Reverse Engineering Like a Pro: How to Inspect Any Website’s Tech Stack

All Notes

Technology

Computer code on a screen.

Curious About the Stack?

Ever landed on a site and wondered, “How did they make this so fast?” or “Is this React or Vue?” Reverse engineering a website’s tech stack is more than just curiosity—it’s a critical skill for competitive research, security auditing, and learning the architecture of industry leaders.

You don’t need to be a hacker to find out. Here’s the professional toolkit for deconstructing any modern web application.

1. The “Network Tab” Forensic Audit

While many developers go straight to the HTML, the Network Tab (F12 > Network) is where the real secrets are hidden.

HTTP Response Headers: Click on the main document request. Look for the Server or X-Powered-By headers. While security-conscious sites hide these, many still leak information (e.g., Server: gws means Google Web Server; via: 1.1 varnish means they use Varnish for caching).
XHR/Fetch Requests: Look at the API calls. Is the endpoint /graphql? If so, they are using GraphQL (likely Apollo or Relay). Does the data come back in a specific JSON format? You can often identify the backend framework by the specific error messages or field names returned.
Asset Paths: Search for URLs like /_next/static/ (pointing to Next.js) or static/js/main.[hash].chunk.js (pointing to a standard Create React App build).

2. CSS Fingerprinting

CSS leaves behind distinct “genetic markers.” By looking at the class names in the DOM, you can identify the styling engine instantly:

Style Marker	Technology Identified
`class="mt-4 p-2 flex..."`	Tailwind CSS
`class="v-application v-main..."`	Vuetify (Vue.js)
`class="css-1a2b3c..."`	Emotion / Styled Components
`class="col-md-6 btn-primary..."`	Bootstrap

3. The Source Map Treasure Hunt

In a production environment, code is usually “minified”—turned into unreadable gibberish to save space. However, many developers accidentally (or intentionally) leave Source Maps enabled.

If you can find a .map file (e.g., main.js.map), you can use the Chrome DevTools to see the original, un-minified source code, complete with folder structures and comments. This is the “Holy Grail” of reverse engineering.

4. Modern Detection Toolkit

If you want to speed up the process, these tools are the industry standard:

Wappalyzer: The most comprehensive browser extension. It identifies everything from the CDN (Cloudflare, Akamai) to the font engine (Google Fonts, Typekit).
BuiltWith: Best for deep-diving into the business side. It shows historical data, like when they switched from AWS to Vercel.
Brave/Chrome Memory Profiler: Not strictly for stack detection, but it tells you exactly how many gigabytes of RAM that “simple” React app is eating, giving you a hint about its state-management complexity (Redux, MobX).

5. The CLI Route (Automation)

For the terminal power user, curl and whatweb are the way to go:

# Get quick headers
curl -I https://github.com

# Use WhatWeb for a deep fingerprint
whatweb https://github.com

Conclusion

Reverse engineering isn’t just about “snooping.” It’s about architectural literacy. By analyzing how sites like Airbnb, GitHub, or Netflix handle their routing, asset loading, and state, you can learn more in afternoon of “Inspect Element” than in a week of tutorials.