Measure the impact that MarTech has on your site

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Folks often take for granted that they “must” have analytics and martech tracking and tools on their site. And that may be true, but that doesn’t mean we shouldn’t try to minimize the impact… because it DOES have an impact. I looked at the home pages of 5 brands from the top of the Fortune 500, and found that:

  • On average, 35% of the page weight was for MarTech. (Note, this does include stuff beyond just conversion pixels… it’s tag managers, optimization tools, analytics, consent management… some of which may improve the user experience, but none of which is required for the site to function.) For the Telecom site, literally half of the site weight was marTech!
  • Tag Manager Containers alone can carry a lot of weight- for the Energy site I looked at, it was 15% of the site’s total weight! I mention this in my post about TMS Best Practices, but an EMPTY Google Tag Manager container weighs 30-40 kilobytes (not to compare, because weight-when-empty isn’t the most useful measure, but an empty Adobe Launch library is 9 KB). If you add a single Google Adwords Conversion tag using GTM’s Tag Template, that adds another 20 KB. That’s more than any script on my site, including the whole jQuery library. A “full” TMS library can easily be the “heaviest” single asset on a page.
  • All that marTech tagging also means a lot of different domains are contributing something as the page loads. The Media site I looked at had almost 200 different third-party domains adding their script, pixels or iframes to the page.
  • MarTech DOES impact page speed in a way that. That media site had a speed index of 13.2 seconds for a mobile device (meaning it took about 13 seconds before the majority of VISIBLE content on the site was loaded.)

See the impact of your TMS on YOUR site with Chrome Developer Tools

If you want to get a quick sense of the impact marTech has on your site, there is an easy way to do it using the Chrome Developer console. I find the easiest way to get to the Dev Console is to right-click anywhere on a page and choose “inspect” (you can also do Ctrl+Shift+J on Windows or Ctrl+Option+J on a Mac). Once in there, go to the network tab (#1) and find your main TMS container file. You can use a filter (#2) to get to it quickly: adobedtm.com or launch for Launch, googletagmanager.com or gtm for GTM, or utag for Tealium. Right click on the first file that matches that filter (#3), and select “Block Request URL” (#4):

This essentially gives you an “ON/OFF” switch for your TMS:

You can load any page on your site with your TMS “on”, as it is for all your users, then turn your TMS “off” and see the difference in load times and amount of files and weight on your site. The “DOMContentLoaded” and “Load” numbers at the bottom of the network window are good ones to watch, since they show the amount of time for the main structure of your site to be built, and the time for images and other content to load.

Do make sure you’re comparing apples to apples- either use a fresh incognito window for each load, or click the “Disable Cache” checkbox in the network tab (#5 in the graphic above).

For example, with the TMS in place, this particular site I tested took 3.5 seconds to load, and had 54 files (“requests”) with a total weight of 3.2 MB. (I tend to ignore the “KB transferred” and “Finish” numbers for reasons not worth going into).

After I “blocked” the TMS, those DOMContentLoaded and Load times went down considerably:

This isn’t a perfect science- every time a user loads a page they’ll get slightly different times depending on device, bandwidth, server response times, and caching- but it can give you a quick sense of how much your marTech and analytics scripts have on your site. If you want to take it a step further, you can use this “Request Blocking” trick while running a lighthouse test directly in your dev console:

Get deeper insight on the impact on your site with webpagetest.org and my marTech Governance and Impact template

If you want to dig deeper, I’ve developed an Excel template that uses webpagetest.org to export then analyze the domains that load resources on your site:

Deeper instructions are in the template itself, but at a high level: run a webpagetest.org scan of a page on your site- for instance, I ran a scan on marketingAnalyticsSummit.com. Once the scan has run, grab the URL and paste it in to cell B1, just for safekeeping (you can always refer back to it later). The “good stuff” is on the Domain tab, but if you’re interesting in overall metrics on the main page, you can throw this script in your developer console:

document.querySelectorAll("#tableResults tr")[0].remove() //clean up the table so we can copy the whole table but get only the row we care about
document.querySelectorAll("#tableResults tr")[0].remove()
copy(document.getElementById("tableResults")) //copy the table to your clipboard
document.location.href=document.location.href //refresh the page so you get the full table back

Then paste into cell A4 in the template (it’s bright yellow) to fill out this handy little table:

Next go to the domains portion of the scan:

Here you can see a nice view of all the different domains loading resources on your page.

In general, you can use the process of elimination to figure out what is from a marTech vendor… in most cases, if it isn’t a domain you own, it’s marTech (not always, but… often enough). Figuring out which marTech vendor can be a bit trickier. I mean, www.linkedin.com is pretty obvious, but LinkedIn also fires resources from licdn.com.

Over time, I’ve collected a mapping of domains to vendors that we’re making publicly available. It will never going to be comprehensive (the list of 9900+ marTech vendors is ever growing and changing) but it can at least serve as a starting point. If you have changes or additions, you can throw them on the un-curated (and publicly editable) version. Anyway, once you are on the Domains Breakdown part of your scan results, you can put this code into the developer console to copy the table on the right to your clipboard:

copy(document.querySelectorAll(".google-visualization-table-table")[1])

Then paste the result into cell A12 of the excel template (it’s red), which will fill out the table and allow it to check if domains match our list of known domain/vendor mappings, then summarize what it finds:

For instance, here we find that marketinganalyticssummit.com’s home page weight is 26% marTech (and 8% TMS). It’s a very light site to begin with, so 26% of not much is…. not much. But it’s interesting to see how much is going on behind the scenes, even on “light” pages.

Now that you’ve established a high-level view of marTech’s impact on your site, you may want to dive deeper and do a tag audit… I’ve got tips and tricks for how!

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