Ruby
Ruby is an open-source object-oriented programming language.
What detecting Ruby tells you about a site
Ruby on the web means Ruby on Rails the overwhelming majority of the time. The signals are server-side: a `_session_id` cookie, an `X-Runtime` header (a Rails signature), CSRF meta tags in the HTML, or the Sprockets asset-fingerprint pattern (`application-<hash>.js`). Detecting it tells you the product follows Rails' convention-over-configuration philosophy — a monolithic, server-rendered app with a strong opinionated structure, often a startup that prized shipping speed.
Ruby in a real-world stack
When you find Ruby, it rarely travels alone. Rails with Hotwire/Turbo or a Stimulus sprinkle for interactivity; Puma as the app server; PostgreSQL as the default database.
About
Ruby is an open-source object-oriented programming language.
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 Ruby
Sourcemap Explorer carries 1 fingerprint signal for Ruby, 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: (?:Mongrel|Ruby(?:/([\d\.]+))?)
FAQ
How do I check if a website is using Ruby?
Open the page in Chrome, click the Sourcemap Explorer toolbar icon, and read the Stack tab. Ruby's specific fingerprints here are response header, and the popup flags Ruby whenever any combination of them is found. The same checks can be reproduced manually in DevTools — see the "How we detect" section above.
What Ruby version can Sourcemap Explorer detect?
Ruby 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 Ruby?
Official site: https://ruby-lang.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 Rubyand you'll see the exact version pulled from the bundled package.json when sourcemaps are exposed.