I think that captchas will drive away some of your visitors. Captchas are irritating, annoying and damage user experience.
Most of the times, Captchas are used to prevent spammers to use automated programs to insert spam into your websites. This is a good reason to use a captcha as long as it is effective against spam.
I am doubting whether a captcha will give long lasting protection. The hackers are winning battle after battle and captcha breakers are evolving very quickly.
Captchas and negative user experience
A captcha is a picture with random letters and numbers. The user must type these figures into an input field. Only if these typed-in figures are similar to the figures on the picture, the user will be send to the next page.
The reason behind all this is to prevent automated programs, such as spambots, from posting messages containing advertisement links and other spammy content.
Since the spambots were getting smarter, captchas got more difficult to read. An example is the picture above.
- The figures have different colors resembling the background.
- The figures are transparent and diagonal.
- The background texture resembles the texture of the figures.
- It is not clear which figures are caps.
- Is the third figure an “o” or a “q”? And what about the last figure “7″, you would almost overlook it.
As far as I am concerned, such unreadable captchas would cost you visitors.
Use readable captchas that are difficult to bots
Since the captcha is one of the most important and trusted measures against spam, programmers love to decode them.
For example sam.zoy.org is working actively on a captcha decoder. This page presents many examples of captchas including the percentage of good guesses made by the bot which can be as high as 100%. Captcha-info.org provides a list of software that is able to break captchas. For the real technical persons read the following post on hacking the gmail captcha.
If you decide to nevertheless use captchas to protect your site, try to minimize user interference. I was surprised to see that some captchas that are considered pretty good are nevertheless easy to read. Look for example at the captchas below.
You will find more captchas at sam.zoy.org and Wikimedia. If you would like to add captchas to your own website you may find guidance, captcha scripts and captcha generators at captcha-info.org.
If you can not beat them, use them
Veldhuizen van Zanten uses the captcha to have visitors type in business names of sponsors instead of random figures, based on an old post of Seth Godin. You can see the implementation on his weblog thenextweb.org.
Alternatives for a captcha
I am working on a post with alternatives for a captcha. I expect to publish it in the next coming days. I am not sure whether these alternatives work as good as the captchas but hopefully they are more practical for the visitors to use.
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I am a Dutch guy working to make a business out of the internet. On this weblog I share my finds about usability and searchability doing my best to avoid second language writing...
I do agree that captchas are annoying! you wont even notice that it says Enter 9+4 here on some sites unless you get an error later!