CAPTCHA is short for Completely Automatic Public Turing Test to Tell Computers and Humans Apart. The main purpose is to prevent abuse from spammers and bots. They're intended to be tests that humans can pass but computers cannot; i.e. humans can read distorted text but computer programs generally cannot.
According to an awesomely informative piece on CAPTCHAS from Smashing Magazine, a successful and logical CAPTCHA should be one or more of the following:
• A task that users excel at naturally but that computers can’t begin to comprehend,
• A task that is incredibly quick for users to perform but arduous for computers,
• A task that minimizes the need for additional user input,
• A task that is relatively accessible to all users, even those with special needs (that is, the CAPTCHA should be no more difficult than general Web usage and the current task demand).
The most popular type of CAPTCHA currently used is text recognition, the most popular example being Google's (sometimes questionable) program, reCAPTCHA.
Additionally, many CAPTCHAS are not accessible for all users, such as visually impared users who use assisted browsing tools. Cool graphics and motion-activated sliders may alienate more than a few users. Considering all the cons of using a CAPTCHA, it has been argued that it might be best not to use them at all, but rather find other more successful methods to stop spam.
Next week, we'll talk about how and why you should make your site accessible to users of all abilities. In the meantime, enjoy some (subjectively) awesome and uniquely creative CAPTCHAs.
1. Civil Rights CAPTCHA
Civil Rights Defenders is an organization who works hard to inform and empower the public about civil rights. In an effort to bring awareness of civil rights violations into everyday life, Civil Rights Defenders has created a CAPTCHA.
"Instead of visually decoding an image of distorted letters, the user has to take a stand regarding facts about human rights." Depending on the situation, the CAPTCHA generates three random adjectives portraying positive or negative emotions. Users must select how they feel about the situation. There is only one right answer.
Some have argued that this is manipulative and unfair. I might argue that that some of the adjectives are a wee bit bombastic. But if you feel anything other than "very crappy" about a human rights defender being abducted and murdered, well, then you don't really have much of a leg to stand on here.
Stop spam, draw shapes.
MotionCAPTCHA is a jQuery plugin " based on the HTML5 Canvas Harmony procedural drawing tool by Mr Doob and the $1 Unistroke Gesture Regonizer algorithm (and the more recent Protractor algorithm improvement).
It requires users to sketch the shape that they see in a box, in order to submit their form. I'm not sure how easy it is for bots to trace lines, but I do like the concept.
Best of all, your drawing doesn't have to be totally accurate, so don't fret. It looks great and has a lot of potential for use with touchscreens once the coding gets sorted out.
3. Tic Tac CAPTCHA
As easy as 1-2-3.
Fun Captcha is made to be - you guessed it - fun.
It's as simple as a game of Tic Tac Toe. Users are presented with games of Tic Tac Toe and asked to complete a game by getting three Xs in a row. Simple, right?
It's fun, easy and (almost) everyone knows how to play Tic Tac Toe. Best of all, it only requires one line of code. But have you ever played Tic Tac Toe against a computer? They always cheat.
4. Drag and Drop CAPTCHA
Keep unwanted guests out while staying classy.
Ajax Fancy Captcha is a fancy plugin that asks users to drag and drop specific items into a circle in order to verify their humanity.
The security level is "medium," but the clean design and friendlier aspects could make a nice fit for certain kinds of sites. Accessibility? Fuhgeddaboudit!
Stay classy, CAPTCHA fans, stay classy.
5. Slide and submit CAPTCHAs
Just slide to the right.
TheyMakeApps has a really nifty slide-y CAPTCHA.
In order to verify your human status, simply slide the bar over to the right. It asks users to “Show your human side; slide the cursor to the end of the line to create your account.”
While it's difficult for virtual intelligence to solve the slide, it probably wouldn't be too difficult to create a script to simply activate the "Submit" button.
The challenge then, lies in finding a way to make sliding CAPTCHAs accessible and not too easy for bots to bypass. Give it a little time, a little jQuery and a little elbow grease. I think there may be some real potential.