Since CAPTCHA was first introduced, it has undergone various iterations and evolutions. With each step, the aim always has been to make it easier for humans and more challenging for non-humans to pass the test. Over time, this led to several different types of CAPTCHA checks being used.
CAPTCHA tests must also consider accessibility features such as screen readers used by visually impaired people. Since these function like a bot, it can make the entire process somewhat counterintuitive. Even so, this has been one of the motivators behind the evolution of CAPTCHA checks.
It is also important to note that CAPTCHA tests are offered by different vendors. Websites that offer such tests connect to the service provider who runs the actual tests. As such, you might not be able to find all different types of checks from any one vendor.
This article highlights the different types of CAPTCHA tests available. Some of the older versions have fallen out of favor as newer versions took over, offering better performance and accuracy.
Human-assisted OCR is one of the most known types of CAPTCHA tests, made popular by Google through their ReCAPTCHA service. It uses distorted text images, which users attempting to log in or fill out a form must decipher. The text used is scanned text that has failed OCR (Optical Character Recognition) and comes from sources such as Google Books. As such, solving this type of CAPTCHA keeps websites more secure and allows users to make valuable contributions to the literary world. Human-assisted OCR also includes an audio-equivalent, allowing hard-of-hearing users to complete the test.
No CAPTCHA, as the name suggests, is a CAPTCHA test that is invisible to the user. The test uses an algorithm that collects various data points about the user trying to log in or fill out a form. These data points can include how they move the mouse, whether they’re logged into their Gmail account etc. The user has to tick a checkbox titled I’m not a robot with the clicking itself taken into account as one of the data points.
Logic questions tests present the user with logic-based questions which they must complete. These questions are designed in such a way that a seven-year-old can complete them. Examples include working out single-digit additions and typing out numbers in digits.
In image recognition, users have to identify a specific object located in an image. These come in different flavors, including a single image that is split into sections using a grid and separate images displayed next to each other. Either way, the user has to make single or multiple selections depending on the question being asked to pass the test.
User interaction tests involve a simple interaction test such as moving a slider across the screen. While this might sound too simplistic, computers can have a hard time completing this type of test.
TYPE-IN is a CAPTCHA test that includes an advert with a related question that users must answer to pass the check. Questions usually involve typing some text that is directly tied to the advert. The main idea behind it is to kill two birds with one stone – increase website security through a CAPTCHA test while having another source of revenue.
The future of CAPTCHA checks
As technology continues to advance, CAPTCHA tests must evolve in response to continue telling humans and computers apart. While a few years ago, it would have been impossible for a computer to recognize a given image, advancements in deep learning have made this very possible. This is just one example of how CAPTCHA tests evolved due to technological advances.
Computing power is advancing at incredible rates obeying Moore’s law, where it doubles in power every year. My first computer was an Amiga 600. It had a single processor running at 7Mhz. Today, my computer has the equivalent of six processors, each running at 4500Mhz.
Current discussions on future CAPTCHAs include augmented reality, games, and puzzles like object rotation. However, as computers continue to evolve, there is no telling what the future of CAPCHAs will look like. This holds more true when you consider CAPTCHAs need to be universally solvable by humans – not an easy feat by any stretch of the imagination when you consider cultural and language constraints.
CAPTCHA checks for WordPress websites
CAPTCHA remains the best way to tackle spam and automated attacks. Thanks to CAPTCHA 4WP, adding CAPTCHA to your WordPress website is easier than ever before thanks to its intuitive user interface. It features numerous options and out-of-the-box integrations, helping you keep your site secure across the board.