A free, fast, and reliable Open Source CDN for npm and GitHub
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README.md

jsDelivr - Open Source CDN

Related projects:

We are looking for contributors. Please check open issues in the above repos if you think you could help, or open a new one if you have an idea you'd like to discuss.

Note: Our backend changed. Learn how to use the new jsDelivr

jsDelivr is a free CDN for open source files. We are tightly integrated with Github and npm allowing us to automatically provide a reliable CDN service to almost every open source project out there.

We offer a stable CDN that can be used in production on popular websites with huge amounts of traffic. There are no bandwidth limits or premium features and its completely free to use by anybody.

How does it work - A simple infographic

Why jsDelivr?

Ready for production

Our public CDN is built to be used in production by even the largest websites. Everything is optimized and being constantly improved to offer all users maximum speed and uptime. Performance is monitored at all times, and we are always looking into new technologies and providers that may further improve our CDN. Downtime, timeouts or slow responses are simply unacceptable.

We do everything possible to ensure our CDN will NEVER break any websites regardless of use-case. If a file is available via our CDN we assume its used in production and make sure that file will continue to work no matter what.

This includes dynamic endpoints such as /npm/, /gh/ and /combine/. When a file is first accessed it gets permanently stored in a reliable file system. This means that even if a npm package gets deleted, or an existing file gets removed by a developer, jsDelivr will continue to serve the stored copy for ever, without breaking any websites or causing any issues.

On top of that we also do version-fallback. This means that if a file used in version 1.0.1 is no longer available in 1.0.2 and a user requests the non-existant file we will fallback to the previous 1.0.1 version and serve it instead of failing with 404 error.

Multi-CDN

Unlike the competition, jsDelivr uses multiple CDN providers, resulting in the best possible uptime and performance. We currently use MaxCDN, CloudFlare, and Fastly. In mainland China we use Quantil.

If a CDN goes down, websites that use jsDelivr won't have any issues because all traffic will be instantly redirected to remaining operational providers.

Smart Load Balancing

jsDelivr uses Cedexis with real user performance data (also known as RUM) to make its routing decisions. These metrics are gathered from hundreds of websites and are used in our load balancing algorithm to make accurate decisions for serving content.

All providers (CDNs and custom servers) are tested millions times per day by real users from all over the world. Based on this information, jsDelivr knows what provider is the fastest for each user. Each user gets a unique response based on his or her location, ISP, and the providers' uptime in real time.

This system also responds immediately to performance degradation and downtime of providers. If a CDN is under a DDoS attack, and their performance drops in some locations, in matter of seconds the algorithm will pick up the change and start serving a different provider to all affected users.

Our load-balancing code is open source as well.

Failover

We have multiple layers of failover to protect our users from any downtime.

We use 2 DNS providers at the same time. For jsDelivr to go down both of these companies would have to go down at the same time.

Both of our DNS providers monitor our load-balanced endpoint and if they detect problems they will automatically switch all traffic to a single CDN provider.

Our load-balancer monitors the uptime of all CDN providers using both RUM and synthetic data. If any of those detect downtime or performance degradation that CDN provider will be removed immediatly without any impact to our users.

Our origin consits of multiple servers in different data-centers. If a server goes down the CDNs will automatically switch to using the remaining healthy servers.

In total we have one of the most resilient systems out there, ready to be used in production by even the biggest companies.

HTTP2

All of our POPs support HTTP2 offering better performance to all users.

China

jsDelivr has partnered up with multiple Chinese companies to provide fast and reliable file delivery in China mainland and the whole Asian continent. We have servers inside China that improve the delivery speeds and latency significantly. We also have a valid ICP license issued by the Chinese government that protects us from bans and slow downloads.

jsDelivr works perfectly inside China!

Usage

jsDelivr can instantly serve any file from any npm package in the public registry.

New versions pushed to npm are instantly available via our CDN as well. No maintenance is required.

If a package, version or file gets removed from npm then jsDelivr will continue to serve that file from our permanent storage without breaking any websites using it.

npm

Load any project hosted on npm:

/npm/package@version/file

Load exact version:

/npm/jquery@3.1.0/dist/jquery.min.js

Use a version range instead of an exact version:

/npm/jquery@3/dist/jquery.min.js
/npm/jquery@3.1/dist/jquery.min.js

Load by tag: (Not recommended for production usage)

/npm/jquery@beta/dist/jquery.min.js

Omit the version completely or use "latest" to load the latest one: (Dev environment only)

/npm/jquery@latest/dist/jquery.min.js
/npm/jquery/dist/jquery.min.js

Add ".min" to any JS/CSS file to get a minified version - if one doesn't exist, we'll generate it for you. All generated files come with source maps and can be easily used during development:

/npm/github-markdown-css@2.4.1/github-markdown.min.css

Omit the file path to get the default file. This file is always minified:

/npm/jquery@3.1.0
/npm/jquery@3
/npm/jquery

Get a directory listing:

/npm/jquery@3.1.0/
/npm/jquery@3.1.0/dist/

GitHub

Load any GitHub release or commit:

/gh/user/repo@version/file

Load exact version:

/gh/jquery/jquery@3.1.0/dist/jquery.min.js
/gh/jquery/jquery@32b00373b3f42e5cdcb709df53f3b08b7184a944/dist/jquery.min.js

Use a version range instead of an exact version (only works with valid semver versions):

/gh/jquery/jquery@3/dist/jquery.min.js
/gh/jquery/jquery@3.1/dist/jquery.min.js

Omit the version completely or use "latest" to load the latest one (only works with valid semver versions): (Dev environment only)

/gh/jquery/jquery@latest/dist/jquery.min.js
/gh/jquery/jquery/dist/jquery.min.js

Add ".min" to any JS/CSS file to get a minified version - if one doesn't exist, we'll generate it for you. All generated files come with source maps and can be easily used during development:

/gh/sindresorhus/github-markdown-css@v2.4.1/github-markdown.min.css

Get a directory listing:

/gh/jquery/jquery@3.1.0/
/gh/jquery/jquery@3.1.0/dist/

Combine multiple files

Our combine endpoint has the following format:

/combine/url1,url2,url3

All features that work for individual files (version ranges, minification, main modules) work here as well. All combined files come with source maps and can be easily used during development.

Examples:

/combine/gh/jquery/jquery@3.1/dist/jquery.min.js,gh/twbs/bootstrap@3.3/dist/js/bootstrap.min.js
/combine/npm/bootstrap@3.3/dist/css/bootstrap.min.css,npm/bootstrap@3.3/dist/css/bootstrap-theme.min.css

Publishing packages

All packages hosted on npm and tagged releases on GitHub are automatically available on jsDelivr. If you are a package author, here are a few tips to make using your package as easy as possible:

  • Use semver for versioning (this is enforced by npm but not by GitHub)
  • If a file listed as main in package.json isn't meant to be used in a browser, set a browser or jsdelivr field
  • If you distribute minified JS/CSS files, also include source maps for those files
  • If you don't want to provide minified files, it's fine - we'll handle that for you

Configuring a default file in package.json

For packages hosted on npm, we support serving "default" files with shorter URLs. The default file can be configured by setting one of the following fields in package.json, with jsdelivr having the highest priority:

  1. jsdelivr
  2. browser
  3. main

We will first attempt to locate a minified version of the file provided here (by removing the extension, and looking for the same file .min.js). If we can't find one we will minify ourselves.

Restrictions

  • Packages larger than 50 MB are not supported by default. We recommend removing files that are not needed from your package when possible. If you need to set a higher limit for your package, open an issue in this repo.
  • HTML files are served with Content-Type: text/plain for security reasons.

WordPress

Our WordPress endpoint works for plugins hosted in the WordPress.org plugin directory, and mirrors the WordPress.org plugins SVN repo has the following format:

/wp/project/tags/version/file

Load exact version:

/wp/wp-slimstat/tags/4.6.5/wp-slimstat.js

Load latest version: (Dev environment only)

/wp/wp-slimstat/trunk/wp-slimstat.js

Purge cache

jsDelivr has an easy to use API to purge files from the cache and force the files to update. This is useful when you release a new version and want to force the update of all version aliased users.

To avoid abuse, access to purge is given after an email request (for now - dak@prospectone.io).

Custom CDN Hosting

We can work together and setup a custom configuration for your project. This way, you can have full control over your files and the ability to utilize the full power of jsDelivr.

This kind of custom hosting can be suitable for:

  • Binary hosting. Windows executable files and zips.
  • Frequently updated files.
  • Projects that can't follow jsDelivr file structure.
  • Some other use that will blow all of our minds.

Simply send an email to dak@prospectone.io with a request for more information.

Current OSS projects using custom configs:

Contribute Performance Data

jsDelivr uses real user performance data (also known as RUM) to make its routing decisions. This data is gathered from hundreds of websites and is used in our load balancing algorithm to make accurate decisions based on real time performance metrics.

This is why we offer the ability to all users to help us out. This data is very important and we encourage all users to participate.

All you have to do is include the following JavaScript code in your website before </body>. This code is then executed each time a user visits your website. It uses their browser to test the latency to our CDN providers and gather performance and availability metrics.

These benchmarks are completely transparent to the user and do not impact on browsing in any way. We store the following information:

  • Performance metrics to each of our providers.
  • Availability metrics to each of our providers.
  • Browser’s User-Agent
  • First three octets of the user’s IP address

Our JS code is executed with a 3 second delay and tests all of our providers unless interrupted. This testing does not impact on your website performance or user browsing experience.

<script async src="https://rum.perfops.net/rum3.min.js"></script>

Privacy Policy

cdn.jsdelivr.net

jsDelivr might use information about downloaded files to build download stats per project and per file.

jsDelivr does not store any user data and does not track any users in any way.

Here are the relevant policies of our CDN providers:

The bus factor