A recent exposure detected that Chrome and Chromium browsers down a “hotword” binary blob from the web which allows listening to microphone input of the user without her knowledge or consent. If you are not using a security-oriented browser like Tor or disabling JS everywhere this is a potential threat. Local Load is a Firefox extension that tries to reduce the chances.
Many webpages use JS libraries from googleapis.com. Though a major part of it is open source, the code is controlled by Google. Every time you fetch a library from there, Google knows which webpage you are visiting, which probably is NOT Google’s concern.
Local Load provides an alternative set of compatible libraries which is stored in your local system. It hooks into the web API calls to load these libraries. Beyond the obvious boost in security this also leads to faster page loading as the libraries are now loaded from your system directly. Local Load uses valid HTML5 compliant custom data attributes. All the JS libraries listed (at the time of writing) on Google AJAX Library APIs are supported.
Extension page: Local Load