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Optimizely missing visitors

meganjdonnelly 05-19-16

Optimizely missing visitors

I have two experiments running right now where the # of visitors Optimizely is reporting is different from what is being reported by Marketo (both experiments are pointing to Marketo landing pages). 


For example:

- Optimizely reports 70 visitors, Marketo reports 275 - date range is the same.

- Optimizely reports 1,192 visitors, Marketo reports 1,766 - date range is the same.


I've confirmed that whenever we point to these URLs in campaigns we always include the .html at the end. We do always have additional tracking code after that, but I don't think that would affect the tracking... only if it were the other way around right? (i.e. if Optimizely tracked on the longer URL and we used the shorter version in campaigns)


Does anyone have any ideas why the visitor counts could be so off?


Thanks in advance!


David_Orr 05-23-16

Re: Optimizely missing visitors

Hi Megan,

Do you happen to know how Marketo calculates its user? Optimizely calculates visitors based off a unique visitor ID. This info is stored on a visitor's browser's cookie. This means a visitor can convert more than once but only attribute to 1 Unique Visitor or conversion.

There may be external factors that are causing "missing visitors". It is known that some ad blocking lists include Optimizely but may not include Marketo.

Senior Technical Support Engineer

Re: Optimizely missing visitors

Hi David - Marketo also uses cookies for tracking so each user can only be counted for one unique visit or conversion.


I can't imagine that ad blockers could account for such a large percentage of missing visitors. Is there any other possibility?