Event Tracking & how it affects your Analytics Data

Event tracking in Google Analytics is extremely robust and with the Universal Analytics measurement protocol, can be configured to measure pretty much anything. Video views, document downloads, signups, link clicks and a whole lot more can be tracked in events which, no doubt, is great.

In this article I’m not going to talk about how to use events or how to set them up, I’m going to look at the bi-products of setting up and tracking events. When I say bi-products I mean stuff that happens that you don’t expect as a direct result of implementing the Event tracking.


You will soon find out that the changes you make it do not happen in isolation and can lead to a complete change to the makeup of your traffic analysis. Scary and confusing at first but it makes sense.. just stick with me for a little.

So to avoid the head scratching when you do in fact implement all your event tracking, I’m going to look into some elements that you may want to keep a close eye on post implementation.

What is an Event in Google Analytics?

As mentioned earlier, event tracking allows us to track specific events whether it be a video view, download or whatever. But what actually is an Event?

Google defines it as the following:

Events are user interactions with content that can be tracked independently from a web page or a screen load. Downloads, mobile ad clicks, gadgets, Flash elements, AJAX embedded elements, and video plays are all examples of actions you might want to track as Events.

Hey Will.. It’s like the third time you’ve mentioned this.. whats your problem?

I understand but can you see what I did in the definition above? I highlighted the fact that events are in fact simply, user interactions.

Adding event tracking will measure user interactions with your site. Previously if you do not have events set up the interactions are limited to clicks through to other pages within your site, also known prehistorically as ‘hits’. Yes its truly a prehistoric term that should stop being used.

Now lets look at the definition of what a ‘Session’ is in Google Analytics:

A session is a group of interactions that take place on your website within a given time frame.

Do you see where I am getting at here?

With the implementation of event tracking you are effectively tracking more of what the user does known as user interactions, (deliberately highlighted twice) which in turn flows through to the rest of your analytics data, notably your sessions.

Stay with me now as I dig a little deeper and show you some examples.

Event tracking and Bounce Rate

One area you will notice the biggest change will be your bounce rate. In most cases, it will plummet. See example below:

event tracking and bounce rate

For these guys we implemented event tracking across multiple areas of their site, some of which included form downloads as well as action items which moved them off the site onto another site.

If we look at what bounce rate really is we can draw the conclusion quite quickly as to why this happened.

Google defines bounce rate as:

Bounce Rate is the percentage of single-page sessions (i.e. sessions in which the person left your site from the entrance page without interacting with the page).

There is it again! Can you see it? You see, when you create events you are measuring interactions. Since a ‘bounce’ is recorded whenever someone lands on a page and then leaves without interacting, then naturally if more interactions are made then the bounce rate will drop.

I’ll give you an example.

Before implementing event tracking – a user has visited your website and landed on the page where there is a sale brochure for them to download. They read the content on the page, download the brochure and then leave. Without even tracking this user is effectively a ‘bounce’ because no interaction was triggered.

After implementing event tracking – Consider the above scenario. If event tracking was implemented then the brochure download would have been recorded as an event (ie an interaction). Suddenly the same user, doing the same thing, does not ‘bounce’.

That shows how the exact same user journey can be both regarded as a bounce as well as an engaged user all due to event tracking.

Event tracking and Pages per Session

event tracking and pages per session in Analytics

This is a little more tricky as an ‘event’ is usually not considered a ‘page’ visit unless you have set it to be. What we need to remember is that it all comes down to how a ‘session’ is calculated.

With sessions now having more interactions within them (due to recording events), a user is effectively ‘active’ for longer. This means that there is a lower probability of a session timing out, hence more pages per session as bi-product of that.

The change in Pages per Section is unlikely to be display an extreme shift in or drastic change in user behaviour such as what we saw with bounce rate but you will most often notice a change… or to be more accurate, a reported change in user behaviour.

Event tracking affect on Session times

You are probably already making some mental notes that number of sessions, pageviews and avg. visit duration would also experience some shifts.

Well what we need to remember is that implementing event tracking and increasing interaction tracking doesn’t change the way a user interacts with the website. A user browsing a website would have no idea of the extra tracking completely and their behaviour will not change at all.

Session duration can go either way. It could either stay roughly the same because the user will still stay on the site for the same length of time and visit the same number of pages. Or it could increase depending on when the interactions occur.


So it also depends on the type of user interactions we are measuring. What effects the session duration is skewed proportionally to how the user journey generally ends.

If the final interaction is usually an ‘event’ then the time on site may increase a little. If the final interaction is a page visit then you will barely notice any change in session times.  This is because Google Analytics session times work on a last interaction timing, with an interaction being either a page ‘hit’ or an event ‘interaction’.

So lets look at this example of how Google Analytics measures session duration with and without event tracking implemented. The one at the top shows session time calculation without it and the one at the bottom shows it with the tracking implemented:

Calculating session duration google analytics

In the example above we can see that even though event tracking was installed the session time was exactly the same.. 15 minutes.

However if the user did not visit page 2 then it would be completely different. The user would have bounced without the event tracking (with a 0:00 time per session) compared to the event tracking version, which would have been a 10 minute session that didn’t bounce. Makes sense?

Whether session duration actually changes really depends on how people interact with the site. Measuring before and after will give you added insight to your user journey outside of measuring events just by looking at session duration.

Event tracking affect on Pageviews

Pageviews you ask? Well remember what we discussed in that the users still do the same things. By implementing event tracking it will do absolutely nothing to the ways users interact and use your your website.

Tracking as a default measures page views as the indicator of activity through a website. A user will naturally visit the same number of pages whether events are firing or not, therefore there should be very little change in the pageviews metric. You can see this in the example below:

event tracking and pageviews analytics

Tracking the changes

We now know that tracking events in Google Analytics is not an isolated change and it in fact travels through and affects the rest of the data in one way or another. The degree of effect is dependant on how users travel through and use a website.

What you can do however is ensure that you track changes to your Analytics by taking some very simple measures.

The easiest and most effective way to keep track is to annotate every amendment you make in the Analytics account, view or property.

Some changes you make won’t have an effect at all but regardless, keeping tracking of changes is vital. An annotation only take seconds.. just click the little arrow down and your are on your way.. see below:

annotate in analytics

You have seen these little speech bubble icons in my examples above as I use them for pretty much anything I do.


Event tracking is vital to better understand your traffic. It can give you great insight into what your users are doing on the site and improve the metrics that Google Analytics gives you.

What you need to ensure is that you understand the effect it may have across your entire view. You may even want to create a new view for the event tracking version of analytics reporting (understanding that historical data will be lost) or you could annotate and keep track of the reporting shifts that will occur.

Hopefully now you will be left with fewer surprises when the phone rings and the client has some puzzling questions you need to answer.