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JsDelivr Logo.svg
Developer(s)Prospect One, Dmitriy Akulov
Initial release2012
Operating systemCross-platform
TypeFree CDN

JSDelivr (stylized as jsDelivr) is a free public CDN for open-source projects.

It can serve web files directly from the npm registry and GitHub repositories without any configuration.[1][2]

It is currently the second most popular public CDN that hosts multiple projects.[3][4] On October 14, 2020, it became the official CDN of Bootstrap.[5]


jsDelivr also has an API for developers,[6] no traffic limits and is accessible worldwide, including from mainland China.[7] The project is sponsored by multiple notable companies like Cloudflare, Fastly, StackPath, appfleet, NS1 and DigitalOcean.[8][9] As of September 2017, the most popular hosted project there was slick-carousel with 3.7 billion monthly requests.[10][11]


The project makes use of two DNS providers for DNS redundancy. Due to round-robin if a single provider goes down the second will keep the CDN online.

A custom system hosted by appfleet analyzes the performance of the underlying CDN providers and pushes routing rules to the DNS providers to achieve better performance and uptime. Users get routed to the best performing and available CDN based on their location.[12][13]

The Chinese CDN provider Quantil is used to serve Chinese thanks to the ICP license held by jsDelivr.[14]

On the backend jsDelivr operates multiple clusters in Germany and The Netherlands that run the logic that powers the service. All served files are cached on the origin servers on SSD disks. Locally un-cached files are first fetched from a permanent cache hosted by Amazon S3. If the files are not present there then they are fetched from NPM or GitHub based on the type of request. After the first fetch all new and unique files are permanently cached on S3 to broken URLs due to deleted or renamed packages. In case of S3 downtime the permanent cache logic temporarily bypassed and files are fetched directly from NPM and GitHub.[12]


  1. ^ jsdelivr: A free Open Source CDN for webmasters and developers, jsDelivr, 2017-10-29, archived from the original on 2017-10-09, retrieved 2017-10-30
  2. ^ "Why jsDelivr Uses 2 DNS', 4 CDNs, and Fly". Fly Articles. 2017-10-06. Retrieved 2017-10-30.[permanent dead link]
  3. ^ "jsDelivr – The advanced open source public CDN". Mozilla. Archived from the original on 30 October 2017. Retrieved 29 October 2017.
  4. ^ "Usage Statistics and Market Share of JavaScript Content Delivery Networks for Websites, September 2017". w3techs.com. Archived from the original on 2019-04-12. Retrieved 2017-09-05.
  5. ^ "Bootstrap tweet announcing the new CDN". Twitter. Retrieved 2020-10-14.{{cite web}}: CS1 maint: url-status (link)
  6. ^ Greasidis, Thodoris (2016-02-26). jQuery Design Patterns. Packt Publishing Ltd. ISBN 9781785885129.
  7. ^ "Top 4 CDN services for hosting open source libraries". Opensource.com. Archived from the original on 2019-04-18. Retrieved 2017-09-07.
  8. ^ "Damit euer Code richtig gut aussieht: Open-Source-Font Hack in neuer Version veröffentlicht" [So your code looks really good: New version of open-source font hack released]. t3n News (in German). Archived from the original on 3 July 2017. Retrieved 29 October 2017.
  9. ^ "Interview with driving forces behind web dev projects jsDelivr & jSter". pingdom.com. Retrieved 2021-11-03.
  10. ^ "Serving One Billion JavaScript Library Downloads". Algolia. 27 September 2017. Archived from the original on 30 October 2017. Retrieved 29 October 2017.
  11. ^ "jsDelivr - A free, fast, and reliable Open Source CDN". jsdelivr.com. Archived from the original on 2017-09-04. Retrieved 2017-09-05.
  12. ^ a b "How jsDelivr works". www.jsdelivr.com. Retrieved 2020-10-13.
  13. ^ jsdelivr/jsdelivr, jsDelivr, 2020-10-13, retrieved 2020-10-13
  14. ^ "jsDelivr - A free, fast, and reliable CDN for Open Source". jsDelivr. Retrieved 2020-10-13.

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