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Difference in data collected from VWO and GA

Tuesday, January 28, 2014

VWO and Google Analytics (GA) have different tracking methods and you may find gaps between the data collected from these tools. An important point to note here is that GA is an analytics tool whereas, VWO is an A/B testing tool; and, each of them have different tracking methods. The following are some of the most commonly reported issues and their reasons:

'Visit Starts’ data in GA with ‘Visitors Data’ in VWO is different

'Visit Starts' data in GA is the total number of visits on the website. GA tracks all visits to a page (both first-time visitors as well as revisiting users).

Visitor count data in VWO only records first-time visitors who landed on the test page while GA tracks visits based on sessions. VWO creates a cookie for every visitor to recognize whether a user is a first-time user or a revisiting user. By default, VWO cookie remains active for 100 days and a repeat visitor is not recorded as long as the VWO cookie lasts in the user’s browser.

Situation - If a user visits your website, closes it immediately and revisits again after some time. 

  • GA starts a new session for each visit of the user 
  • VWO records only the first visit of the user. In this case, the ‘visit starts’ data in GA will report 2 visits.

Real-time Reporting

GA reports take 24-48 hours to update custom variable data. If you have pause a test, make sure that you wait for at least 48 hours to review the data. VWO reports provide real time data. You can view your test reports instantly in real time.

Comparing Date Selector Data in GA and VWO gives different figures

In GA, the date selector data displays unique visitors for the specified date range (even if a user may have visited the site just a day before the selected date). In VWO, the date selector data does not segregate unique visitors for a selected date range. It tracks unique visitors based on the VWO cookie added to the user’s browser.

Situation 1 - if a user visits a page (under test in VWO and also tracked in GA) on 4th May, 

  • The user is tracked as a unique visitor for 4th May in both VWO and GA. 

Situation 2 - If same user visits the site on 5th May

  • VWO will not consider it a unique visit and does not track the visit for 5th May. 
  • GA  records his/her as unique visitor.

So, if the date selected is 4th May, both VWO and GA tracks one unique visitor. However, if the date selected is 5th May, you will see zero unique visitors in VWO while GA will display it as one unique visitor. Now, if you select a date range of 4th -5th May, you will see one unique visitor in both VWO and GA.

Comparing Results in Different Time Zones

GA generates reports based on the time-zone you selected while creating the account. Make sure that your date range and time zones are same in both GA and VWO.

The default time-zone in VWO is GMT. You can change the default time-zone in VWO but all your previous data will display in the previous time zone. Only the new data you collected after changing the time-zone will be in accordance to the new time zone. Changing the time-zone in the middle of a test may create a huge data mess and may spoil the outcome of the collected data. We recommend that you do not change your time zone in between the tests, and wait for all your tests to complete before you switch your time zone.

You Have Multiple Tests Running at the Same Time

When you have multiple tests active on the same webpage or the same domain, make sure that you choose different slots in GA for each of your tests. If you are pushing the data for multiple tests in the same slot, your VWO and GA data will not match.

You want to run a split URL test without integrating VWO with GA

In a split URL test, the control page loads in the browser before the visitor is redirected to the variation page. Even before the redirection takes place, GA code begins to execute on the control page itself. This could trigger a pageview on the control page in GA. This occurs mostly because VWO’s code is asynchronous in nature and gets activated at any time on the web page (and not necessarily at the beginning of the page).

In a scenario where GA code is activated before the VWO code in a split URL test, anyone going to the variation will also be counted in the control’s pageviews as well. As a result, you’ll see that the pageviews for your control page are almost the double of your variation in a split URL test.

To solve this issue, follow one of the ways mentioned below:

  1. Place synchronous VWO code at the top of the head section of the page so that GA code is not executed until the redirect happens.

  2. OR

  3. Integrate the campaign with GA or UA, and create segments in your GA to avoid the visits of the variation page from being counted in your control page data.
  4. Your Bounce Rate is Going Down in GA, But Not in VWO

    In case of a split URL test, GA code may get activated on the page before the VWO code. In the process, it tracks the pageview of the visitor for the control page, before the visitor is redirected to the variation page. GA treats this redirection as an engagement because the visitor still stays on the same page even after being redirected to the variation. This may result in lesser bounce rate in GA. On the other hand, VWO does not track bounce rates.

    We recommend checking the bounce rate through custom variables in GA to know the accurate data. Use the non-interactive event in GA to make sure that Google does not count this redirection as engagement (or change your bounce rate) and only treat it as a pageview. As soon as the event is created, GA starts collecting the data accordingly. However, it may take 24-48 hours before this new data begin to reflect in your custom variables reports.

    You are Using the DoubleClick Code of GA for Tracking and Have Set the Prefix

    As long as you have a prefix set when using the DoubleClick code of GA, your tracking won’t work. Make sure that no prefix is set, if you want tracking to work perfectly with the DoubleClick code.

    Increase Timeout Values for VWO Async Code

    VWO Async code uses timeout values to execute the VWO code. If your website is getting significant traffic from mobile devices, we recommend increasing the timeout values as it will help users with slow internet connection to be part of the test. Also, we recommend that you add the VWO tracking code higher in the head section of the test page HTML code to reduce the execution time.  The timeout parameters in the VWO code are as follows:

  • settings_tolerance – default value is 2000 milliseconds (can be increased to 4000 milliseconds)

  • library_tolerance – default value is 2500 milliseconds (can be increased to 4000 milliseconds)

  • Apart from these reasons, there are many user specific scenarios for the gap between GA reports and VWO reports. Some of the reasons are as follows:

    • If the users have javascript disabled on their browsers, they are not included in the test.
    • If the users have cookies disabled on their browsers, they are not included in the test.
    • The URL(s) or patterns on which you are measuring traffic should match in both GA and VWO.
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