Given we are discussing the top 100 websites, at the top e-commerce hosting platform - the question wouldn't really be to find out what websites were running Google ads, the question would really be to find out those that weren't.

So, I had to use some indirect thinking in this one.

There were no bulk tools that I could use to quickly check this, plus, Google's Tag Assistant chrome extension was just not running.

So I used Ghostery, a Chrome extension that is used to block ads and trackers, which also provides a list of every single tracking/advertising platform used by any website.

This was perfect because I needed to know which websites were remarketing to me using Google Ads.

So, I just bulk opened sites, and hand-checked all the 100 URL's.

It was a lot faster than I expected because all I had to find out was which one's weren't using any of Google's Advertising platforms.

The quick on-screen UI of Ghostery also helped for this task to be completed in (I think) less than 10 minutes.

So, here, have a backlink Ghostery: https://www.ghostery.com/