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How ad blocking impacts your analytics data

How ad blocking impacts your analytics data John Greer
Ad blocking on mobile has been a big topic lately, but mostly from the impact these tools have from a display advertising perspective. Obviously, the ads themselves are a pretty important element. On top of that, however, marketers should be aware of the analytics and tracking impact many ad blockers have on any site, not just publishers.

Many of the most popular apps not only block ads, but block web analytics tools such as Google Analytics from tracking users at all. This means that marketers have no visibility or data around a growing portion of the visitors and sales on their site.

What's changed?

Apple began allowing ad blockers on Sept. 16, 2015, and they've been among the top apps in the app store since then. Mobile analytics platform TUNE estimates (survey data) around 22 percent of iPhone users and 27 percent of Android users block ads in some form currently. PageFair estimates about 2 percent of U.S. smartphone users use ad blocking.

With the introduction of ad blocking by Apple, they introduced a few powerful methods for a developer to block content:
  • Block by name - e.g., block any scripts, cookies, etc. that contain "analytics"
  • Block by site - e.g., any links, images, etc. from Buzzfeed.com
  • Block cookies - e.g. block all cookies from DoubleClick
While iPhone users have been able to block cookies previous to iOS 9, it's a bit of a clunky process and not an ad blocker. However, when cookie blocking is enabled, the default Google Analytics setup doesn't work. Browser apps that block ads are also popular, especially on Android.

For example, one of the most popular iPhone ad blockers, 1Blocker, allows you to block one type of media for free, with multiple configurations requiring an additional $2.99 in-app purchase.

By default, 1Blocker blocks all "Trackers." This includes a whole host of Google Analytics related tags, as well as Adobe SiteCatalyst, and Google Tag Manager.

When this app is activated on the phone, it has the effect of turning your site visitor into a virtual ghost, invisible to any and all tracking on your website. This goes beyond referrer data being stripped away, or paid & search traffic being bucketed into Direct to Site. This won't even result in a visit at all - complete invisible unless you feel like crawling through server logs or performing revenue reconciliation on a daily basis.

Here is where the bad news gets even worse -- 1Blocker isn't, by any means, the only app out there that does this. Most ad or content blockers use the exact same form of anonymizing your site visitors, and based on the survey from TUNE, that could equate to more than 20 percent of mobile traffic you're not reporting.

Estimating the missing data for your site

Marketers rely on tracking to make decisions, so it's important to at least get an idea of how much traffic you simply aren't seeing. We do have a few ways to estimate or even dig into this "dark traffic."

We're focusing on Google Analytics or Adobe Analytics traffic from iPhones here, but these concepts can be applied to other platforms as well.

Internal data sources
Visitors to a site leave all sorts of traces of their visit on the servers themselves, even when ad blockers are in place.

Potential sources
  • Server logs: Traffic is often logged on the server, meaning that a record of all visits can be looked at. Server logs aren't simple to access and the data is stripped down to the basic hit information.
  • Backend orders: Your internal databases contain every purchase order made on the website. A review performed on one client site showed a 3% variance timed with the ad blocking launch.
  • CRM data: Your internal databases should contain every email subscription made on directly on the website.
How to use the data
  • Pull the logs, orders, or emails from above and compare before and after Sept. 16th.
  • Tally the hits, orders, or emails and compare these numbers with your Google or Adobe Analytics count of pageviews, orders, or email sign-up goals to see if the variance grew after the launch.
  • That should give you an idea of how many iPhone visits are "dark."
Deep-dive into your analytics data
Trending your Google or Adobe Analytics data around that September launch can reveal some of the drop-off. Plot iOS versus Android traffic lines. Plot iOS Safari against iOS Chrome. Plot desktop Safari against mobile Safari. Adobe has a great video on how to do this with Adobe Analytics.

A comparison of 60 days before and after the launch of iOS9

The relative change post-launch can get you an estimated percent of dark traffic. We did this on several sites and found trends did indicate that a modest percent (1-4 percent) seems to now be missing. Any of these can specifically be impacted by outside factors, but as a whole there's a definite pattern.

An example of the opposing trend lines before and after launch

Write some code

A bit of JavaScript added to your website can help estimate when users have a content-blocking app installed. These two articles outline several ways this code could be written.

Looking inside the dark traffic

Server-side analytics
Simply seeing the size of the slice you are missing doesn't tell you anything about the contents of that pie (the ingredients, if you stick with the pie metaphor). Using server logs, server-side analytics tools such as AWStats and Webalyzer don't offer same reports that Google Analytics does, but they won't be affected by ad blockers. While this piece of total traffic may be small, they can let you see if these users behave differently on your site.

Jonathan Hunt is senior SEO account lead at PMG and co-authored this piece.

John Greer is a Senior E-Commerce Analyst at PMG. He serves as the client strategy lead for SEO and optimization opportunities in analytics, local, usability, and content. Over the course of his 17-year career, John has helped major brands like...

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