How-To: Protect your Web Form from Spam with a Captcha

What is a captcha?

A captcha is a test designed to distinguish between humans and computers. In its most common form, it consists of an image of distorted letters that must be identified. While this test is quite easy to pass for a human, it is extremely difficult to solve programmatically. This makes it a very effective way to prevent automated scripts (a.k.a bots) from performing actions that are only intended for humans. This includes blocking spammers from abusing web forms with their spam bots.

How to add a captcha to your web form

Form Assembly users ^* can now easily add a captcha to their web form by following these simple steps:

• Go to your form’s display and processing properties page.
• Under the ‘Display and Hosting options’ you will find the ‘Spam Filter’ option. Check the box and save your change.
• If you are hosting the form on your own website, you will need to follow the instructions to install the form again, otherwise you are all set.

If you are not (yet) using the Form Assembly and still want to use captchas, you should look into Ed Elliot’s Captcha generation class (for PHP). Our captcha functionality is based on this library. It is powerful and very easy to use.

A few things to consider before using captchas

• It is somewhat of an annoyance for legitimate users.
• The test might be hard or even impossible to pass for people who are visually impaired. The Form Assembly provides an audio alternative, but this can also be challenging for some.
• If you need to comply with regulations regarding people with disabilities (such as section 508 for federal agencies in the US), you should not use captchas.

For the reasons mentioned above, it is best to not use captchas unless you are actively targeted by spammers or have another legitimate reason to do so.

If you have any comments or suggestions regarding this feature, please post it below, or in the support forum.

(*) Note: This service is not available on the free plan.

Technorati Tags: captcha, web forms, spam control