“"Google has removed important APIs with MV3, meaning this extension no longer works there." — LocalCDN project wiki, codeberg.org/nobody/LocalCDN/wiki (accessed June 2026)”
You know that feeling when you install an ad blocker, feel good about your privacy, then notice in the network inspector that your browser still phones Google, Cloudflare, and jsDelivr to fetch jQuery, Bootstrap, or Font Awesome? Those CDN requests are not ads, so uBlock Origin and Privacy Badger do not stop them by default. Every one of those requests gives the CDN provider a timestamped log of your browser, your IP, and the page you were on. Standard cookie blocking and fingerprinting protection do not address this tracking channel at all.
Think of LocalCDN as a local library that your browser checks first before calling out to the internet. When your browser tries to load jQuery from ajax.googleapis.com, LocalCDN intercepts the request before it leaves your machine, finds that library in its local bundle stored inside the extension, and delivers it directly — the CDN server receives zero bytes of the request. It uses Firefox's webRequest API with blocking mode, checking outgoing requests against a mappings.js file that lists URL patterns for 200+ libraries across 7+ CDN providers. An optional HTML filter mode strips integrity and crossorigin attributes from page HTML so LocalCDN can substitute even version-pinned libraries that would otherwise reject local copies.
If you use Firefox and care about privacy beyond what ad blockers provide — specifically if you have spotted CDN load requests in your network inspector that uBlock Origin leaves untouched — LocalCDN closes that gap with no configuration required. It also works as a practical audit tool if you build web apps and want to inventory which external CDN calls your own product makes. It is not useful if you primarily use Chrome, Edge, Opera, or Safari: Manifest V3 eliminated the Firefox-specific API that makes this work, and no Chromium port exists.
LocalCDN is production-stable: 6 years of active development, 18,278 Firefox users, 4.8/5 stars across 260 reviews, and quarterly releases from a responsive solo maintainer with a 9 open vs. 1,650 closed issue ratio. The privacy gap it addresses is real. The constraint to accept before installing: Google Fonts — the single most common CDN tracking vector on the web — cannot be bundled due to Mozilla's 200 MB extension size limit, so the largest threat remains unaddressed. If you are a Firefox user who wants everything-but-Google-Fonts covered for free, install it today.
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