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Comment by was_boring | Hacker News Reader

Why is JavaScript required for ads?

It's not. It's required for tracking.

I run several websites where advertisers pay to be on the website so that their brand can be associated with the content, and get viewed — just like a billboard or a TV commercial. None of them have Javascript. They're just plain images and links.

You don't need javascript for tracking. You could just use an invisible pixel.

Some advertisers don't like to trust hits if they can't verify the hit came from a real, live browser. Like the difference between the original recaptcha (read the letters in this image) and the new ones (mouse, keyboard, and browser behaviour looks like a human browsing on a real browser).

In an absolute technical sense of course it isn’t, but virtually all the major players in web ads (Google Adsense etc) typically use JS to ship ads/tracking to your page.

It is not strictly required, but most ad networks want to know about you as much as possible, from display resolution to browsing history (if they can). This requires JS.

Also, a lot of ad content is "rich", animated, etc, also scripted.

In 1990s and early 2000s ads were mostly just images ("banners") served by an ad network, or even text links, without any scripting.

Because most ads are auctioned at the time the page is loading. The clientside scripts identifies the user however best it can and then contacts ad delivery networks to see who is willing to pay the most to place the ad (this is second hand recalling, I might be wrong)

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