CDNJS Script Loader is a lightweight, intelligent WordPress plugin that allows you to load JavaScript libraries from CDNJS - the world's largest CDN for web libraries. Unlike bloated performance plugins, CDNJS Script Loader focuses on one thing and does it well: smart CDN management with automatic fallback.
- Lightweight: Single-purpose plugin without unnecessary features
- Intelligent Fallback: Automatically falls back to local copies when CDN fails
- Performance Monitoring: Real-time tracking of CDN performance and reliability
- Security First: Automatic SRI (Subresource Integrity) hash validation
- Dependency Safe: Preserves WordPress script dependencies
- Simple Interface: Clean, intuitive admin UI with tabs
- ✅ Easy Library Management: Add JavaScript libraries from CDNJS with just name and version
- ✅ Custom Filenames: Support for libraries with non-standard file naming, including nested paths such as
js/bootstrap.min.js - ✅ SRI Hash Validation: Subresource Integrity hashes from CDNJS, checked against the served file before use
- ✅ Dependency Preservation: Updates the existing script registration in place, so dependencies, placement, inline scripts and translations are kept
- ✅ jQuery Aware: Configuring
jqueryreplaces WordPress'sjquery-core, so jQuery is not loaded twice and jQuery Migrate keeps working
- ✅ Automatic Detection: Detects CDN failures (network errors and SRI mismatches) with an
onerrorhandler on the CDN script tag - ✅ Local Upload: Upload and manage local fallback copies
- ✅ Failure Tracking: Monitors and logs CDN failures
- ✅ Zero Downtime: Seamless fallback to local copies when CDN is unreachable
- ✅ Real-Time Metrics: Track load times using the Resource Timing API
- ✅ Failure Analytics: Monitor failure rates and last failure timestamps
- ✅ Status Indicators: Visual health indicators (Good/Warning/Critical)
- ✅ Performance History: Average load times per library
- Download the latest release
- Go to Plugins > Add New > Upload Plugin
- Upload the
.zipfile - Click Install Now and then Activate
- Download the plugin files
- Upload to
/wp-content/plugins/cdnjs-script-loader/ - Activate through the WordPress Plugins menu
cd wp-content/plugins/
git clone https://github.com/rafael-minuesa/cdnjs-script-loader.git- Navigate to Settings > CDNJS Script Loader
- Go to the Libraries tab
- Add your libraries:
- Library Name: e.g.,
jquery - Version: e.g.,
3.7.1 - Custom Filename (optional): e.g.,
jquery.min.jsorjs/bootstrap.min.js. Leave it empty to use the library's default file on CDNJS
- Library Name: e.g.,
- Click Save Libraries
- Go to the Fallback tab
- Enable Automatically load local copies if CDN fails
- Upload local copies of your libraries:
- Select the
.jsfile - Enter the library name (it must be a library configured in the Libraries tab)
- Click Upload Fallback File
- Select the
- Go to the Performance tab
- View real-time metrics:
- Total loads
- Average load time
- Failure count and rate
- Status indicators
- Reset statistics if needed
When a library's data is not cached yet, the plugin reads that version's file list and SRI hashes from the CDNJS API and then:
- Uses your custom filename, or the library's default file as published by CDNJS (falling back to the closest
.min.jsmatch) - Downloads the selected file once and attaches the SRI hash only when it matches the served file
- Caches the result for 7 days
If the API is unreachable, the plugin loads library-name.min.js (or your custom filename) without SRI and retries the API after one hour.
When fallback is enabled and a local copy has been uploaded, the CDN script tag gets an onerror handler. It fires on network errors and on SRI mismatches, reports the failure, and writes a new script tag for the local copy at the same position, so scripts that depend on the library still run in order.
<!-- Simplified output for jQuery -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.7.1/jquery.min.js?ver=3.7.1"
id="jquery-core-js"
integrity="sha512-..." crossorigin="anonymous"
onerror="this.onerror=null; /* report failure */
document.write('<script src="/wp-content/uploads/cdnjs-fallbacks/jquery.min.js"><\/script>')"></script>After each library loads, a small inline script reads its entry from the browser's Resource Timing API and sends the load duration with navigator.sendBeacon(), without blocking page load. Failures are counted by the fallback handler, so failure tracking needs fallback enabled and a local copy uploaded.
The tracking endpoints accept only POST requests for configured libraries with a valid duration.
- WordPress: 5.0 or higher
- PHP: 7.4 or higher
- JavaScript: ES5+ browser support
Yes, as long as the library is available on CDNJS. Search for your library there first.
If you've uploaded a local fallback copy, it will load automatically. If not, the script will fail to load (same as if it wasn't installed).
Generally, yes - in a positive way. CDNs are faster for most users, and the plugin only adds minimal JavaScript for fallback detection.
Yes! CDNJS Script Loader works alongside caching plugins. It runs at priority 999 to ensure compatibility.
Yes, when an SRI hash is attached. SRI makes the browser reject a file that has been tampered with. The plugin checks the hash CDNJS publishes against the served file and only attaches it when they match, so if CDNJS publishes a wrong hash for a file, that library loads without SRI.
Fixes and Hardening
- ✅ SRI hashes are now actually attached (the CDNJS API response was read incorrectly, so no SRI was ever added)
- ✅ SRI hashes are checked against the served file, so a wrong hash published by CDNJS no longer blocks a library
- ✅ The default file comes from CDNJS library metadata, and nested custom paths such as
js/bootstrap.min.jswork - ✅ Library data is cached per version and filename, and a failed API request is retried after one hour instead of on every page load
- ✅ The local fallback now loads on network errors and SRI mismatches, in the original script order
- ✅ Configuring
jqueryreplaces WordPress'sjquery-coreinstead of loading a second copy of jQuery - ✅ Existing script registrations are updated in place, keeping dependencies, placement, inline scripts and translations
- ✅ Load times are read from the Resource Timing buffer, so they are recorded reliably
- ✅ Saving the Fallback tab no longer erases the library list, and saving Libraries no longer resets the fallback setting
- ✅ Custom filenames added in new rows are saved and used, including on the first save
- ✅ Fallback uploads are limited to configured libraries, path traversal is blocked, and upload errors are reported
- ✅ Tracking endpoints accept only POST requests for configured libraries and return 400 or 405 for invalid requests
- ✅ Tested up to WordPress 7.1
Major Update
- ✅ Fixed critical bug with array handling in script replacement
- ✅ Added automatic fallback to local copies on CDN failure
- ✅ Implemented SRI (Subresource Integrity) hash support
- ✅ Added CDNJS API integration with caching
- ✅ New performance monitoring dashboard
- ✅ Tabbed admin interface (Libraries/Fallback/Performance)
- ✅ Local file upload and management
- ✅ Dependency preservation when replacing scripts
- ✅ Custom filename support for non-standard libraries
- ✅ Failure tracking and analytics
- ✅ Real-time performance metrics using the Resource Timing API
- Basic CDNJS URL replacement
- Simple admin interface
Contributions are welcome! This is an open-source project aimed at filling a gap in the WordPress ecosystem.
git clone https://github.com/rafael-minuesa/cdnjs-script-loader.git
cd cdnjs-script-loaderPlease report bugs and feature requests on GitHub Issues.
This plugin is licensed under the GPL-2.0+ License. See LICENSE for details.
- Author: Rafael Minuesa
- Website: prowoos.com
- CDNJS: Powered by Cloudflare CDNJS
- Documentation: This README
- Issues: GitHub Issues
- CDNJS Library Search: cdnjs.com
Made with ❤️ for the WordPress community