There could be various reasons:
* strong Same-Origin-Policy (serverside)
* crossorigin/integrity attributes (serverside)
* ServiceWorkers (serverside)
* missing frameworks (LocalCDN)

You can test a website online or manually:
* https://www.localcdn.org/test/check

You can always report the website as an issue at codeberg or by e-mail. Then I could see what the problem is and improve the extension:
* https://codeberg.org/nobody/LocalCDN/issues
* https://www.localcdn.org/contact

Thanks for your feedback :)

I have created an issue on Codeberg and already made a few adjustments. I would be happy if you would test it :)

https://codeberg.org/nobody/LocalCDN/issues/257

Thank you for the great feedback. I'm very happy if you are satisfied with the extension :)

I'm glad if you like the extension :) Thank you. I wish you the same (belatedly) and a good start into the new year ;)

Thanks for your feedback. Normally upgrading within a major line (v5.x or v4.x) isn't a problem. But unfortunately there are exceptions, e.g. jQuery. I could add a option to disable upgrades, but if you load a framework from a CDN, you can load more from there. There you can also use the whitelist directly and disable the extension for a domain. It would be great if you report these sites, then I can look at it and improve the extension.

Thank you very much for your feedback. It's difficult to decide which default setting is best for Google fonts. I'll think about this point. Thanks :)

Many thanks :)

Thank you very much for your feedback :)

Thanks for your feedback. I'm glad that you like LocalCDN :)