Website Technology Checker API: Detect Any Site's Tech Stack Programmatically

Need to know what technologies a website is running? A technology checker API lets you answer that question with a single HTTP request. Send a URL, get back a structured list of every framework, CMS, CDN, analytics tool, and server the site uses.

This guide covers what a tech stack detection API is, how it works under the hood, and how to make your first API call with code examples in curl, Python, and JavaScript. We'll also compare the three main options—BuiltWith, Wappalyzer, and DetectZeStack—so you can pick the right one for your budget and use case.

What Is a Tech Stack Detection API?

A tech stack detection API is a web service that takes a URL as input and returns a structured list of technologies that website uses. Instead of manually inspecting page source, checking HTTP headers, and running DNS lookups, you let the API do it all in one request.

Common use cases:

• Sales intelligence: Enrich leads with technology data. Know which prospects run Shopify, Salesforce, or HubSpot before you reach out. See our guide on building a lead enrichment pipeline.
• Competitive analysis: Track what technologies your competitors use and when they switch. Monitor their CDN, analytics, and A/B testing tools.
• Security auditing: Identify outdated frameworks and libraries with known vulnerabilities. Map detected technologies to the NVD using CPE identifiers.
• Market research: Measure technology adoption across thousands of websites. Build datasets on CMS market share, framework popularity, or CDN usage.
• Developer tooling: Integrate tech detection into CI/CD pipelines, monitoring dashboards, or internal tools.

How Technology Detection Works

Tech detection APIs use multiple analysis layers. Each layer reveals different technologies that the others might miss.

1. HTTP Header Fingerprinting

The first thing any tech detection tool checks is the HTTP response headers. Many web servers, frameworks, and platforms advertise themselves here:

• Server: nginx/1.25.3 — identifies the web server and version
• X-Powered-By: Express — reveals the backend framework
• X-Drupal-Cache — indicates Drupal CMS
• CF-Ray — confirms Cloudflare CDN

Header analysis is fast but limited. Many production sites strip these headers for security. That's why good APIs use additional detection layers.

2. HTML and DOM Pattern Matching

The API fetches the page's HTML and scans for known patterns:

• Meta tags: <meta name="generator" content="WordPress 6.4">
• Script sources: URLs containing jquery.min.js, react.production.min.js, gtag/js
• CSS classes: Bootstrap's col-md-, Tailwind's flex utility classes
• HTML comments: Some CMS platforms leave signature comments in the source
• Cookie names: __cf_bm (Cloudflare), _shopify_s (Shopify)

This is the core of most detection engines. The open-source wappalyzergo library (which DetectZeStack uses) maintains over 7,200 technology fingerprints using this approach.

3. DNS CNAME Analysis

DNS records reveal infrastructure that's invisible in HTTP responses. When a site points its domain to a CDN or hosting provider via CNAME, a DNS lookup exposes the provider:

• example.com CNAME d1234.cloudfront.net → Amazon CloudFront
• www.example.com CNAME example.com.cdn.cloudflare.net → Cloudflare
• example.com CNAME shops.myshopify.com → Shopify

Most tech detection tools skip DNS entirely. DetectZeStack checks CNAME records against 111 CDN and hosting provider signatures.

4. TLS Certificate Inspection

The TLS certificate used for HTTPS reveals the certificate authority, which often correlates with specific infrastructure:

• Let's Encrypt — common with self-hosted setups, Caddy, Traefik
• Cloudflare Inc — confirms Cloudflare proxy
• Amazon — AWS Certificate Manager, likely behind CloudFront or ALB
• DigiCert — often enterprise or financial sites

Combined, these four layers catch technologies that any single method would miss. A site might strip all HTTP headers but still expose its CDN through DNS and its certificate authority through TLS.

Making Your First API Call

Let's walk through calling a tech detection API. We'll use DetectZeStack via RapidAPI, which has a free tier (100 requests/month, no credit card).

Step 1: Get an API Key

1. Go to DetectZeStack on RapidAPI
2. Click "Subscribe to Test" and select the free Basic plan
3. Copy your X-RapidAPI-Key from the code snippets panel

Step 2: Make a Request

curl:

curl -s "https://detectzestack.p.rapidapi.com/analyze?url=stripe.com" \
  -H "X-RapidAPI-Key: YOUR_API_KEY" \
  -H "X-RapidAPI-Host: detectzestack.p.rapidapi.com" | python3 -m json.tool

Python:

import requests

url = "https://detectzestack.p.rapidapi.com/analyze"
params = {"url": "stripe.com"}
headers = {
    "X-RapidAPI-Key": "YOUR_API_KEY",
    "X-RapidAPI-Host": "detectzestack.p.rapidapi.com"
}

response = requests.get(url, headers=headers, params=params)
data = response.json()

for tech in data["technologies"]:
    print(f"{tech['name']} ({tech['category']})")
    if tech.get("version"):
        print(f"  Version: {tech['version']}")
    if tech.get("cpe"):
        print(f"  CPE: {tech['cpe']}")

JavaScript (Node.js):

const response = await fetch(
  "https://detectzestack.p.rapidapi.com/analyze?url=stripe.com",
  {
    headers: {
      "X-RapidAPI-Key": "YOUR_API_KEY",
      "X-RapidAPI-Host": "detectzestack.p.rapidapi.com",
    },
  }
);

const data = await response.json();

data.technologies.forEach((tech) => {
  console.log(`${tech.name} (${tech.category})`);
  if (tech.version) console.log(`  Version: ${tech.version}`);
  if (tech.cpe) console.log(`  CPE: ${tech.cpe}`);
});

API Response Walkthrough

Here's an annotated example of what comes back when you analyze stripe.com:

{
  "url": "https://stripe.com",
  "domain": "stripe.com",
  "status_code": 200,
  "technologies": [
    {
      "name": "Cloudflare",         // CDN / security provider
      "category": "CDN",
      "source": "dns"               // detected via DNS CNAME
    },
    {
      "name": "React",              // Frontend framework
      "category": "JavaScript frameworks",
      "source": "wappalyzer"        // detected via HTML/JS patterns
    },
    {
      "name": "Nginx",              // Web server
      "category": "Web servers",
      "version": "1.25.3",          // version extracted from headers
      "cpe": "cpe:2.3:a:f5:nginx:1.25.3:*:*:*:*:*:*:*",
      "source": "wappalyzer"
    },
    {
      "name": "Google Analytics",   // Analytics
      "category": "Analytics",
      "source": "wappalyzer"
    },
    {
      "name": "Let's Encrypt",      // Certificate authority
      "category": "SSL/TLS certificate authorities",
      "source": "tls"               // detected via TLS inspection
    }
  ],
  "detection_time_ms": 847,
  "cached": false                    // fresh analysis (not from cache)
}

Key things to notice:

• Each technology has a source field telling you how it was detected (wappalyzer, dns, tls, or headers)
• When available, version and cpe fields are included for security workflows
• cached: false means this was a fresh analysis; subsequent requests within 24 hours return cached results
• detection_time_ms shows how long the analysis took

Comparison: BuiltWith vs Wappalyzer vs DetectZeStack

Three main APIs compete in this space. Here's how they compare on the factors that matter most to developers:

When to Choose Each

BuiltWith ($995/mo): Best for enterprise sales teams that need historical technology data, lead lists filtered by tech stack, and market share reports. The largest signature database, but data is crawl-based (not real-time) and the price is prohibitive for individual developers.

Wappalyzer ($450/mo): Good for teams that need CRM integrations (HubSpot, Salesforce, Pipedrive) and real-time detection. The browser extension is free and useful for manual lookups. But API access requires the $450/month Team plan, and it only detects technologies visible in HTTP responses.

DetectZeStack (Free / $9/mo): Built for developers who need an affordable API. Adds DNS and TLS detection layers that competitors lack. Includes CPE identifiers for security workflows. No lead lists or CRM integrations—it's a developer API, not a sales platform.

Beyond Single-URL Analysis

Once you're comfortable with single URL analysis, there are more powerful features to explore:

Batch Analysis

Analyze up to 10 URLs in a single request:

curl -s "https://detectzestack.p.rapidapi.com/batch" \
  -X POST \
  -H "X-RapidAPI-Key: YOUR_API_KEY" \
  -H "X-RapidAPI-Host: detectzestack.p.rapidapi.com" \
  -H "Content-Type: application/json" \
  -d '{"urls": ["stripe.com", "shopify.com", "github.com"]}'

Stack Comparison

Compare two websites and see shared vs. unique technologies:

curl -s "https://detectzestack.p.rapidapi.com/compare?url1=stripe.com&url2=shopify.com" \
  -H "X-RapidAPI-Key: YOUR_API_KEY" \
  -H "X-RapidAPI-Host: detectzestack.p.rapidapi.com"

The response groups technologies into shared, unique_to_url1, and unique_to_url2—useful for competitive analysis.

Webhook Monitoring

Get notified whenever a domain is analyzed by registering a webhook URL. Useful for building monitoring dashboards or triggering alerts when a competitor changes their tech stack.

Getting Started

Getting your first tech detection result takes less than two minutes:

1. Sign up on RapidAPI (free, no credit card)
2. Subscribe to the Basic plan (100 requests/month, free)
3. Copy your API key from the code snippets panel
4. Make a request using any of the code examples above

For full API documentation including all endpoints, parameters, and response schemas, see the OpenAPI spec. Or try the live demo on our homepage—it calls the same API.

Frequently Asked Questions

Related Articles

• Detect Any Website's Tech Stack With a Single API Call — Deep dive into how DetectZeStack works
• BuiltWith vs Wappalyzer vs DetectZeStack — Full three-way comparison
• BuiltWith vs Wappalyzer — Head-to-head feature comparison
• Build a Lead Enrichment Pipeline — Use tech detection for sales intelligence
• Detect Vulnerable Technologies with CPE — Security auditing with CPE identifiers
• BuiltWith Alternative · Wappalyzer Alternative · WhatRuns Alternative