cdnjs Technology Intelligence

What is cdnjs?

cdnjs is a free, open-source CDN hosting over 4,500 JavaScript and CSS libraries. Powered by Cloudflare's global network, cdnjs serves 200+ billion requests monthly, making it one of the largest JavaScript CDNs. Libraries range from jQuery to React to niche tools used by thousands of sites.

Founded in 2011 by Ryan Kirkman and Thomas Davis, cdnjs was acquired by Cloudflare in 2019 to ensure long-term sustainability. The service remains free, with Cloudflare providing infrastructure. Community members submit and maintain library updates via GitHub pull requests.

cdnjs hosts multiple versions of each library, serves both minified and unminified files, and provides SRI (Subresource Integrity) hashes. With 310+ Cloudflare edge locations, latency is minimal regardless of user location.

cdnjs Infrastructure

URL Structure: https://cdnjs.cloudflare.com/ajax/libs/{library}/{version}/{file}. Example: cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js

API Access: cdnjs provides a JSON API for programmatic library search. Query api.cdnjs.com/libraries?search=react to find libraries matching criteria.

SRI Hashes: Every file includes SHA-256, SHA-384, and SHA-512 hashes. Copy directly from cdnjs.com or API response. Verify integrity in browsers supporting SRI.

Auto-Updates: Bot monitors npm for library updates. New versions appear on cdnjs within hours of npm publish. Manual submissions via GitHub for non-npm libraries.

Cloudflare Network: Files served from 310+ edge locations. HTTP/2 and HTTP/3 support. Brotli compression. Aggressive caching with long TTLs.

Reliability: 100% uptime SLA backed by Cloudflare. Global anycast routing survives regional outages. Enterprise-grade infrastructure at no cost.

cdnjs Use Cases

Production Websites: High-traffic sites use cdnjs for library delivery. Cloudflare infrastructure handles scale. Lower origin bandwidth costs.

Development & Prototyping: Quick access to any library version without npm install. Test library upgrades by changing URL version number.

Documentation Sites: Library documentation often embeds working examples. cdnjs provides consistent, reliable library delivery for demos.

CodePen/JSFiddle: Online code editors default to cdnjs. Share examples with guaranteed working library links.

Static Sites: Jekyll, Hugo, or plain HTML sites without build processes use cdnjs directly. No bundler configuration required.

WordPress/CMS: Themes and plugins reference cdnjs for dependencies. Reduces hosting bandwidth. Works when self-hosting isn't possible.

cdnjs Implementation

Script Tags with SRI

<!-- React with SRI -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/18.2.0/umd/react.production.min.js"
        integrity="sha512-8Q6Y9XnTbOE+JNvjBQwJ2H8S+UV4uA6hiRykhdtIyDYZ2TprdNmWOUaKdGzOhyr4dCyk287OejbPvwl7lrfqrQ=="
        crossorigin="anonymous"
        referrerpolicy="no-referrer"></script>

<!-- Axios -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/axios/1.6.2/axios.min.js"
        integrity="sha512-b94Z6431JyXY14iSXwcYCuTRSiFEqdwpI/fTs0ZpfM+RBKrC6k+=..."
        crossorigin="anonymous"></script>

<!-- Animate.css -->
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/animate.css/4.1.1/animate.min.css">

API Query

// Search for charting libraries
fetch('https://api.cdnjs.com/libraries?search=chart&fields=name,version,description')
  .then(r => r.json())
  .then(data => {
    data.results.forEach(lib => {
      console.log(`${lib.name}@${lib.version}: ${lib.description}`);
    });
  });

cdnjs Advantages

Massive Library Selection: 4,500+ libraries covering every JavaScript and CSS need. From mainstream (React, Vue, Angular) to specialized (D3 plugins, PDF.js, highlight.js).

Cloudflare Infrastructure: Enterprise-grade CDN at no cost. 310+ edge locations. HTTP/3, Brotli compression, instant purging. Same network serving 20% of the web.

100% Free: No accounts, no API keys, no rate limits, no tracking. Cloudflare sponsors as community service. Sustainable long-term with corporate backing.

SRI Support: Every file has integrity hashes. Copy from website or API. Protect against CDN compromise or MITM attacks.

Version Availability: Multiple versions preserved. Test upgrades safely. Rollback by changing URL. Old versions remain available indefinitely.

Community Maintained: Open-source repository on GitHub. Submit missing libraries. Report issues. Transparent maintenance process.