An anonymous reader quotes ZDNet: A Mozilla engineer has revealed one of the hidden techniques that Firefox 57 -- known as Quantum -- is using to improve page load times... It delays scripts from Tracking domains, such as www.google-analytics.com. The technique was developed by Mozilla engineer Honza Bambas, who calls it "tailing". It works by delaying scripts from tracking domains when a page is actively loading and rendering... Tailing only briefly prevents the tracking scripts loading, rather than disabling them entirely. Page load performance is improved by saving on network bandwidth and computing resources while loading a page, in a way that prioritizes site requests over tracking requests. "Requests are kept on hold only while there are site sub-resources still loading and only up to about 6 seconds. The delay is engaged only for scripts added dynamically or as async. Tracking images are always delayed. This is legal according all HTML specifications and it's assumed that well built sites will not be affected regarding functionality," explains Bambas.
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