-side traces
4. Version detection - Not always possible or accurate

Conclusion

Whether you use browser extensions for quick checks or APIs for automation, technology detection is a valuable tool for developers, marketers, and security researchers.

For programmatic access to tech stack data, an API provides the scalability and reliability you need for production applications.

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Want to detect technologies programmatically? Try Katsau's Tech Detection API - included in all plans.