> How could we tell you that?

As you just said: a billion impressions aren't worth anything if it doesn't affect anything you measure. And that's the whole problem in the ad industry. Are you buying ads to:

- Build your brand/awareness/mailing list?

- Get marketing qualified leads that your sales will handle?

- Get sales for your SaaS without going through sales?

- Something else?

Each of these require different type of tracking - views, clicks, actions. More importantly though, each is subjected to ad fraud. And simple text/image ads won't let you detect the latter to weed it out of your stats.

And the event you're thinking "so? as long as your ROI is positive you're fine" the answer is no, it's not good, because it incites more fraud and the budget might have been better spent on content marketing or other efforts.

And none of that requires JS to be delivered to the browser beyond the script that loaded the ad itself. The ad networks should pass whatever appropriate data to each other, not the browser.