Everything to know about cdnjs, the free open-source CDN for JavaScript and CSS libraries run by Cloudflare: history, features, usage, and how it works.
cdnjs began as a side project in January 2011, created by developers Ryan Kirkman and Thomas Davis who wanted an easy way for the web development community to load common JavaScript and CSS libraries from a fast, reliable, centrally hosted location instead of everyone self-hosting the same files repeatedly. The project's code was published publicly on GitHub on February 25, 2011, inviting community contributions almost from the start, which is part of why its library catalog grew so quickly in its early years.
Just months after launch, on June 15, 2011, cdnjs entered a partnership with Cloudflare, which provided the global CDN infrastructure needed to actually serve files quickly around the world, along with the now-familiar cdnjs.cloudflare.com subdomain. That partnership continued for roughly eight years until November 1, 2019, when Kirkman and Davis formally handed full ownership and day-to-day operation of cdnjs over to Cloudflare entirely, citing technical and commercial reasons tied to the project's scale. Since then, Cloudflare has run cdnjs as a fully free public service while the project's library list continues to be maintained through open, community-driven contributions on GitHub.
In practice, using cdnjs requires no signup, account, or configuration: a developer browses or searches the library catalog at cdnjs.com, copies the provided script or link tag for the specific library and version they need, and pastes it into their HTML. From that point forward, Cloudflare's globally distributed edge network handles caching and delivering that file to visitors from a nearby location, which typically improves load times compared to hosting the file on a single origin server, and it also means popular libraries are often already cached in a visitor's browser from having loaded the same file on another site using cdnjs.
Because the service is free, open source, and backed by Cloudflare's infrastructure rather than a monetized product with usage tiers, cdnjs is most commonly used for quick prototyping, learning projects, smaller websites without a modern build pipeline, and situations where a team wants to avoid bundling a large dependency into their own JavaScript build. Larger, more complex applications increasingly rely on npm-based bundlers instead, but cdnjs remains a staple reference point across tutorials, code examples (such as on CodePen or JSFiddle), and any project that wants to add a well-known library with a single line of HTML.
Yes. cdnjs is completely free and open source, with no signup, subscription, or payment required. It is funded and operated by Cloudflare as a public service to the web development community.
Cloudflare has fully owned and operated cdnjs since November 1, 2019, when original creators Ryan Kirkman and Thomas Davis formally transferred the project to them, citing technical and commercial reasons. Cloudflare had been cdnjs's infrastructure partner since June 2011.
cdnjs was created in January 2011 by Ryan Kirkman and Thomas Davis, with the project publicly launched on GitHub on February 25, 2011.
cdnjs has hosted over 4,000 distinct JavaScript and CSS libraries as of the last widely cited figures, with the catalog continuing to grow through community contributions on GitHub.
Visit cdnjs.com, find the library and version you need, and copy the provided script or link tag into your HTML file. No account or installation is required, and Cloudflare's CDN handles delivery automatically.
cdnjs, jsDelivr, and unpkg are all free, open-source CDNs for JavaScript and CSS libraries with broadly similar purposes. cdnjs is distinguished by its long operating history since 2011 and its direct operation by Cloudflare's infrastructure.
Yes, many production websites use cdnjs, particularly for well-known, stable libraries, though many modern applications increasingly use npm-based bundlers for more granular version control and to avoid third-party request dependencies.
cdnjs has been reported to serve over 200 billion requests per month and is used on more than 12 percent of all websites, reflecting its scale as one of the most widely used CDNs for open-source libraries.