What detecting Haskell tells you about a site
Haskell on a production website is rare and therefore a strong signal in itself: a team that values a pure, strongly-typed functional language enough to run it in production. You detect it from `Server` headers naming Warp (the standard Haskell web server) or framework signatures like Yesod or Servant. Finding it usually points to a domain where correctness guarantees matter a great deal — fintech, compilers, formal-verification-adjacent products — or a deliberately engineering-led team.
The detail that matters for Haskell
Haskell rarely advertises itself. Warp, the standard server, sends a `Server: Warp/<version>` header by default, which is the most reliable tell — but many deployments sit behind nginx or Cloudflare that overwrite it. Because production Haskell is so rare, a Warp header is high-confidence when present, while its absence proves nothing; detection is often by elimination.
Haskell in a real-world stack
When you find Haskell, it rarely travels alone. Warp as the server; Servant or Yesod as the web framework; a typically bespoke, API-first architecture.
About
Haskell is a programming languages catalogued in the Wappalyzer database. Sourcemap Explorer flags it on any page that exposes one of its known signals.
Categories: Programming languages
Quick facts
Detection methodology for Programming languages
Programming languages reveal themselves through extension fingerprints (`.php` URLs for PHP, `.aspx` for ASP.NET), framework-specific patterns and (for client-side runtime languages like TypeScript and Sass) the `node_modules/<lang>/package.json` entry inside the sourcemap. Bun, Node.js and Deno on the server side identify themselves via response headers when emitted (`X-Powered-By: Bun`, `X-Bun-Version`).
FAQ
How do I check if a website is using Haskell?
Open the page in Chrome, click the Sourcemap Explorer toolbar icon, and read the Stack tab. Haskell's fingerprints span response headers, asset URL prefixes, runtime globals and sourcemap paths, and the popup flags Haskell whenever any combination of them is found. The same checks can be reproduced manually in DevTools — see the "How we detect" section above.
What Haskell version can Sourcemap Explorer detect?
Haskell ships as a hosted programming languages rather than a bundled npm package, so version-specific detection isn't always possible. Where the platform leaks a version in response headers (`X-Powered-By`, `Server`, generator meta tags) we surface it; otherwise we report presence only.
Where can I read more about Haskell?
Official site: https://wiki.haskell.org/Haskell. For Sourcemap Explorer's detection guide, see the deep-dive link below or the related guides in the cross-link section.
Keep reading on Sourcemap Explorer
Practical guides
Alternative tools
Detected by Sourcemap Explorer
Open the popup on any page running Haskelland you'll see the exact version pulled from the bundled package.json when sourcemaps are exposed.