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Optimizely with Ad-Block

DuncanC 09-08-14

Optimizely with Ad-Block

Hi

 

Apologies if this has been posted / covered previously, but i can't find anything on this via google or the forum search.

 

It has been suggested by one of my colleagues that previously a question had been raised as to how Optimizely performs when a visitor has an ad blocker running on their browser (e.g. ABP or similar). 

 

Apparently it was believed that if an ad-blocked browser landed on an optimizely test, they would still be counted as participating in the test, but as the javascript was blocked they would just see the original version regardless (so they could be recorded as a 'B' test visitor, but only see the 'A' version of the page).  This would obviously have the effect of reducing the extent to which a test either won or lost, as it would encourage an unfair bias towards the baseline version of the page / content.

 

I would assume that Optimizely handles this simply by detecting that the script is blocked and handling the visit as null in terms of any tests running on the page, but can anyone just confirm this is the case?  or at least that ad-blocking doesn't introduce anomalies into our tests?

 

Many thanks!

Level 2

hbaecklund 09-08-14
 

Re: Optimizely with Ad-Block

Interesting!
Kathryn 09-08-14
 

Re: Optimizely with Ad-Block

Hi Duncan,

 

Really interesting question.

 

The answer will depend slightly on which adblock program you use, but to take Adblock Plus as an example, ABP has two mechanisms to block content on websites:

 

Element hiding: A CSS snippet is injected in the website to hide elements which should be blocked. The result is that ads are hidden from the page without impacting the structure of the site. However, these resources not prevented from loading.

 

Request blocking: Certain HTTP requests for retrieving resources will be prevented from loading completely.

 

In the latter instance, the visitor would not be bucketed and would not see an experiment at all, since Optimizely would be prevented from loading. In the former instance, it's possible that certain elements that had been modified using Optimizely would not be visible. Really it depends on the test setup. 

 

We don't have a fallback mechanism in place in situations where adblockers block the Optimizely CDN snippet, because all the variables needed to do so are defined in that snippet. However, in my experience, adblockers tend not to block the snippet unless a special filter has been set up by the user to do so. This has to do with the fact that users tend to test essential portions and elements on their site using Optimizely, which are elements that are not generally hidden using the element hiding mechanism.

 

Best wishes,

Kathryn

Optimizely
DuncanC 09-08-14
 

Re: Optimizely with Ad-Block

[ Edited ]

Hi

 

Thanks for the reply!

 

I set up a little test this afternoon to investigate this - and results were as you described (not that i doubted you Smiley Happy)

 

I chose a page on our site that was no longer included in the nav, and which hadn't seen any traffic for at least 6 months (an old product landing page previously used for PPC).  I ran a quick test to remove the hero image on this page, with 100% of the traffic pointed at the variation.

 

I accessed the test 3 times using Chrome; once with no blockers in place, once with Adblock-Plus active, and once with both Adblock-Plus and Ghostery active within the browser.  I left both ABP and Ghostery on standard 'fresh install' settings as i figure that's what the majority would use, and cleared cookies etc between visits. 

 

Ghostery claims to detect and block the Optimizely snippet by default, whereas ABP doesnt make any mention of blocking it (so i assume it doesn't).

 

Results as follows:

 

Clean Browser -  Variation shown, 1 Visitor, 1 Goal

ABP - Variation shown, 1 Visitor, 1 Goal

ABP and Ghostery - Original shown, no visit recorded, no goal recorded

 

So basically it looks like it works fine, with the caveat that anyone with Ghostery or another equally stringent blocking tool wont be included in any optimizely-driven tests.  Which is fine as far as i'm concerned, as at least this doesn't skew results.

 

 

 

 

Level 2
Kathryn 09-10-14
 

Re: Optimizely with Ad-Block

Interesting! Thanks for going ahead and looking into this further :-) I'm sure this will be very helpful to other people who are curious about the effect of adblocking programs on their Optimizely tests.
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