Alternatives to Mathematical & Image Captcha's Needed by the Open Source Community



July 20, 2007

Example from MyCaptchaLike everyone else out there I'm sick of spam but like the idea of bringing user feedback to blog notes like this. I thought I'd list some alternatives to those wiggly letters that are so often inconsistently applied and are often difficult to read. CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart. Solving captchas should be fun, or at least less monotonous. I'd like to see these implemented in open source applications like Drupal and perhaps we'll get the time to do this ourselves at some time.

  • Type in the time displayed on an analog clock or type in the date of the day circled on the calendar (example code).
  • Correctly identify the animal or image displayed in the picture. This could be a select box that requires you to select as many entries as apply (if there is a picture of a puppy and five options you might need to select puppy and dog) - (pet example)
  • Identify the sound/video correctly - is the sound you hear when you click on the link from a dog, a cat, a rooster, a snake or a train?
  • Tie into a one question quiz related to the site with answers which your visitors will know or can guess (Captcha Riddler allows for this).
  • Hot or Not images could be applied easily to things like Environmentally Friendly or Not, and people could be asked to select which 3 of 9 images apply.
  • Riddles could be good, or identify what the stick person is doing
  • I do like the usefulness behind the reCAPTCHA program - so nice to do something useful when proving I'm not a bot
  • Enter your openid account to leave a comment - why not, everyone should have one.
  • Weather screen shot - pick the appropriate outfit for the weather today
  • Using a flash tool, arrange the blocks to create an image, word or order of operations

These are some options that could be used for a more interesting form of CAPTCHA. Remember machines like the predictable a lot more than people do. Variety is good, not just in your choice of fonts and background colors. Image based captcha's are pretty bad for accessibility issues, as are colour based ones. Trying to find tests to find the bots rather than the humans is useful too, setting up false form elements can be a useful way to do that.

About The Author

Mike Gifford is the founder of OpenConcept Consulting Inc, which he started in 1999. Since then, he has been particularly active in developing and extending open source content management systems to allow people to get closer to their content. Before starting OpenConcept, Mike had worked for a number of national NGOs including Oxfam Canada and Friends of the Earth.