Introduction To Marketing Technology Course

Piggyback and Container Tags

Beacons? Pixels? Tags?

What difference does a word make?

As it turns out, quite a lot! So, in what follows, I will highlight those key words, so that we pay attention to them!

I was new to the domain of adding conversion pixels to web pages. I was asked to find the mismatch between traffic numbers being reported by Sizmek and AKQA on Yahoo webpages.

I examined the page and did not see any image tags (<img) for Sizmek. I only saw AKQA image tags. For Sizmek, instead, I was seeing Javascript.

Even I knew that a pixel is an image, and in HTML, image is created by typing ‘<img’ , not by calling Javascript. What was going on?


I started googling, and taking a look at the documentation, and I had an AHA moment. The industry had a problem, and it had come up with multiple solutions.

Problem: The marketing team buys traffic from multiple networks. All those networks demand their own conversion pixel – the traditional 1×1 <img> variety. To place these on the pages, the marketing team had to contact the engineering team to make code changes for the web pages. This caused delay. People are aversive to delays. There was a problem.

Solution: What if the marketing team could make a one-time request only to the product team to put something like a Trojan Horse on the page. After that, the Marketing team could change what image tags were placed on the page without having to bother the engineering team.

Solution Technology: This was such a super hit idea, that entire companies arose to service these. However, each of these companies initially created their own technology. Some used javascript, while others used HTML, optionally with an iFrame. There would be a dashboard presented to the marketing managers – they could add in all the networks’ image tags in the dashboard and change them dynamically. Each time the iFrame or Javascript was loaded in the browser, it would download the latest set of image tags.


OK, now I was educated. I understood that Sizmek’s Javascript was being loaded on the pages. AKQA tags were being loaded by the Sizmek Javascript. The industry term for Sizmek Javascript was Container Tag. And for the AKQA pixel – piggybacked pixel. In addition to firing the Container Tag, the Yahoo properties had directly place a different AKQA pixel on the page. I was now comparing AKQA pixels to AKQA pixels – one directly on the page, and the other piggybacked on Sizmek Container Tag. There was a mismatch of 50%. AKQA images directly place on the page were firing twice as often as those piggybacked on Sizmek.


Tremendous amount of debugging occurred. I escalated the issue to involve Sizmek CTO. He came on call, understood the issue, and provided maximum support. I asked Sizmek team to provide us with their raw logs – they did – and it looked OK. I asked them to create a new server on a different CDN and did a test. They did, and still the problem persisted. We tried Javascript, we tried iFrame. The mismatch refused to go away.

One day, a Sizmek engineer hypothesized that it could be an Ad Blocker issue. We downloaded the most popular AdBlocker. When we turned it on, we saw no Sizmek Pixel firing. Only the AKQA fired. When we turned the AdBlocker off, both fired. Bingo! Perhaps …

We were not sure how popular this Ad Blocker was – we googled – and found that more than 50% of the browsers had this installed! Bingo!

This is an open source Ad Blocker – so, we were able to look at the source code of the text file that determines whether a URL is an Ad. It is called EasyList. Sure enough, Sizmek pixels domains were listed as Ads.


An obvious question remained – why was Sizmek being blocked, but not AKQA or Google’s doubleclick.

The answer was that when serving Ads, and when firing conversion pixels, Doubleclick and AKQA were using different subdomains … and only the ad serving subdomain was blocked.

For Sizmek, there was only one common domain between ad serving and conversion. So, when Ad serving was blocked, so was the conversion!


We decided to create a new subdomain for Sizmek and use that. We made DNS entries in Sizmek. We changed our methodology on creating pixels. It was hell. But it worked. Until it didn’t. A month later, the new subdomain had been added to the Easy List.

It took more than a year for Sizmek to work it out with Ad Blockers team to have a separate entry for the conversion tags. In the meantime, we had moved on to a different vendor – Doubleclick – which did not have this issue.

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