Erlang
Erlang is a general-purpose, concurrent, functional programming language, and a garbage-collected runtime system.
What detecting Erlang tells you about a site
Erlang is the language behind the BEAM VM, built for massively concurrent, fault-tolerant systems — telecoms, messaging, real-time backends. On the web you detect it from a Cowboy `Server` header or the runtime characteristics of a long-lived, connection-heavy service. Its presence is a strong signal of a system that prioritises uptime and concurrency at scale over front-end concerns; the user-facing layer is usually a separate application entirely.
Erlang in a real-world stack
When you find Erlang, it rarely travels alone. Cowboy as the HTTP server; the OTP supervision ecosystem; often Elixir/Phoenix sharing the same VM in newer stacks.
About
Erlang is a general-purpose, concurrent, functional programming language, and a garbage-collected runtime system.
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`).
How we detect Erlang
Sourcemap Explorer carries 1 fingerprint signal for Erlang, spread across 1 channel — response header. The exact patterns are listed below, and you can replay each one in Chrome DevTools to confirm a match by hand.
Each signal alone is rarely conclusive — Sourcemap Explorer cross-references all of them and weights by confidence. You can reproduce any of these checks yourself in Chrome DevTools.
Server-side fingerprint: the response header reveals the technology behind the page. Visible in DevTools → Network → response headers.
Server: Erlang(?: OTP/([\d.ABR-]+))?
FAQ
How do I check if a website is using Erlang?
Open the page in Chrome, click the Sourcemap Explorer toolbar icon, and read the Stack tab. Erlang's specific fingerprints here are response header, and the popup flags Erlang whenever any combination of them is found. The same checks can be reproduced manually in DevTools — see the "How we detect" section above.
What Erlang version can Sourcemap Explorer detect?
Erlang 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 Erlang?
Official site: https://www.erlang.org. 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 Erlangand you'll see the exact version pulled from the bundled package.json when sourcemaps are exposed.