[froydnj]

(Disclaimer: I work for Mozilla.)

"Jank" is our internal term for slow, non-responsive interaction with the browser (the capitalization of it in the original message is a little peculiar). If you click your mouse button, and then a second or more later, the item that you were clicking on the screen responds? That's jank. That input form that's not keeping up with your typing? That's jank. And so on.

We can (and do) collect statistics on how much jank people are experiencing, and we can look for ways to improve those statistics, but knowing what particular sites (not complete URLs, just eTLD+1 sites) jank occurs on is much more actionable. Browser developers can go visit particular sites to experience and analyze the jank for themselves, or we can see what janky sites are particularly popular in a given region and focus our efforts on improving those sites--either by doing things more efficiently in the browser, or reaching out to the site developers and asking them to consider changing things to make their site work better in Firefox. (Complete URLs would be even more actionable, but we don't want to collect your complete browser history.)

The argument for Flash is similar: we can get aggregate usage numbers for Flash, and perhaps see how that correlates to jankiness (or crashiness, or what have you), but having some information on what sites are using Flash makes the data even more actionable, for similar reasons as those given above.

[SubiculumCode]

Spending resources optimizing Firefox for how sites implement their JS seems over the top. The heaviest sites tend to be the most mainstream anyway, imo, and those are easy to pick out.

I am a Mozilla supporter for more than a decade, but this is the wrong move.