# cdnjs, One of the Internet's Largest Open Source CDNs, Migrates to Cloudflare The CDN serving 9 billion daily requests has been rebuilt on Cloudflare's Developer Platform. - **Source:** [Cloudflare Blog](https://blog.cloudflare.com) - **Published:** 2026-07-30 - **Original article:** - **On Brifing:** https://brifing.si/s/b66b7996-f134-461e-ba96-a393a2c025c1 ## What is cdnjs? cdnjs is a free content delivery network for JavaScript and CSS libraries. Instead of self-hosting jQuery or Bootstrap, developers add a script tag pointing to cdnjs.cloudflare.com for instant global loading. Used by roughly 12% of all websites, cdnjs commands 48.3% of the JavaScript CDN market share. It's the backbone behind countless 'intro to JavaScript' tutorials, CodePen demos, and Stack Overflow answers. ## Massive Traffic Volume cdnjs serves an average of 9 billion requests daily, handling 108,000 requests per second across 330+ Cloudflare data centers. The system boasts an exceptional 98.6% cache hit rate. Particularly prevalent in educational content, it powers numerous coding tutorials and demonstration projects worldwide. ## Historical Evolution Founded in 2011 by Ryan Kirkman and Thomas Davis, cdnjs began as a free community mirror for popular open-source libraries. Cloudflare started hosting it months later at no cost and fully assumed maintenance in 2019. At that time, Cloudflare's Developer Platform wasn't mature enough to support cdnjs's entire ecosystem. ## AI's Unexpected Impact Today, LLMs like ChatGPT and Claude frequently use cdnjs when generating quick HTML demos. This stems from their training data containing numerous references to cdnjs.cloudflare.com. Fifteen years of blog posts, GitHub READMEs, and tutorials have established consistent, immutable URL patterns that models can reliably reproduce without hallucination. ## Security Advantages Every file on cdnjs includes SRI hashes, and the entire project remains open source. This immutable, hash-verified mirror provides crucial protection against growing supply-chain attack concerns. Remarkably, the service remains completely free—no registration or API keys required—a rarity in today's internet landscape. ## Migration Motivations Cloudflare migrated cdnjs not due to performance issues (98% cache hit rate, billions of requests, zero outages) but to enable future improvements. The previous architecture made implementing new features increasingly difficult, requiring coordination across GCP Functions, VMs, and Cloudflare for every change. ## Partial 2020 Migration In 2020, cdnjs partially moved to serverless architecture, transitioning file serving to Cloudflare Workers and KV. This significantly enhanced resilience and scalability while enabling Brotli and gzip compression for faster responses. However, the publishing pipeline (monitoring npm/GitHub for updates) remained on Google Cloud Platform. ## Legacy System Challenges The old system routed package updates through Cloud Functions, Google Cloud Storage events, Pub/Sub topics, a git-sync VM, and Workers KV—none sharing correlation IDs. Troubleshooting required manually stitching logs from GCP Logging and Cloudflare Logpush, with no unified view of pipeline state. ## Storage Complications Files existed simultaneously in Workers KV (with bare-metal fallback) and a GitHub repository as source of truth—neither fully authoritative. The ingestion pipeline comprised small GCP Cloud Functions chained together through object events, creating maintenance complexity. ## New Platform Capabilities After 15 years of development, Cloudflare's Developer Platform now maturely supports cdnjs end-to-end. Components like Workers, Workflows, D1, Queues, Cache, R2, KV, and Containers consolidate all system elements on one platform. This migration dramatically improves both observability and operational efficiency. ## Enhanced Observability The new system implements shared trace IDs throughout the entire pipeline. GCP Logging and Cloudflare Logpush data now correlate via common keys, enabling detection of partial successes—like when versions reach KV but silently fail to update GitHub. The system now understands complete pipeline state and generates appropriate alerts. ## Strategic Importance cdnjs's full migration to Cloudflare's Developer Platform represents a critical step for open-source sustainability. A free, unlimited, secure CDN service remains a rare internet commodity. This redesign ensures cdnjs can continue growing and serving as an essential resource through the AI era and beyond. ## Sources covering this story - https://blog.cloudflare.com/cdnjs-dev-platform-migration/ — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._