The core idea behind the browser extension is to improve the page loading time of websites, and to improve user privacy by loading resources from the local system and not from remote locations.
We reviewed Decentraleyes for Firefox back in 2015 and found it to be an excellent add-on for this tasks as it improved the loading speed of sites that use included resources and the privacy as well.
The extension offers no 100% surefire way though as it limits resources that it can replace with local copies, and sites that it may replace these local copies on.
Basically, what it does is block requests to content delivery networks -- about ten or so are supported -- by redirecting the requests to the local resources. Resources that are supported by Decentraleyes include jquery, webfont, scriptaculous, modernizr, and angularjs.
Decentralyes was offered as a legacy add-on for the Firefox web browser up until now. While that version works fine currently, it will stop working in Firefox 57 and newer versions of the web browser. Mozilla plans to drop legacy add-on support in Firefox 57, and since Decentraleyes is offered as a legacy add-on currently, it will stop working.
Firefox 57 or newer will disable the add-on automatically after the upgrade, and there is no option in release versions of the web browser to re-enable these extensions.
The developers of the Decentraleyes extension have released a first version of Decentraleyes 2.0 Beta. This version is compatible with Firefox 57 and newer. While it is available as a beta version currently, the developers plan to make it available as a stable version before Firefox 57 is released.
This means that users of the browser extension will be able to use it when their Firefox browser gets updated to version 57.
The browser extension comes with two options currently: You can whitelist any domain to exclude it from inspection. The domain will load the resources from the content distribution networks as Decentraleyes will ignore it.
The second option is to block requests if local resources are missing.
Important add-ons like NoScript or uBlock get ported so that they are compatible with WebExtensions. Other important add-ons like Classic Theme Restorer or Down Them All won't be ported on the other hand.
The situation is uncertain for quite a few add-ons right now.
Now You: Do you use Firefox? How many of your add-ons are compatible with Firefox 57?