Websites leak their tech stack in five places: HTML source, HTTP headers, cookies, loaded scripts, and meta tags. If you know where to look, you can identify a site's stack in under a minute. This guide walks through five methods, from zero-effort to programmatic.
Method 1: The free lookup tool (10 seconds)
The fastest way is a hosted detector.
- Paste any domain into Web Radar's homepage. No signup, unlimited lookups.
- You get the full stack: hosting, CDN, CMS, frameworks, analytics, payments, CRM.
Method 2: Browser extension (manual, still free)
Wappalyzer's extension still works, though bulk export has moved behind a paywall. Install, visit a page, click the icon. Good for manual sales research on 5–20 domains a day.
Limitation: you can only inspect what you personally visit. No bulk, no CSV.
Method 3: Developer tools (for engineers)
If you want to verify a detector's output, or learn what signals drive the guess:
curl -I https://example.com
Headers like Server, X-Powered-By, X-Generator, Set-Cookie (look for PHPSESSID, JSESSIONID, _shopify_*), and Link: <*>; rel=preload reveal most of the stack. Then view-source: on the page: meta tags, script src attributes, and CSS classnames fill in the rest.
This is the layer Wappalyzer's rules pattern-match. The detection patterns are open-source: 7,200+ rules, MIT-licensed.
Method 4: API for programmatic detection
When you need to run detection across hundreds of domains programmatically:
Key facts
- Input
- Domain or URL
- Output
- JSON: tech list with versions + categories
- Rate limit
- Tier-based (free/pro/enterprise)
- Auth
- API key in X-API-Key header
Every serious technographics vendor has one. Web Radar's is priced per-call on paid tiers, with a free allowance for evaluation.
Method 5: Buy a pre-filtered dataset
When you don't want to crawl anything at all. You want the list.
Instead of "detect tech on domain X," flip the question: "give me every domain running tech Y, in country Z, with N+ employees." That's what Web Radar's datasets answer. One checkout, one CSV, done.
Which method should you pick?
- One-off research → Free lookup tool.
- Continuous manual checking → Browser extension.
- Programmatic detection across a crawl you already have → API.
- Targeted lead generation → Pre-filtered dataset.
For 90% of B2B teams, it's the last option. Detecting tech stacks yourself is a solved problem. The real work is deciding what to do with the data.
Frequently Asked Questions
Can I detect the tech stack of a website for free?
Yes. Free lookup tools and browser extensions both cover single-domain checks. They break down when you need to check hundreds of sites.
How accurate is tech stack detection?
For popular stacks (WordPress, Shopify, React, Cloudflare, etc.) accuracy is 90%+. For obscure or server-side-only tools, it drops quickly.
Can I detect the backend language of a website?
Sometimes. Signals like Set-Cookie headers, error pages, and framework-specific URLs reveal PHP, Ruby, Node, or .NET. Compiled binaries behind a reverse proxy often hide completely.
Is it legal to detect a website's tech stack?
Yes. The data you're analyzing (HTTP responses, HTML, headers) is publicly served by the site. You're reading what the server chose to send you.
What's the fastest way to get a list of all sites using a specific technology?
Buy a dataset. Crawling 3M domains yourself costs weeks of engineering; a pre-filtered CSV costs $29–$499.
