Node.js
Node.js is an open-source, cross-platform, JavaScript runtime environment that executes JavaScript code outside a web browser.
What detecting Node.js tells you about a site
Node.js is a server runtime, so you do not see it in the page's client JavaScript directly — you infer it. The signals are server-side: an `X-Powered-By: Express` header, a `connect.sid` session cookie, Next.js/Nuxt SSR markers, or asset URLs served by a Node process rather than a CDN edge. Detecting it tells you the backend (or the SSR layer) is JavaScript, which usually means the same language spans the whole stack and the team can share types and tooling end to end.
Node.js in a real-world stack
When you find Node.js, it rarely travels alone. Express, Fastify, NestJS or Koa on the HTTP layer; very often a meta-framework (Next.js, Nuxt, Remix) owning both the server render and the client bundle.
About
Node.js is an open-source, cross-platform, JavaScript runtime environment that executes JavaScript code outside a web browser.
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 Node.js
Sourcemap Explorer carries 1 fingerprint signal for Node.js, spread across 1 channel — dom selector. 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.
A DOM selector that only this technology's pages render. Verified at runtime by the content script.
div.appVersion i.icon-nodejs
FAQ
How do I check if a website is using Node.js?
Open the page in Chrome, click the Sourcemap Explorer toolbar icon, and read the Stack tab. Node.js's specific fingerprints here are dom selector, and the popup flags Node.js whenever any combination of them is found. The same checks can be reproduced manually in DevTools — see the "How we detect" section above.
What Node.js version can Sourcemap Explorer detect?
Node.js 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 Node.js?
Official site: https://nodejs.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 Node.jsand you'll see the exact version pulled from the bundled package.json when sourcemaps are exposed.