Download websites that use JSS

About JSS

Hardly anyone installs JSS deliberately. Something else brings it in, usually a React component kit that uses it as a styling engine, and that origin governs how a list of the sites carrying it should be read.

The library itself is straightforward. Released under the MIT license and dating from 2014, it lets developers describe styles as JavaScript objects and inject the resulting rules into the document at runtime. The approach solves a genuine problem in component based interfaces, where styles need to be scoped to a component, generated from its props, and removed when the component unmounts. For a stretch of frontend history that was the standard answer, and the library became the styling engine underneath widely used React component kits rather than a tool teams adopted on its own merits. A large share of installations are transitive dependencies pulled in by a UI framework, not a decision anyone made about CSS.

Detection is inferential and worth being honest about. What we match is the fingerprint of the library's output: generated class names with a recognizable shape and style elements written into the document head after load. Build pipelines that extract styles ahead of time, and configurations that supply a custom class name generator, can make a working install unrecognizable to us. As of October 2026 the figure stands at 238 sites, and the true number is higher.

Even with that caveat the population is a useful one, precisely because of what the dependency implies. A site carrying this Development is very likely a React application of a particular generation, built during the window when runtime CSS in JavaScript was the default choice in that ecosystem. Age of the codebase, framework family and probable rendering model all follow from a single detection, which is more than most frontend libraries tell you.

That makes the audience for the list fairly specific. Component library maintainers want to know how large the installed base under their own package really is. Agencies selling frontend modernization want a list of applications built on an approach the ecosystem has largely moved past. Performance tooling vendors care because runtime style injection has a measurable cost on first render, and the sites paying that cost are the prospects.

A per domain lookup answers whether one site uses the library today. The dataset answers which cohort of applications was built on this stack, how it distributes across countries and top level domains, what else those applications ship alongside it, and, compared between snapshots, how quickly teams are migrating away from runtime styling toward compile time alternatives.