CAPTCHAs’ Effect on Conversion Rates – Are You Doing More Harm Than Good

SEOMoz puts out a good product and shares a lot of great data on different topics in SEO and the Internet as a whole. Today they had a post originally from their YouMoz blog (written by users of their service) and promoted to their main blog.

The author points out an serious issue with combating spam with Captchas.

We’ve all seen them, the often extremely hard to read random letters or words, aimed to combat spammers from junking up a site or a blog. Countless times we’ve all struggled to get them right.

The data the author is referring to in their post points out an alarming fact, that though the catchas are blocking spammers they might be also deterring legitimate comments.

This is not an easy issue to answer because the options are few. You can leave the captchas on and run the risk of having some people not leave comments because of it. You can also get rid of the captchas and just do more policing of the comments. Both have their pros and cons and honestly there doesn’t seem to be an easy answer.

There are other spam blocking programs out there, but what’s saying that these programs don’t block legitimate comments as well.

I’m curious what all of you think. Post your thoughts in the comments.

The case study was done over 50 different websites that I either manage or have access to. These websites range from less than 1 year old to over 5 years old. All forms were a collection of common information such as name, address, city, email address and a comment area.

The study was done over the course of 6 months, half of the website started with CAPTCHA’s on and the other half started with no CAPTCHA’s. After 3 months the CAPTCHA was switched to the other CAPTCHA setting. I recorded the amount of successful, failed, and SPAM conversions for each of the 50 web forms.

A SPAM conversion was recorded when the submission had excessive links or was a solicitation for a service. A failed conversion was recorded when a user/bot entered an incorrect CAPTCHA or never correctly entered the correct CAPTCHA after multiple tries. A successful conversion was when the information given in the web form was the required information minus any spammy information.

On to the data!!!!

CAPTCHA Turned Off

* 2,134 total conversions were entered while the CAPTCHA was off.

* 91 total SPAM conversions while the CAPTCHA was off.

* 0 total failed conversions while the CAPTCHA was off.


CAPTCHA Turned On* 2,156 total conversions were entered while the CAPTCHA was on.

* 11 total SPAM conversions while the CAPTCHA was on.

* 159 total failed conversions while the CAPTCHA was on.

From the data you can see that with CAPTCHA on, there was an 88% reduction in SPAM but there were 159 failed conversions. Those failed conversions could be SPAM, but they could also be people who couldn’t figure out the CAPTCHA and finally just gave up. With CAPTCHA’s on, SPAM and failed conversions accounted for 7.3% of all the conversions for the 3 month period. With CAPTCHA’s off, SPAM conversions accounted for 4.1% of all the conversions for the 3 month period. That possibly means when CAPTCHA’s are on, the company could lose out on 3.2% of all their conversions!

via SEOmoz | CAPTCHAs’ Effect on Conversion Rates.

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