cdnjs is a free, open-source content delivery network (CDN) for JavaScript libraries, CSS frameworks, and web fonts, hosted by Cloudflare. Launched in 2011, it has become one of the largest and most popular public CDN services, serving billions of requests daily. cdnjs hosts over 4,000 libraries including jQuery, React, Vue, Bootstrap, Font Awesome, and virtually every popular frontend library. The CDN provides automatic updates, version management, and fast global delivery through Cloudflare's extensive edge network. All resources are served over HTTPS with SRI (Subresource Integrity) hashes for enhanced security. Using cdnjs can improve page load performance through parallel downloads, browser caching across sites, and reduced server load. The service is community-driven, with contributions managed through GitHub, and offers API access for programmatic library searches.