Dart
Dart is an open-source, general-purpose, object-oriented programming language developed by Google.
What detecting Dart tells you about a site
Dart on the web overwhelmingly means Flutter Web. The signature is unmistakable: a single `main.dart.js` bundle, a `flutter.js` loader, and a canvas-rendered UI that draws the entire interface with CanvasKit/WebGL rather than HTML elements. Detecting it tells you the site shares a codebase with a Flutter mobile app — the team built once and deployed to web, mobile and desktop from the same Dart source, prioritising cross-platform reach over web-native semantics.
The detail that matters for Dart
Whether the page renders via the HTML renderer or CanvasKit is the key nuance: CanvasKit gives pixel-identical cross-platform output at the cost of a larger download and weaker accessibility/SEO, which is a real trade-off worth spotting.
Dart in a real-world stack
When you find Dart, it rarely travels alone. The Flutter framework and Dart SDK; a shared mobile/desktop codebase behind the same app.
About
Dart is an open-source, general-purpose, object-oriented programming language developed by Google.
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 Dart
Sourcemap Explorer carries 5 fingerprint signals for Dart, spread across 3 channels — cookie, javascript global and script src url. 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.
Cookies set by the platform. Visible in DevTools → Application → Cookies.
DARTSESSID
Window-level global the technology installs on page. Reproducible by typing the path into the DevTools console.
window.$__dart_deferred_initializers__
window.___dart__$dart_dartObject_ZxYxX_0_
window.___dart_dispatch_record_ZxYxX_0_
Script URL pattern. Typically a CDN host or chunk path that ships with the technology.
/(?:\.)?(?:dart)(?:\.js)?/
FAQ
How do I check if a website is using Dart?
Open the page in Chrome, click the Sourcemap Explorer toolbar icon, and read the Stack tab. Dart's specific fingerprints here are cookie, javascript global and script src url, and the popup flags Dart whenever any combination of them is found. The same checks can be reproduced manually in DevTools — see the "How we detect" section above.
What Dart version can Sourcemap Explorer detect?
Dart 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.
Is Dart open source?
Yes, Dart is open source. The license details are listed on the official site (https://dart.dev), and the codebase typically lives on a public source-control host.
Where can I read more about Dart?
Official site: https://dart.dev. 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 Dartand you'll see the exact version pulled from the bundled package.json when sourcemaps are exposed.