The 42nd Estate

Ah, captchas, the bane of many internet users around the globe. Sometimes they work, sometimes they don’t, but nearly always they annoy your visitors.

For those who don’t know, captchas are those verification fields on web forms that you must pass before your comment gets published or email gets sent. They usually take the form of an image with text or a simple math equation or question you must answer. They’re designed to prevent spammers from bogging down the web site owner’s email inbox or comment queue, but in the end they just serve to push humans away while still letting a lot of spam bots through.

Comment Captcha Fail

While comment captchas might seem like a great idea, the problem is they often fail. Either they’re too loose and let the spam bots in or they’re too tough and discourage real human users from posting. I’ve found the Akismet plugin does a good enough job keeping the spam out that there’s no need for comment captchas.

But on super high traffic sites, I can see the benefit of a properly implemented captcha that keeps 90% of the spammers out while discouraging only 10% of the human users. In such a scenario, a captcha can be a positive. Unfortunately, many sites use captchas when they really don’t need to, or implement them so poorly that they fail at all goals.

Check out the below captcha that Orble uses after a visitor writes a comment on one of their sites.

Orble Captcha Fail

Now, there’s a few reasons this captcha fails. The first thing you should notice is a big black and white fuzzy box. That box should display an image of some text for the user to input to prove they’re human (spam bots have a tough time reading images, though they’re getting better). Instead, we just get a lot of fuzz.

Clearly, Orble knew their captcha was full of fail because below the box where the image text should be they have a very helpful bit of information.

If you cannot read the letters in the image type in “nwvghp”

Well, that’s awfully kind of Orble to list the letters we need to type in if we can’t see the image, the problem is spam bots can read text too. Listing the image letters in text on the same page completely defeats the purpose of a captcha.

Don’t Annoy Non-Spamming Humans

In other words, all that this particular captcha system does is add an additional step for human commenters. Oh, and it also discourages people from commenting on the Orble blogs. It might even cause bloggers to lose comments if people don’t see the bit of text giving them the input code and just assume the captcha is broken and move on.

So, take a lesson from Orble and don’t implement comment captcha systems that fail. If you must use a captcha, ensure that it’s easily decipherable and has options for users who cannot read (e.g. a sound clip of the letters). But, the best scenario is to simply ditch the captcha and implement other spam prevention methods that don’t annoy human visitors.

The first goal of any captcha system should not be to block as much spam as possible. Instead, it should be designed with the valid human user in mind. Implement a system that is clean and easily navigated by humans. Otherwise, you’ll just annoy all your human visitors and likely won’t stop that many spammers.

Tags: comments, interface

This entry was posted on Tuesday, June 2nd, 2009 at 2:58 am and is filed under Blogging Tips. You can follow any responses to this entry through the RSS 2.0 feed.You can leave a response, or trackback from your own site.